Skip to main content
PLOS One logoLink to PLOS One
. 2020 Jun 18;15(6):e0234923. doi: 10.1371/journal.pone.0234923

Associations of childhood experiences and methamphetamine use among Akha and Lahu hill tribe youths in northern Thailand: A cross-sectional study

Tawatchai Apidechkul 1,2,*, Chalitar Chomchoei 3, Pilasinee Wongnuch 2, Ratipark Tamornpark 1, Panupong Upala 1, Fartima Yeemard 1, Marisa Poomiphak Na Nongkhai 2, Woottichai Nachaiwieng 2, Rachanee Sunsern 2
Editor: Siyan Yi4
PMCID: PMC7302480  PMID: 32555604

Abstract

Background

Methamphetamine (MA) is a commonly used substance among youths, particularly those who are living in poor economic conditions with low levels of education and who have had bad childhood experiences. The Akha and Lahu hill tribe youths living on the Thailand-Myanmar-Laos border are identified as the group most vulnerable to MA use in Thailand. The study aimed to estimate the prevalence of MA use and determine its associations with childhood experiences among Akha and Lahu youths aged 15–24 years in northern Thailand.

Methods

A cross-sectional study was performed. Validated and sealed questionnaires were used to gather information from participants after obtaining the informed consent form. Questionnaires were completed by participants and their parents at home. Logistic regression was used to identify the associations between variables at the α = 0.05 level.

Results

A total of 710 participants participated in the study: 54.2% were Akha, 52.5% were females, 50.6% were aged 15–17 years, and 11.4% did not have Thai identification card (ID) cards. The overall prevalence of MA use at least once among Akha and Lahu youths was 14.5%. After controlling for all potential confounding factors, 8 variables were found to be associated with MA use. Males had a greater chance of MA use than females (AOR = 4.75; 95% CI = 2.27–9.95). Participants aged 21–24 years had a greater chance of MA use than those aged 15–17 years (AOR = 2.51; 95% CI = 1.11–5.71). Those who had a family member who used MA had a greater chance of MA use than those who did not (AOR = 5.04; 95% CI = 1.66–15.32). Those who had been physically assaulted by a family member while aged 0–5 years had a greater chance of MA use than those who had not (AOR = 2.29; 95% CI = 1.02–5.12). Those who had been physically assaulted by a family member while aged 6–14 years had a greater chance of MA use than those who had not (AOR = 3.15; 95% CI = 1.32–7.54). Those who had a close friend who used alcohol had a greater chance of MA use than those who did not (AOR = 2.24; 95% CI = 1.24–4.72). Those who had a highly confident personality had a greater chance of MA use than those who did not (AOR = 2.35; 95% CI = 1.17–4.69), and those who smoked had a greater chance of MA use than those who did not (AOR = 8.27; 95% CI = 4.42–15.46).

Conclusions

All relevant government and nongovernment agencies together with the Ministry of Public Health Thailand should address MA use among Akha and Lahu youths by properly developing a community health intervention that lowers risk of MA use by addressing family relationships, male youth behaviors, and focused on those individuals with a highly confident personality.

Introduction

Methamphetamine (MA) has been widely recognized as the original factor contributing to several problems from individual health problems to social problems, including physical and mental health problems [1], poor family relationships [2], social problems [3], and interference with country economic growth [4]. Today, MA use is resulting in large social and economic problems globally [5]. Many communities have faced a severe stage of problems associated with MA use, particularly disruption of community economic growth [6]. The United Nations Office on Drugs and Crime (UNODC) reported that 5.6% (275 million people) of the global population aged 15–64 years used drugs at least once in 2016 [7]. In 2018, a study reported that MA was the second most commonly used illicit drug worldwide, and the Southeast Asia region was the most impacted region, including Thailand [8]. In 2019, the Department of Mental Health Ministry of Public Health, Thailand reported that there were 2.7 million Thai youths using MA [9]. Northern Thailand is considered a region of MA production and distribution due to sharing borders with Myanmar and Laos, which are recognized as the largest regions of MA production in the world [10]. Today, MA is becoming easily available in these areas due to the decrease in its price, particularly in border areas [11].

The most vulnerable group for MA use is the youth group [12]. Youths range in age from 15–24 years according to the definition of the United Nations [13]. Youths with poor socioeconomic status are reported as the group most vulnerable to MA use in Thailand, and this is particularly true among hill tribe youths [14]. The hill tribe is a group of people who have migrated into Thailand from southern China over several centuries [15] which is consisted of six main tribes: Akha, Lahu, Yao, Karen, Hmong, and Lisu [16]. The United Nations reported that most of the hill tribe people in Thailand lived below the poverty level in Thailand [17]. Akha is the largest group, followed by Lahu [16]. These two groups accounted for more than 70.0% [18] of the total hill tribe populations in Thailand, which was 3.5–4 million in 2018 [19]. Akha and Lahu have their own culture, language, and lifestyle pattern, including attitudes and perceptions toward drugs. Most Akha and Lahu villages are settled along the hill and border areas of Thailand-Myanmar and Thailand-Laos; therefore, it is not difficult for villagers to access MA.

Childhood experiences are widely studied in various populations in different aspects, including health problems [20]. In 2014, a study in China reported that some childhood experiences were associated with MA use in adulthood [21]. A study in the United States also reported that childhood experience and household dysfunction were associated with many health problems at later ages, including death in adults [22]. People begin using MA for different purposes, such as to have fun, to get more energy to work or to be accepted by peers [23]. Akha and Lahu youths begin using MA for several reasons, such as persuasion from their peers and level of access drugs [24]. However, there is no study detecting the associations between childhood experiences and MA use, particularly in hill tribe youths in Thailand, who are recognized as one of the most vulnerable populations for MA use.

Therefore, the study aimed to estimate the prevalence of MA use and determine the association of childhood experience with MA use among Akha and Lahu youths aged 15–24 years who lived in northern Thailand. The findings could be used to develop public health interventions for reducing MA use among Akha and Lahu hill tribe youths in Thailand.

Methods

Study design

A cross-sectional study design was applied to collect data from the selected participants.

Study population

The study population included Akha and Lahu youths aged 15–24 years who lived in Chiang Rai Province, Thailand, in 2019.

Study sample

The study sample was composed of Akha and Lahu youths aged 15–24 years who lived in Chiang Rai Province in 2019 and were randomly selected for the study. However, those who could not identify themselves as members of the Akha or Lahu tribes were excluded from the study. Moreover, both participants and parents who could not provide essential information regarding the study protocols were also excluded from the study.

Sample size

The sample size was calculated by the standard formula for a cross-sectional study design [25]. After the calculation, based on the assumption of p = 0.27 [26], q = 0.73, and e = 0.05, there were 670 participants required for the analysis: approximately 335 for the Lahu tribe and another 335 for the Akha tribe.

Since, there is no scientific data available on the prevalence of the MA use among the hill tribe population, then, the calculation for the sample size was based on the information (prevalence) from the study conducted in Thai youth who lived in the central of Bangkok which was conducted by Toeam, et al [26]. Moreover, based on the information of the number of populations between the Akha and Lahu which was reported by the Hill tribe Welfare and Development Center [18], two tribes had similar size of the population living in 243 Akah villages (approximately 60,000 population) and 216 Lahu villages (approximately 50,000 population).

Steps of data collection

In 2018, there were 243 Akha villages and 216 Lahu villages in Chiang Rai Province. Ten villages from each tribe were randomly selected by a simple random method. Government officers who were responding to the selected villages were asked for approval to perform the study in the targeted villages. After obtaining approval for access to the villages from the district officers, cooperation from the village headmen was obtained before collecting data. The lists of youths aged 15–24 years in the selected villages were obtained from the village headmen. All eligible individuals according to the lists received from the village headman were invited to participate in the study: 496 people from 10 Akha villages and 518 people from 10 Lahu villages. Appointments were made five days before assessing the participants to complete the questionnaire.

All participants were provided all information regarding the study protocols, particularly the security of the information obtained from all participants. Informed consent was obtained before completion of the questionnaire. Questionnaires were packed and sealed before being provided to the participants. Questionnaires were completed by participants in a personal private place and returned to researchers the next day. All questions in part one, two, four, five, and six were completed by participants (children) including part of socio-economic status of the family (part two), and nobody knew the content before reaching to researcher. However, questions in part three were separated and completed by their parents. A few people could not completely use Thai, then they were interviewed by researcher to complete the questionnaire. The reason to collect the information on experience of violence during individual’s aged 0–5 years, from parents was to improve the quality of the information. This protocol was proved from the pilot phase. The process of completion of the questionnaire was blinded, and no information could be referred back to any individual. The questionnaires were sent back to the researcher on the next day and completely sealed. All questionnaires were destroyed properly after coding. Data file was kept with security code.

Research instruments

The questionnaire was developed based on the literature and discussion with five experts who were working in the fields of youth and child behaviors (3 people) and behaviors related to MA use (2 people) including the findings from our previous study [24]. The questionnaire consisted of six parts. In part one, 10 questions were used to collect data on general information such as age, sex, tribe, marital status, etc. In part two, 16 questions were used to collect information on the family, such as the relationship of the parents, number of family members, monthly family income, etc. In part three, 11 questions were used to collect an individual’s experience from 0–5 years of age, including abuse experience, such as history of assault and abuse from family members, abuse from peers in school, and sexual abuse. In this section, all information was obtained from the parents. In part four, 13 questions were used to collect information on history of being assaulted or abused while aged 6–14 years, including a history of school expulsion, assault by family members, assault by their peers, etc. In part five, 26 questions were used to collect information on personal behaviors such as smoking behavior, alcohol use, amphetamine use, etc. In part six, 20 questions were used to collect information on knowledge and attitude toward MA use. At the end of questionnaire, it appeared a short question on asking the experience in use of MA.

Subsequently, the questionnaire was examined for content validity by the item-objective congruence (IOC) technique, which was executed by three external experts in relevant fields: public health, psychology, and psychiatry. The feasibility and reliability of the questionnaire were detected by piloting with 10 selected Akha youths (5 males and 5 females) and another 10 selected Lahu youths (5 males and 5 females). The questionnaires were conducted three (3) times in the same piloting samples before being ready for use in the field. The sequencing and appropriateness of the questions were tested in the first and second rounds of the pilot. The last round was aimed at testing the reliability, which was found to have a Cronbach’s alpha of 0.78. The process of filling the questionnaire lasted 25 minutes for youth and 10 minutes for parents.

Statistical analysis

Data were coded and double entered into an Excel file. Data files were transferred into SPSS version 24 (SPSS, Chicago, IL) for analysis. Descriptive data analysis was performed; categorical data were described in percentages. The means and its standard deviations (SDs) were used to describe the characteristics of continuous data. Logistic regression was used to detect the associations of childhood experiences with MA use among the Akha and Lahu youths at the significance level of alpha 0.05. The “Enter” mode was used in the step of selection independent variables into the statistical model. The pseudo R2 of Cox-Snell R2 and Nagelkerke R2, and the Hosmer- Lemshow chi-square were used to determine the fit of the model in all steps. Some variables were controlled the effect in the model which were determined as the confounder factors for the prediction. In the final model, all significant variables and controlled variables were fitted before making interpretations.

Ethical approval and consent to participate

All research concept, procedures, and instruments were approved by the Mae Fah Luang University Research Ethic Committee on Human Research (REH-60141). Participants were asked their wiliness to participate the study by obtaining written informed consent form before completion the questionnaire in a private and confident room. Among those participants aged less than 18 years, parents were asked to agree in providing information in the questionnaire on behalf of their children by signing on the informed consent.

Results

The participation rate was 77.6% (385 out of 496) in Akha, and 62.7% (325 out of 518) in Lahu. A total of 710 participants participated in the study; 54.2% were Akha, 52.5% were females, 50.6% were aged 15–17 years (mean = 18.1, SD = 2.7), and 11.4% did not have Thai ID cards. The majority were single (91.8%) and Christian (60.1%). Most participants had a high school and lower education (84.8%), lived with their parents (63.7%), and had 4–6 family members (66.9%) (Table 1).

Table 1. General characteristics of the participants.

Characteristics Total n (%) Akha n (%) Lahu n (%)
Total 710 (100.0) 385 (54.2) 325 (45.8)
Sex
 Male 337 (47.5) 190 (49.4) 147 (45.2)
 Female 373 (52.5) 195 (50.6) 178 (54.8)
Age (years)
 15–17 359(50.5) 208 (54.0) 151 (46.5)
 18–20 216 (30.4) 119 (30.9) 97 (29.8)
 21–24 135 (19.0) 58 (15.1) 77 (23.7)
Mean = 18.04, SD = 2.67
Marital status
 Single 652(91.8) 372 (96.6) 280 (86.2)
 Married 55(7.5) 12 (3.1) 43 (13.2)
 Other 3(0.3) 1 (0.3) 2 (0.6)
Religion
 Buddhist 283(39.9) 128 (33.2) 155 (47.7)
 Christian 427(60.1) 257 (66.8) 170 (52.3)
Education
 No educated 71(10.0) 22 (5.7) 49 (15.1)
 Primary school 76(10.7) 18 (4.7) 58 (17.8)
 Secondary school 163(23.0) 87 (22.6) 76 (23.4)
 High school 292(41.1) 209 (54.3) 83 (25.5)
 Vocational and university 108(15.2) 49 (12.8) 59 (18.2)
Occupation
 Student 448(63.1) 288 (74.8) 160 (49.2)
 Employed 126(17.7) 50 (12.9) 76 (23.4)
 Agriculturist 17(2.4) 8 (2.1) 9 (2.8)
 Unemployed 119(16.8) 39 (10.1) 80 (24.6)
Thai identification (ID) card
 Yes 629(88.6) 339 (88.1) 290 (89.2)
 No 81(11.4) 46 (11.9) 35 (10.8)
Village location
 Rural 352(49.6) 176 (45.7) 176 (54.2)
 Semi-urban 358(50.4) 209 (54.3) 149 (45.8)
Living with
 Parents 452(63.7) 241 (62.6) 211 (64.9)
 Father 49(6.9) 29 (7.5) 20 (6.2)
 Mother 86(12.1) 59 (15.3) 87 (8.3)
 Stepfather or stepmother 19(2.7) 16 (4.2) 3 (0.9)
 Relatives 104(14.6) 40 (10.4) 64 (19.7)
Parents’ status
 Married and living together 510(71.8) 272 (70.6) 238 (73.2)
 Either father or mother died 61(8.6) 38 (9.9) 23 (7.1)
 Both father and mother died 13(1.8) 6 (1.5) 7 (2.2)
 Separated 60(8.5) 38 (9.9) 22 (6.7)
 Divorced 66(9.3) 31 (8.1) 35 (10.8)
Number of family members (people)
 ≤ 3 119(16.8) 65 (16.9) 54 (16.6)
 4–6 475(66.9) 246 (63.9) 229 (70.5)
 ≥ 7 116(16.3) 74 (19.2) 42 (12.9)
Family income per month (baht)
 ≤ 10,000 213(30.0) 104 (27.0) 109 (33.5)
 10,001–20,000 44(6.2) 26 (6.8) 18 (5.5)
 ≥ 20,001 44(6.2) 32 (8.3) 12 (3.7)
 Unknown 409(57.6) 223 (57.9) 186 (57.3)

More than half of the participants had a family member who smoked (52.4%) and used alcohol (56.3%), while a few participants had a family member who used other substances. In the comparison analysis in experiences of family members on exposing to drugs and alcohol use between two tribes, it was found that no variable was found statistical significance (Table 2).

Table 2. Experiences of family members on exposing to drugs and alcohol.

Exposure Total Akha Lah χ2 (p-value)
n % n % n %
Having family member who ever smoked
 No 338 47.6 191 49.6 147 45.2 1.36 (0.244)
 Yes 372 52.4 194 50.4 178 54.8
Having family member who ever used alcohol
 No 310 43.7 158 41.0 152 46.8 2.35 (0.125)
 Yes 400 56.3 227 59.0 173 53.2
Having family member who ever used glue
 No 690 97.2 378 98.2 312 96.0 3.07 (0.080)
 Yes 20 2.8 7 1.8 13 4.0
Having family member who ever used methamphetamine
 No 684 96.3 371 96.4 313 96.3 0.02 (0.968)
 Yes 26 3.7 14 3.6 12 3.7
Having family member who ever used heroin
 No 696 98.0 377 97.9 319 98.2 0.05 (0.825)
 Yes 14 2.0 8 2.1 6 1.8
Having family member who ever used opium
 No 687 96.8 376 97.7 311 95.7 2.18 (0.140)
 Yes 23 3.2 9 2.3 14 4.3

*Significant level at α = 0.05

The majority of caregivers while the participants were aged 0–5 years were mothers (72.4%), and most of the participants were supported by their family (58.2%). A few people had accidents (16.8%) and were hospitalized (29.4%) due to a health problem. Eighty-seven participants (12.3%) were assaulted by family members, and 15.6% were assaulted by peers in school. While having a comparison between tribes in the potential exposures relevant to MA use while aged 0–5 years, four variable were found the statistical differences; main care giver (p-value = 0.014), having accident (p-value = 0.035), having been hospitalized (p-value = 0.015), and having been physically assaulted by peer in school (p-value = 0.025) (Table 3).

Table 3. Potential exposures relevant to MA use while aged 0–5 years.

Family information Total Akha Lahu χ2 (p-value)
n % n % n %
Main caregiver
 Mother 514 72.4 268 69.6 246 75.7 14.34 (0.014*)
 Father 87 12.3 62 16.1 25 7.7
 Stepfather 10 1.4 3 0.8 7 2.2
 Stepmother 11 1.5 7 1.8 4 1.2
 Other relative 88 12.4 45 11.7 43 13.2
Used to be greatly supported by parents in regard to receiving desired food and beverages
 No 644 90.7 354 91.9 290 89.2 1.54 (0.214)
 Yes 66 9.3 31 8.1 35 10.8
Used to travel to desired places with support from parents
 No 556 78.3 306 79.5 250 76.9 0.68 (0.410)
 Yes 154 21.7 79 20.5 75 23.1
Used to be greatly supported by parents in regard to desired clothes and other items
 No 610 85.9 339 88.1 271 83.4 3.17 (0.075)
 Yes 100 14.1 46 11.9 54 16.6
Accident
 No 591 83.2 310 80.5 281 86.5 4.46 (0.035*)
 Yes 119 16.8 75 19.5 44 13.5
Hospitalization
 No 501 70.6 257 66.8 244 75.1 5.88 (0.015*)
 Yes 209 29.4 128 33.2 81 24.9
Head injury
 No 600 84.5 326 84.7 274 84.3 0.02 (0.893)
 Yes 110 15.5 59 15.3 51 15.7
Physically assaulted by family member
 No 623 87.7 337 87.5 286 88.0 0.04 (0.850)
 Yes 87 12.3 48 12.5 39 12.0
Physically assaulted by peer in school
 No 599 84.4 314 81.6 285 87.7 5.03 (0.025*)
 Yes 111 15.6 71 18.4 40 12.3

*Significant level at α = 0.05

While participants were in the age range of 6–14 years, 65.4% were cared for by their mother, and few people had been supported by their family in regard to getting desirable food (5.2%) and travelling to desirable places (8.2%). Almost one-third had a head injury (16.2%). A few people were assaulted by family members (8.5%), assaulted due to their sexual orientation (4.1%), assaulted due to their socioeconomic status by their peers in school (12.1%), and sexually abused (1.3%). In the comparison analysis between tribes in the aspect of having the potential exposures relevant to MA use while aged 6–14 years, three (3) variable were found the statistical differences; having had travelled to desired places with support from parents (p-value = 0.02), had been greatly supported by parents in regards to desired clothes and other items (p-value = 0.048), and failed class examination (p-value = 0.010) (Table 4).

Table 4. Potential exposures relevant to MA use while aged 6–14 years.

Exposure Total Akha Lahu χ2 (p-value)
n % n % n %
Main caregiver
 Mother 464 65.4 250 64.9 214 65.8 6.25 (0.283)
 Father 113 15.9 70 18.2 43 13.2
 Stepfather 7 1.0 2 0.5 5 1.5
 Stepmother 15 2.1 8 2.1 7 2.2
 Relatives 111 15.6 55 14.3 56 17.3
Used to be greatly supported by parents in regard to receiving desired food and beverages
 No 673 94.8 367 95.3 306 94.2 0.49 (0.484)
 Yes 37 5.2 18 4.7 19 5.8
Travelled to desired places with support from parents
 No 652 91.8 365 94.8 287 88.3 9.92 (0.002*)
 Yes 58 8.2 20 5.2 38 11.7
Had been greatly supported by parents in regard to desired clothes and other items
 No 45 6.3 367 95.3 298 91.7 3.92 (0.048*)
 Yes 665 93.7 18 4.9 27 8.3
Accident
 No 578 81.4 311 80.8 267 82.2 0.22 (0.639)
 Yes 132 18.6 74 19.2 58 17.8
Hospitalization
 No 557 78.5 293 76.1 264 81.2 2.74 (0.098)
 Yes 153 21.5 92 23.9 61 18.8
Head injury
 No 595 83.8 315 81.8 280 86.2 2.44 (0.118)
 Yes 115 16.2 70 18.2 45 13.8
Expulsion from school
 No 693 97.6 374 97.1 319 98.2 0.77 (0.380)
 Yes 17 2.4 11 2.9 6 1.8
Assaulted by family member
 No 650 91.5 354 91.9 296 91.1 0.17 (0.678)
 Yes 60 8.5 31 8.1 29 8.9
Assaulted by peer in school
 No 622 87.6 330 85.7 292 89.8 2.77 (0.096)
 Yes 88 12.4 55 14.3 33 10.2
Insulted due to sexual orientation
 No 681 95.9 372 96.6 309 95.1 1.08 (0.300)
 Yes 29 4.1 13 3.4 16 4.9
Insulted due to socioeconomic status
 No 624 87.9 339 88.1 285 87.7 0.02 (0.884)
 Yes 86 12.1 46 11.9 40 12.3
Sexually abused
 No 697 98.2 379 98.4 318 97.8 0.35 (0.555)
 Yes 13 1.8 6 1.6 7 2.2
Failed class examination
 No 420 59.2 211 54.8 209 64.3 6.59 (0.010*)
 Yes 290 40.8 174 45.2 116 35.7

*Significant level at α = 0.05

One hundred and three participants (14.5%) reported that they had used MA at least once in their life, 18.5% smoked, and 36.1% used alcohol. Most participants used Facebook (93.5%) and the Line application (73.8%). More than one-fourth (25.9%) had their urine tested for MA by police officer, and 7.6% had been arrested. Most participants had ≤5 close friends (78.6%), and of those close friends; 18.0% smoked, 27.5% used alcohol, and 2.1% used MA. The majority had an active and talkative personality (63.2%), were social (81.3%), and had high self-confidence (70.4%). While in the comparisons between tribes in behaviors and personalities, twelve (12) variables were found the statistical differences; regularly exercise (p-value = 0.001), ever played online games (p-value = 0.001), ever used Facebook (p-value = 0.001), frequency of Facebook use (p-value = 0.001), ever used the Line application (p-value = 0.004), ever tested for MA in urine by police officer (p-value<0.001), number of close friends (p-value<0.001), close friend who drink alcohol (p-value = 0.039), close friend who uses MA (p-value = 0.030), personality (p-value = 0.017), highly self-confident behavior (p-value = 0.014), and socialized behavior (p-value = 0.032) (Table 5).

Table 5. Participants’ behaviors and personality.

Characteristics Total Akha Lahu χ2(p-value)
n % n % n %
Ever used MA at least once
 No 607 85.5 330 85.7 277 85.2 0.03 (0.855)
 Yes 103 14.5 55 14.3 48 14.8
Ever smoked
 No 579 81.5 307 79.7 272 83.7 1.83 (0.176)
 Yes 131 18.5 78 20.3 53 16.3
Ever used alcohol
 No 454 63.9 235 61.0 219 67.4 3.08 (0.079)
 Yes 256 36.1 150 39.0 106 32.6
Regularly exercise
 No 90 12.7 29 7.5 61 18.8 20.10 (0.001*)
 Yes 620 87.3 356 92.5 264 81.2
Ever played online games
 No 298 42.0 138 35.8 160 49.2 12.97 (0.001*)
 Yes 412 58.0 247 64.8 165 50.8
Ever used Facebook
 No 46 6.5 13 3.4 33 10.2 13.36 (0.001*)
 Yes 664 93.5 372 96.6 292 89.8
Frequency of Facebook use (n = 664)
 Sometimes 145 21.8 58 15.6 87 29.8 24.73 (0.001*)
 Often 203 30.6 110 29.6 93 31.8
 Everyday 316 47.6 204 54.8 112 38.4
Ever used the Line Application
 No 186 26.2 84 21.8 102 31.4 8.34 (0.004*)
 Yes 524 73.8 301 78.2 223 68.6
Frequency of use of the Line Application (n = 524)
 Sometimes 202 38.5 117 38.9 85 38.1 1.87 (0.392)
 Often 175 33.4 94 31.2 81 36.3
 Everyday 147 28.1 90 29.9 57 25.6
Experienced a broken heart
 No 339 47.7 181 47.0 158 48.6 0.18 (0.670)
 Yes 371 52.3 204 53.0 167 51.4
Used to work in the night-work sector
 No 688 96.9 375 97.4 313 96.3 0.70 (0.402)
 Yes 22 3.1 10 2.6 12 3.7
Used to have sex in exchange for items or money
 No 700 98.6 377 97.9 323 99.4 2.72 (0.099)
 Yes 10 1.4 8 2.1 2 0.6
Ever tested for MA in urine by police officer
 No 526 74.1 257 66.8 269 82.8 23.55 (<0.001*)
 Yes 184 25.9 128 33.2 56 17.2
Arrested
 No 656 92.4 357 92.7 299 92.0 0.13 (0.716)
 Yes 54 7.6 28 7.3 26 8.0
Number of close friends (people)
 ≤ 5 558 78.6 280 72.7 278 85.5 17.33 (<0.001*)
 6–10 141 19.9 98 25.5 43 13.2
 ≥ 11 11 1.5 7 1.8 4 1.2
Close friend who smokes
 No 582 82.0 306 79.5 276 84.9 3.53 (0.060)
 Yes 128 18.0 79 20.5 49 15.1
Close friend who drinks alcohol
 No 515 72.5 267 69.4 248 76.3 4.28 (0.039*)
 Yes 195 27.5 118 30.6 77 23.7
Close friend who uses glue
 No 695 97.9 379 98.4 316 97.2 1.25 (0.264)
 Yes 15 2.1 6 1.6 9 2.8
Close friend who uses heroin
 No 701 98.7 382 99.2 319 98.2 1.60 (0.205)
 Yes 9 1.3 3 0.8 6 1.8
Close friend who uses MA
 No 695 97.9 381 99.0 314 96.6 4.69 (0.030*)
 Yes 15 2.1 4 1.0 11 3.4
Personality
 Polite and quiet 200 28.2 100 26.0 100 30.8 8.20 (0.017*)
 Active and talkative 449 63.2 260 67.5 189 58.2
 Stay alone 61 8.6 25 6.5 36 11.1
Highly self-confident behavior
 No 210 29.6 99 25.7 111 34.2 6.03 (0.014*)
 Yes 500 70.4 286 74.3 214 65.8
Socialized behavior
 No 133 18.7 61 15.8 72 22.2 4.61 (0.032*)
 Yes 577 81.3 324 84.2 253 77.8

* Significant level at α = 0.05

In the univariate analysis that was performed to identify factors associated with MA use among the Akha and Lahu hill tribe youths, there were several factors associated with MA use, such as sex, age, occupation, parents’ marital status, number of family members, family member smoking status, family member alcohol use, and family member amphetamine use (Table 6).

Table 6. Univariate and multivariate analyses of factors associated with MA use among Akha and Lahu youths.

Factor MA use Univariate analysis Multivariate analysis
Yes No OR 95% CI p-value AOR 95% CI p-value
n % n %
Total 103 14.5 607 85.5 N/A N/A N/A N/A N/A N/A
Sex
 Male 91 27.0 246 73.0 11.13 5.97–20.76 <0.001* 4.75 2.27–9.95 <0.001*
 Female 12 3.2 361 96.8 1.00 1.00
Age (years)
 15–17 35 9.7 324 90.3 1.00 1.00
 18–20 35 16.2 181 83.8 1.79 1.08–2.96 0.023* 1.90 0.98–3.69 0.059
 21–24 33 24.4 102 75.6 3.00 1.77–5.06 <0.001* 2.51 1.11–5.71 0.028*
Tribe
 Akha 55 14.3 330 85.7
 Lahu 48 14.8 277 85.2 1.04 0.68–1.58 0.855
Marital status
 Single 96 14.7 556 85.3 1.00
 Married 6 10.9 49 89.1 2.90 0.26–32.25 0.387
 Other 1 33.3 2 66.7 0.71 0.30–1.70 0.441
Religion
 Buddhist 44 15.5 239 84.5 1.00
 Christian 59 13.8 368 86.2 0.87 0.57–1.33 0.522
Education
 Non-educated 19 26.8 52 73.2 4.39 0.53–36.04 0.169
 Primary school 20 26.3 56 73.7 4.23 0.52–35.10 0.175
 Secondary school 21 12.9 142 87.1 1.78 0.22–14.36 0.591
 High school 36 12.3 256 87.7 1.69 0.21–13.37 0.620
 Vocational and university 7 6.5 101 93.5 1.00
Occupation
 Student 37 8.3 411 91.7 1.00
 Employed 31 24.6 95 75.4 3.66 2.13–6.31 <0.001*
 Agriculturalist 4 23.5 13 76.5 3.42 1.03–10.98 0.040*
 Unemployed 31 26.1 88 73.9 3.91 2.30–6.65 <0.001*
Thai identification card
 Yes 97 15.4 532 84.6 1.00
 No 6 7.4 75 92.6 2.28 0.97–5.38 0.060
Village location
 Rural 45 12.8 307 87.2 1.00
 Semiurban 58 16.2 300 83.8 1.32 0.87–2.01 0.197
Parents’ marital status
 Living together 57 11.2 453 88.8 1.00
 Either father or mother died 15 24.6 46 75.4 2.59 1.36–4.94 0.004*
 Both father and mother died 1 7.7 12 92.3 0.66 0.09–5.19 0.695
 Separated 16 26.7 44 73.3 2.89 1.53–5.45 0.001*
 Divorced 14 21.2 52 78.8 2.14 1.12–4.10 0.022*
Number of family members (people)
 ≤ 3 25 21.0 94 79.0 3.16 1.41–7.11 0.005*
 4–6 69 14.5 406 84.5 2.02 0.98–4.18 0.058
 ≥ 7 9 7.8 107 92.2 1.00
Family income per month (baht)
 ≤ 10,000 37 17.4 176 82.6 1.00
 10,001–20,000 7 15.9 37 84.1 0.90 0.37–2.17 0.815
 ≥ 20,001 6 13.6 38 86.4 0.75 0.30–1.01 0.547
 Unknown 53 13.0 356 87.0 0.71 0.45–1.12 0.139
Having a family member who smokes
 No 30 8.9 308 91.1 1.00 1.59–3.95 <0.001*
 Yes 73 19.6 299 80.4 2.51
Having a family member who uses alcohol
 No 34 11.0 276 89.0 1.00
 Yes 69 17.3 331 82.8 1.69 1.09–2.63 0.019*
Having a family member who uses glue
 No 93 13.5 597 86.5 1.00
 Yes 10 50.0 10 50.0 6.42 2.60–15.84 <0.001*
Having family member who uses methamphetamine
 No 89 13.0 595 87.0 1.00 1.00
 Yes 14 53.8 12 46.2 7.80 3.50–17.40 <0.001* 5.04 1.66–15.32 0.004
Having a family member who uses heroin
 No 98 14.1 598 85.9 1.00
 Yes 5 35.7 9 64.3 3.39 1.11–10.33 0.032*
Having a family member who uses opium
 No 95 13.8 592 86.2 1.00
 Yes 8 34.8 15 65.2 3.32 1.37–8.05 0.008*
Main caregiver from the ages of 0–5 years
 Mother 63 12.3 451 87.7 1.00
 Father 17 19.5 70 80.5 1.74 0.96–3.14 0.067
 Stepfather 4 40.0 6 60.0 4.77 1.31–17.38 0.018
 Stepmother 3 27.3 8 72.7 2.69 0.69–10.39 0.153
 Other relative 16 18.2 72 81.8 1.59 0.84–3.01 0.153
Used to be greatly supported in regard to receiving desirable food and beverage from parents while aged 0–5 years
 No 11 16.7 55 83.3 1.00
 Yes 92 14.3 552 85.7 1.20 0.61–2.38 0.601
Used to be greatly supported by parents in regard to travelling to desirable places while aged 0–5 years
 No 27 17.5 127 82.5 1.00
 Yes 76 13.7 480 86.3 1.34 0.83–2.17 0.230
Used to be greatly supported by parents in regard to clothes and other items while aged 0–5 years
 No 23 23.0 77 77.0 1.00
 Yes 80 13.1 530 86.9 1.98 1.17–3.33 0.010*
Had accident while aged 0–5 years
 No 75 12.7 516 87.3 1.00
 Yes 28 23.5 91 76.5 2.12 1.30–3.45 0.003*
Had been hospitalized while aged 0–5 years
 No 72 14.4 429 85.6 1.00
 Yes 31 14.8 178 85.2 1.04 0.66–1.64 0.874
Had head injury while aged 0–5 years
 No 83 13.8 517 86.2 1.00
 Yes 20 18.2 90 81.8 1.38 0.81–2.37 0.235
Had been physical assaulted by family member while aged 0–5 years
 No 77 12.4 546 87.6 1.00 1.00
 Yes 26 29.9 61 70.1 3.02 1.80–5.07 <0.001* 2.29 1.02–5.21 0.045*
Had been physical assaulted by peer in school while aged 0–5 years
 No 77 12.9 522 87.1 1.00
 Yes 26 23.4 85 76.6 2.07 1.58–3.42 0.004*
Major caregiver while aged 6–14 years
 Mother 55 11.9 409 88.1 1.00
 Father 20 17.7 93 82.3 1.60 0.91–2.80 0.100
 Stepfather 3 42.9 4 57.1 5.58 1.21–25.58 0.027*
 Stepmother 7 46.7 8 53.3 6.51 2.27–18.65 <0.001*
 Relatives 18 16.2 93 83.8 1.64 0.88–3.07 0.121
Used to be greatly supported in regard to receiving desirable food and beverage from parents while aged 6–14 years
 No 8 21.6 29 78.4 1.00
 Yes 95 14.1 578 85.9 1.68 0.75–3.78 0.211
Had been greatly supported by parents to travel to desirable places while aged 6–14 years
 No 15 25.9 43 74.1 1.00
 Yes 88 13.5 564 86.5 2.24 1.19–4.19 0.012*
Had been greatly supported by parents in regard to clothes and other items while aged 6–14 years
 No 96 14.4 569 85.6 1.00
 Yes 7 15.6 38 84.4 1.09 0.47–2.52 0.837
Had accident while aged 6–14 years
 No 79 13.7 499 86.3 1.00
 Yes 24 18.2 108 81.8 1.14 0.85–2.32 0.186
Had been hospitalized while aged 6–14 years
 No 76 13.6 481 86.4 1.00
 Yes 27 17.6 126 82.4 1.36 0.84–2.19 0.214
Had head injury while aged 6–14 years
 No 78 13.1 517 86.9 1.00
 Yes 25 21.7 90 78.3 1.84 1.11–3.05 0.017*
Had been expelled from school while aged 6–14 years
 No 92 13.3 601 86.7 1.00
 Yes 11 64.7 6 35.3 11.98 4.33–33.17 <0.001*
Had been physically assaulted by family member while aged 6–14 years
 No 80 12.3 570 87.7 1.00 1.00
 Yes 23 38.3 37 61.7 4.43 2.50–7.84 <0.001* 3.15 1.32–7.54 0.010*
Had been physically assaulted by peer in school while aged 6–14 years
 No 81 13.0 541 87.0 1.00
 Yes 22 25.0 66 75.0 2.23 1.30–3.81 0.003*
Had been insulted due to sexual orientation while aged 6–14 years
 No 97 14.2 584 85.8 1.00
 Yes 6 20.7 23 79.3 1.57 0.62–3.96 0.338
Had been insulted due to socioeconomic status while aged 6–14 years
 No 78 12.5 546 87.5 1.00
 Yes 25 29.1 61 70.9 2.87 1.70–4.84 <0.001*
Was sexually abused while aged 6–14 years
 No 96 13.8 601 86.2 1.00
 Yes 7 53.8 6 46.2 7.30 2.40–22.20 <0.001*
Failed a class examination while aged 6–14 years
 No 62 14.8 358 85.2 1.00 0.69–1.61 0.087
 Yes 41 14.1 249 85.9 1.05 0.69–1.61 0.087
Number of close friends (people)
 ≤ 5 77 13.8 481 86.2 1.00
 6–10 23 16.3 118 83.7 2.12 0.73–2.02 0.447
 ≥ 11 3 27.3 8 72.7 2.23 0.61–9.02 0.216
Having a close friend who smokes
 No 51 8.8 531 91.2 1.00
 Yes 52 40.6 76 59.4 7.12 4.52–11.23 <0.001*
Having a close friend who drinks alcohol
 No 57 11.1 458 88.9 1.00 1.00
 Yes 46 23.6 149 76.4 2.48 1.61–3.81 <0.001* 2.42 1.24–4.72 0.009*
Having a close friend who uses glue
 No 96 13.8 599 86.2 1.00
 Yes 7 46.7 8 53.3 5.46 1.93–15.40 0.001*
Having a close friend who uses heroin
 No 96 13.7 605 86.3 1.00
 Yes 7 77.8 2 22.2 22.06 4.52–107.75 <0.001*
Having a close friend who uses MA
 No 88 12.7 607 87.3 1.00
 Yes 15 100.0 0.0 5.46 1.93–15.40 0.001*
Personality
 Polite and quiet 25 4.0 601 96.0 1.00
 Active and talkative 54 90.0 6 10.0 0.96 0.58–1.59 0.865
 Stays alone 24 3.8 601 96.2 4.54 2.34–8.81 <0.001*
Highly self-confident personality
 No 20 9.5 190 90.5 1.00 1.00
 Yes 83 16.6 417 83.4 1.89 1.23–3.17 0.016* 2.35 1.17–4.69 0.016*
Plays online games
 No 27 9.1 271 90.9 1.00
 Yes 76 18.4 336 81.6 2.27 1.42–3.62 0.001*
Exercise regularly
 No 24 26.7 66 73.3 1.00
 Yes 79 12.7 541 87.3 0.40 0.24–0.68 0.001*
Smokes
 No 34 5.9 545 94.1 1.00 1.00
 Yes 69 52.7 62 47.3 17.84 10.96–29.05 <0.001* 8.27 4.42–15.46 <0.001*
Uses alcohol
 No 20 4.4 434 95.6 1.00
 Yes 83 32.4 173 67.6 10.41 6.20–17.50 <0.001*
Used to use a “Facebook” application
 No 3 6.5 43 93.5 1.00
 Yes 100 15.1 564 84.9 2.54 0.77–8.35 0.124
Used to use a “Facebook” application
 No 26 7.7 313 92.3 1.00
 Yes 77 20.8 294 79.2 3.15 1.97–5.06 <0.001*
Used to work in a night-work sector
 No 95 13.8 593 86.2 1.00
 Yes 8 36.4 14 63.6 3.57 1.46–8.73 0.005*
Used to have sex in exchange for items or money
 No 99 14.1 601 85.9 1.00
 Yes 4 40.0 6 60.0 4.05 1.12–14.60 0.033*
Has been arrested
 No 69 10.5 587 89.5 1.00
 Yes 34 63.0 20 37.0 14.46 7.89–26.51 <0.001*
Knowledge on the impacts of MA use
 Low 45 17.7 209 82.3 3.55 0.82–15.35 0.089
 Moderate 56 13.3 365 86.7 2.53 0.59–10.84 0.120
 High 2 5.7 33 94.3 1.00
Attitude on the impacts of MA use
 Low 48 22.7 163 77.3 4.42 2.02–9.68 <0.001*
 Moderate 47 12.7 324 87.3 2.18 1.00–4.74 0.005*
 High 8 6.3 120 93.8 1.00

*Significance level α = 0.05

After controlling for tribe, marital status, religion, education, occupation, and having Thai ID card in the multivariate model, 8 variables were found to be associated with MA use among the Akha and Lahu youths in northern Thailand: sex, age, having a family member who used MA, having been physical assaulted by family member while aged 0–5 years, having been physical assaulted by family member while aged 6–14 years, having a close friend who drinks alcohol, having a highly confident personality, smoking.

Males had a 4.75-fold (95% CI = 2.27–9.95) greater chance of MA use than females. Participants aged 21–24 years had a 2.51-fold (95% CI = 1.11–5.71) greater chance of MA use than those aged 15–17 years. Those who had a family member who used MA had a 5.04-fold (95% CI = 1.66–15.32) greater chance of MA use than those who did not. Those who had been physically assaulted by a family member while aged 0–5 years had a 2.29-fold (95% CI = 1.02–5.21) greater chance of MA use than those who had not. Those who had been physically assaulted by a family member while aged 6–14 years had a 3.15-fold (95% CI = 1.32–7.54) greater chance of MA use than those who had not. Those who had a close friend who used alcohol had a 2.24-fold (95% CI = 1.24–4.72) greater chance of MA use than those who did not. Those who had a highly confident personality had a 2.35-fold (95% CI = 1.17–4.69) greater chance of MA use than those who did not, and those who smoked had a 8.27-fold (95% CI = 4.42–15.46) greater chance of MA use than those who did not (Table 6).

Discussion

Among the Akh and Lahu hill tribe youths who are living in northern Thailand, there was a high prevalence (14.5%) of MA use. There were also several factors related to MA use including personal characteristics, personality, family member and peer behaviors, and childhood experiences. Being male, being older, smoking, and having a highly confident personality were risk factors for using MA. Those who had a family member who used MA and had a close friend who used alcohol had a greater risk of using MA than those who did not. Childhood experiences of physical assault by a family member while aged 0–5 or 6–14 years were also associated with MA use among Akha and Lahu youths aged 15–24 years.

The prevalence of MA use among the youths who were studying in a vocational school in northern Thailand [27] was reported as 8.8%. This shows that the prevalence of MA use among the hill tribe youths (14.5%) is greater than that among the youths who were living in northern Thailand. It was also greater than the prevalence of MA use reported in Cambodia (10.4%) [28]. A greater proportion of MA use among the Akha and Lahu youths while comparing with Thai population, it could be supported by a qualitative study presented that social norms and also other positive personal perceptions among the Akha and Lahu were acting as major contributors for MA use in these population [24].

In our study, it was found that males had a significantly greater risk of using MA than females, which is consistent with a study conducted in Myanmar, which reported that males had a greater prevalence of MA users than females [29]. However, Dluzen et al [30] and Rungnirundorn et al [31] reported that females were more likely to be MA users and significantly more likely to be MA-dependent than males. This might be because in the culture of the Akha and Lahu hill tribe people, males dominate all activities at the family and community levels; therefore, males could expose to and use MA more than females [24].

In this study, it was also found that people aged 18–20 years had a greater risk of using MA than the youngest Akha and Lahu youths. This could be because older youths have income from work, and they could afford to use MA. Moreover, older youths may have many more close friends from socializing, and the opportunities to begin using MA could be greater than those among younger youths. The World Health Organization (WHO), Thailand, reported that Thai youths experienced their first use of drugs before the age of 14 years [32]. A study in Malaysia in 2018 [33] also reported that the age of beginning MA use was 13 years, which supports our finding. A report from a national survey on drug use and health in the United States in 2015 also reported that the early age of MA use was 12 years [34]. However, a study in Australia in 2019 [35] reported that among youths in Australia, the first use of MA occurred at 20 years, which is different from our study.

Smoking was found to be associated with MA use among Akha and Lahu youth in Thailand. This finding was supported by a study in Thailand that reported that smoking was significantly associated with the initiation of MA use among youths [27]. A study in Morocco also reported that smoking behavior was associated with MA use among high school children [36]. Moreover, in a review of an epidemiologic study in 2016 [37], it was found that smoking behaviors were greatly associated with MA use. In a systematic review, it was presented that smoking was a major predictor for MA use in various age categories [38].

A highly self-confident personality was also found to be associated with MA use among Akha and Lahu youths in Thailand. This finding could be explained by the fact that those who have high confidence would have a chance to engage in a new experience in their life, particularly in the use of MA among the Akha and Lahu youths. Due to youths being in a stage of life in which they are very eager to know their environment along with access to MA and a low education, youths can become MA users. This concept is supported by studies conducted in Taiwan [39] and in the United States [40]. However, a study in Iran reported the idea that a highly self-confident personality type was a protective factor for MA use [41]. However, the Alcohol and Drug Abuse Institute (ADAI) reported that those who had low confidence had a greater risk of initiating MA use among American people [42].

Having a family member who uses MA was greatly significantly associated with MA use among Akha and Lahu youths in Thailand. This is supported by a study by Chomchoie et al. [24]. The systematic review study clearly showed an association between a family history of drug use and MS use among youths [38].

A study in the United States reported that physical abuse before 15 years of age was a key factor associated with MA use and MA-related violence [40]. Moreover, a study in Morocco reported that living with an unsecure family was associated with MA use among youths [36]. Peltzer et al. [43] demonstrated that being a victim of physical assault, particularly by family members, was associated with MA use among youths in Asia. In our study, it was found that those children had been physical assaulted either during age of 0–5 years or 6–14 years or both periods had a greater chance of MA use that those who did not. A total of 108 cases were reported in having physical assaulted by family member from whole participants; 87 cases reported on age of 0–5 years, and 60 cases were reported on aged of 6–14 years. Among the victims, 38 out of 109 cases (34.8%) had experienced on physical assaulted by family member in both periods.

This may be children in childhood need to get love and care from people living around them particularly from their parents and family members to grow strong both physical and mental health. Children who grew up with love and safe environment, it could motivate to get desired outcomes in later years of age such as not use MA [44, 45].

In our study, it was found that children those who had a close friend who used alcohol had a greater chance of MA use than those who did not. This is supported by a study in the United Stated which was reported that those children who had a close friend who used alcohol had a greater chance to initiate MA than those who did not significantly [46]. A longitudinal study in rural cities, Wester United States, it was found that those adolescents who had a close friend who used alcohol was associated with substance use especially MA [47]. Moreover, a qualitative study in Thailand was also reported that having close friend who used alcohol led children to initiate MA [48].

Some limitations have been found in the study. First, identifying those people who used MA was difficult because it is an illegal substance in Thailand; therefore, most people who are using MA would not identify themselves as MA users. However, with the method of no information being traced back to any individual after filling in the questionnaire and the double-check method used by public health volunteers in a community to identify participants who used MA, the information gathered on the outcome would be closely related to the actual outcome. Under the current Thai government policy, all villagers have to be identified and classified in regard to whether they are using MA or not by their peers and an anonymous method. Those who are using MA are asked to participate in MA treatment programs in villages. This program is now working particularly well in rural villages and is managed by the Ministry of Public Health and other stakeholders [49]. Second, in part three of the questionnaire, questions were used to collect individual experience information related to when the participants were aged 0–5 years, particularly information related to physical assault by family members. These questions were answered by their parents, and the outcomes were shown to have high accuracy in the pilot test. Finally, three participants provided incomplete questionnaires, and they were excluded from the analysis. This small proportion of missing data would not interfere with the interpretation of the information.

Conclusion

The study clearly shows the strong associations between childhood experiences while aged 0–14 years and personal behaviors and MA use among Akha and Lahu youths of older age in northern Thailand. Compared with other groups, male sex, smoking, older age, having close friends who use alcohol, and having a family member who uses MA were associated with MA use. Moreover, those who experienced physical assault from family members while aged 0–14 years were likely to use MA at a later age. Integrated intervention programs are urgently needed to reduce MA use among Akha and Lahu youths in Thailand; these programs should focus on improving family relationships and male individuals, smokers, and people with a highly confident personality. Moreover, the implementation should be focused in regularly monitoring and prevention on the physical assaulted during childhood by family members. The practical guideline on basic action while facing a problem of the physical assaulted in children by family members for the community health volunteers should be developed and provided. Strong collaborations among relevant agencies, both government and nongovernment, within countries and between counties are needed to address this problem.

Supporting information

S1 File. Questionnaire used in the study.

(PDF)

S2 File. Data file of the study.

(XLSX)

Acknowledgments

We would like to thank the National Research Council of Thailand (NRCT), Mae Fah Luang University (MFU), and The Center of Excellence for the Hill Tribe Health Research in support grant for doing this project. We also would like to extend our thank to community leaders and participants in their cooperation along the process of data collection.

Data Availability

Data is fully available in supporting information file.

Funding Statement

Funding was provided by the National Research Council of Thailand (NRCT) (Grant No.29/2561). NRCT has no role and involving any step of conducting this research.

References

  • 1.Darke S, Kaye S, McKetin R, Duflou J. Major physical and psychological harms of methamphetamine use. Drug and Alcohol Review. 2008; 27(3): 253–62. 10.1080/09595230801923702 [DOI] [PubMed] [Google Scholar]
  • 2.Dyba J, Moesgen D, Klein M, Pels F, Leyendecker B. Evaluation of a family-oriented parenting intervention for methamphetamine involved mothers and fathers: The SHIFT parent training. Additive Behaviors Reports; 2019; 9 10.1016/j.abrep.2019.1000173 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Garbraith N. The methamphetamine problem commentary on psychiatric morbidity and socio-occupational dysfunction in residents of a drug rehabilitation centre. BJPsych Bull. 2015; 39(5): 218–220 10.1192/pb.bp.115.050930 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Drug Policy Research Center. The economic cost of methamphetamine use in the United States, 2005. https://www.rand.org/content/dam/rand/pubs/monographs/2009/RAND_MG829.pdf. Assessed 31 Oct 2019
  • 5.Guyll M, Spoth R, Crowley DM. Economic analysis of methamphetamine prevention effcts and employer costs. J Stud Alcohol Drugs. 2011; 72(4): 577–85 10.15288/jsad.2011.72.577 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 6.Watt MH, Meade CS, Kimani S, MacFarlane JC, Choi KW, Skinner D, et al. The impact of methamphetamine (“tik”) on a peri-urban community in Cape Tow, South Africa. Int J Drug Policy. 2013; 25(2): 219–225. 10.1016/j.drugpo.2013.10.007 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 7.United Nations Office on Drugs and Crime. World drug report 2018. https://www.unodc.org/wdr2018/prelaunch/WDR18_Booklet_1_EXSUM.pdf. Assessed 29 Oct 2019
  • 8.Stoneberg DM, Shukla RK, Magness MB. Global Methamphetamine trends: an evolving problem. International Criminal Justice Review. 2018; 28(2): 136–161 [Google Scholar]
  • 9.Department of Mental Health, Ministry of Public Health. Behavior of youths in Thailand, 2019. https://www.dmh.go.th/news-dmh/view.asp?id=28478. Assessed 9 Nov 2019
  • 10.ASEAN Narcotics Cooperation Center. ASEAN drug monitoring report 2017. https://asean.org/storage/2016/10/Doc-3-ADM-Report-2017-as-of-16-Aug18-FINAL.pdf. Assessed 29 Oct 2019
  • 11.Cacia R, Lwin TM. Methamphetamine use in Myanmar, Thailand and Southern China: assessing practices, reducing harms. Drug Policy Briefing. 2019. Available from: www.tni.org/files/publication-downloads/dpb_50_eng_16022019_web_2.pdf. Assessed 9 Nov 2019 [Google Scholar]
  • 12.The Transnational Institute. Methamphetamine use in Myanmar, Thailand and Southern China: assessing practices, reducing harms. https://www.tni.org/files/publication-downloads/dpb_50_eng_16022019_web_2.pdf. Assessed 29 Oct 2019
  • 13.United Nation. Definition of Youth. https://www.un.org/esa/socdev/documents/youth/fact-sheets/youth-definition.pdf. Assessed 29 Oct 2019
  • 14.The Narcotic Control Management Center, Ministry of Public Health. Trends of drugs in 2019. http://ncmc.moph.go.th. Assessed 31 Oct 2019
  • 15.Princess Maha Chakri Siridhorn Anthropology center. Hill tribe. http://www.sac.or.th/main/index.php. Assessed 30 Oct 2019
  • 16.Apidechkul T. Health situation of Akha hill tribe in Chiang Rai Province, Thailand. J Pub Health Sev. 2016; 14(1): 77–97. [Google Scholar]
  • 17.United Nations Country Team in Thailand. Thailand common country assessment. https://www.undp.org/content/dam/rbap/docs/programme-documents/cca/TH-CCA-2016.pdf. Assessed 30 Oct 2019
  • 18.The Hill Tribe Welfare and Development Center. Hill tribe population The hill tribe welfare and development center. Chiang Rai: Ministry of Interior; 2018. p. 23–29. [Google Scholar]
  • 19.Lukas H. Southeast Asian hill tribes and the opium trade—The historical and social-economic background of the marginalization of minorities using the example of Thailand. Austria: University of Vienna; p. 2017. [Google Scholar]
  • 20.UCL Institute of Health Equality. The impact of adverse experiences in the home on the health of children and young people. http://www.instituteofhealthequity.org/resources-reports/the-impact-of-adverse-experiences-in-the-home-on-children-and-young-people/impact-of-adverse-experiences-in-the-home.pdf. Assessed 9 Nov 2019
  • 21.Ding Y, Lin H, Zhou L, Yan H, He N. Adverse childhood experiences and interaction with methamphetamine use frequency in the risk of methamphetamine-associated psychosis. Drug Alcohol Depend. 2014; 142: 295–300. 10.1016/j.drugalcdep.2014.06.042 [DOI] [PubMed] [Google Scholar]
  • 22.Felitti VJ, Anda RF, Nordenberg D, Williamson DF, Sipitz AM, Wdwards V, et al. Relationship of childhood abuse and household dysfunction to many of the leading causes of death in adults. The Adverse Childhood Experiences (ACE) Study. Am J Prev Med. 1998; 14(4): 245–58. 10.1016/s0749-3797(98)00017-8 [DOI] [PubMed] [Google Scholar]
  • 23.DiMiceli LE, Sherman SG, Aramrattana A, Sirirojn B, Celentano DD. Methamphetamine use is associated with high levels of depressive symptoms in adolescents and young adults in Rural Chiang Mai Province, Thailand. BMC Public Health. 2016; 16:168 10.1186/s12889-016-2851-1 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24.Chomchoei C, Apidechkul T, Wongnuch P, Tamornpark R, Upala P, Nongkhai MP. Perceived factors influencing the initiation of methamphetamine use among Akha and Lahu youths; a qualitative approach. BMC Public Health. 2019; 19:847 10.1186/s12889-019-7226-y [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 25.Arya R., Antonisamy B., Kumar S., (2012). Sample size estimation in prevalence studies. Indian J Pediatr. 2012; 79(11): 1482–88 10.1007/s12098-012-0763-3 [DOI] [PubMed] [Google Scholar]
  • 26.Toeam A, Lapvongwatana P, Chansatitporn N, Chamroonsawasdi K. Predictive factors of amphetamine use among youths in a congested community. Thai Red Cross Nursing Journal. 2016; 9(2): 88–103. [Google Scholar]
  • 27.Chomsri P, Aramratana A, Siviroj P, Kuntawee S. prevalence of substance used, and associated between substances used with sensation seeking among vocational students. Nursing Journal. 2017; 44(2): 172–81. [Google Scholar]
  • 28.Mburu G, Tuot S, Mum P, Chhoun P, Navy C, Yi S. Prevalence and correlates of amphetamine-type stimulant use among transgender women in Cambodia. International Journal of Drug Policy. 2019; 74: 136–43 10.1016/j.drugpo.2019.09.010 [DOI] [PubMed] [Google Scholar]
  • 29.Saw YM, Saw TN, Yasuoka J, Chan N, Kham NPE, Khine W, et al. Gener difference in early initiation of methamphetamine use among current methamphetamine users in Muse, Northern Shan State, Myanmar. BMC Harm Reduction Journal. 2017; 14: 21 10.1186/s12954-017-0147-0 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 30.Dluzen DE, Liu B. Gener differences in methamphetamine use and responses: a review. Gender Med. 2008; 5(1): 24–35. [DOI] [PubMed] [Google Scholar]
  • 31.Rungnirundorn T, Verachai V, Gelernmter J, Malison RT, Kalayasiri R. Sex difference in methamphetamine use and dependence in a Thai treatment center. J Addict Med. 2017; 11(1): 19–27. 10.1097/ADM.0000000000000262 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 32.World Health Organization (WHO). Thailand 2015: Global school-based student health surver. http://origin.who.int/ncds/surveillance/gshs/Thailand-GSHS-2015-Report.pdf. Assessed 9 Nov 2019
  • 33.Chooi WT, Zaharim NM, Desrosiers A, Ahmad I, Yasin MA, Jaapar SZ, et al. Early initiation of amphetamine-type stimulants (ATS) use associated with lowered cognitive performance among individulas with co-occuring opioid and ATS usew disorders in Malaysia. J Psychoactive Drugs. 2017; 49(4): 326–32. 10.1080/02791072.2017.1342152 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 34.Substance Abuse and Mental Health Services Administration. National survey on drug use and health: Monthly variation in substance use initiation among full-time colleagues’ students. 2015. www.samhsa.gov/data/sites/default/files/report_2049/ShortReport-2049.pdf. Assessed 9 Nov 2019
  • 35.Chan GC, Butterworth P, Becker D, Degenhardt L, Stockings E, Hall W, et al. Longitudinal patterns of amphetamine use from adolescence to adulthood: a latent class analysis of a 20-years prospective study of Australians. Drug and Alcohol Dependence. 2019; 194: 121–7. 10.1016/j.drugalcdep.2018.08.042 [DOI] [PubMed] [Google Scholar]
  • 36.Zarrouq B, Bendaou B, Aris AE, Achour S, Rammouz I, Aalouane R, et al. Psychoactive substances use and associated factors among middle and high school students in the North Center of Morocco: a cross-sectional questionnaire survey. BMC Public Health; 2016; 16:468 10.1186/s12889-016-3143-5 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 37.Weinberger AH, Funk AP, Goodwin RD. A review of epidemiologic research on smoking behavior among persons with alcohol and illicit substance use disorders. Preventive Medicine. 2016; 92: 148–59 10.1016/j.ypmed.2016.05.011 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 38.Russell K, Dryden DM, Liang Y, Frieses C, O’Gorman K, Durec T, et al. Risk factors for methamphetamine use in youth: a systematic review. BMC Pediatr. 2008; 8: 48 10.1186/1471-2431-8-48 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 39.Ma CH, Lin KF, Chen TT, Yu YF, Chien HF, Huang WL. Specific personality traits and associated psychosocial distresses among individuals with heroin or methamphetamine use disorder in Taiwan. Journal of the Formosan Medical Association. 10.1016/j.jfma.2019.08.026 [DOI] [PubMed] [Google Scholar]
  • 40.Brecht ML, Herbeck D. Methamphetamine use and violet behavior: user perceptions and predictors. J Drug Issues. 2013; 43(4): 468–82 10.1177/0022042613491098 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 41.Angoorani H, Narenjiha H, Tayyebi B, Ghassabian A, Assari S. Amphetamine use and its associated factors in body builders: a study from Tehran, Iran. Archives of medical Science. 2012; 8. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 42.Alcohol and Drug Abuse Institute (ADAI), University of Washington, United State. Methamphetamine in Washington, 2018. https://adai.uw.edu/pubs/pdf/2018MethamphetamineInWashington.pdf. Assessed 9 Nov 2019
  • 43.Peltzer K, Pengpid S. Cannabis and amphetamine use among adolescents in five Asian countries. Central Asian Journal of Global Health. 2017; 6:1 10.5195/cajgh.2017.288 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 44.Bethell C, Jones J, Gombojav N, Linkenbach J, Sege R. Positive childhood experiences and adult mental and relational health in statewide sample. JAMA Pediatrics. 2019; 173(1): e193007. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 45.Sege RD, Browne CH. Responding to ACEs with HOPE: health outcomes from positive experiences. Academic Pediatrics. 2017; 17(7S): S79–85. 10.1016/j.acap.2017.03.007 [DOI] [PubMed] [Google Scholar]
  • 46.Pedersen W, Sandberg S, Copes H. High speed: amphetamine use in the context of conventional culture. Deviant Behaviors. 2015; 36: 146–65. [Google Scholar]
  • 47.Branstetter SA, Low S, Furman W. The influence of parents and friends on adolescent substance use: a multidimensional approach. J Subst Use. 2011; 16(2): 150–60. 10.3109/14659891.2010.519421 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 48.Sherman SG, german D, Sirirojn B, Thompson N, Aramrattana A, Celentano DD. Initiation of methamphetamine use among young Thai drug users: a qualitative study. J Adolesc Health. 2008; 42(1): 36–42. 10.1016/j.jadohealth.2007.07.002 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 49.Nacotics Control Management Center, Ministry of Public Health. Methamphetamine treatment project. http://ncmc.moph.go.th. Assessed 9 Nov 2019

Decision Letter 0

Siyan Yi

13 Mar 2020

PONE-D-20-01893

Associations of childhood experiences and methamphetamine use among Akha and Lahu hill tribe youths in northern Thailand: A cross-sectional study

PLOS ONE

Dear Dr. Apidechkul,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

We would appreciate receiving your revised manuscript by Apr 27 2020 11:59PM. When you are ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter.

To enhance the reproducibility of your results, we recommend that if applicable you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). This letter should be uploaded as separate file and labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. This file should be uploaded as separate file and labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. This file should be uploaded as separate file and labeled 'Manuscript'.

Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.

We look forward to receiving your revised manuscript.

Kind regards,

Siyan Yi, MD, MHSc, PhD

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements:

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at http://www.plosone.org/attachments/PLOSOne_formatting_sample_main_body.pdf and http://www.plosone.org/attachments/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. We suggest you thoroughly copyedit your manuscript for language usage, spelling, and grammar. If you do not know anyone who can help you do this, you may wish to consider employing a professional scientific editing service.  

Whilst you may use any professional scientific editing service of your choice, PLOS has partnered with both American Journal Experts (AJE) and Editage to provide discounted services to PLOS authors. Both organizations have experience helping authors meet PLOS guidelines and can provide language editing, translation, manuscript formatting, and figure formatting to ensure your manuscript meets our submission guidelines. To take advantage of our partnership with AJE, visit the AJE website (http://learn.aje.com/plos/) for a 15% discount off AJE services. To take advantage of our partnership with Editage, visit the Editage website (www.editage.com) and enter referral code PLOSEDIT for a 15% discount off Editage services.  If the PLOS editorial team finds any language issues in text that either AJE or Editage has edited, the service provider will re-edit the text for free.

Upon resubmission, please provide the following:

  • The name of the colleague or the details of the professional service that edited your manuscript

  • A copy of your manuscript showing your changes by either highlighting them or using track changes (uploaded as a *supporting information* file)

  • A clean copy of the edited manuscript (uploaded as the new *manuscript* file)

3. Please address the following:

- Please include additional information regarding the survey or questionnaire used in the study and ensure that you have provided sufficient details that others could replicate the analyses. For instance, if you developed a questionnaire as part of this study and it is not under a copyright more restrictive than CC-BY, please include a copy, in both the original language and English, as Supporting Information.

- Please further explain how "individuals with a highly confident personality" were identified.

- Please provide additional details regarding participant consent. In the ethics statement in the Methods and online submission information, please ensure that you have specified (1) whether consent was informed and (2) what type you obtained (for instance, written or verbal, and if verbal, how it was documented and witnessed).

4. In your Data Availability statement, you have not specified where the minimal data set underlying the results described in your manuscript can be found. PLOS defines a study's minimal data set as the underlying data used to reach the conclusions drawn in the manuscript and any additional data required to replicate the reported study findings in their entirety. All PLOS journals require that the minimal data set be made fully available. For more information about our data policy, please see http://journals.plos.org/plosone/s/data-availability.

Upon re-submitting your revised manuscript, please upload your study’s minimal underlying data set as either Supporting Information files or to a stable, public repository and include the relevant URLs, DOIs, or accession numbers within your revised cover letter. For a list of acceptable repositories, please see http://journals.plos.org/plosone/s/data-availability#loc-recommended-repositories. Any potentially identifying patient information must be fully anonymized.

Important: If there are ethical or legal restrictions to sharing your data publicly, please explain these restrictions in detail. Please see our guidelines for more information on what we consider unacceptable restrictions to publicly sharing data: http://journals.plos.org/plosone/s/data-availability#loc-unacceptable-data-access-restrictions. Note that it is not acceptable for the authors to be the sole named individuals responsible for ensuring data access.

We will update your Data Availability statement to reflect the information you provide in your cover letter.

5. PLOS requires an ORCID iD for the corresponding author in Editorial Manager on papers submitted after December 6th, 2016. Please ensure that you have an ORCID iD and that it is validated in Editorial Manager. To do this, go to ‘Update my Information’ (in the upper left-hand corner of the main menu), and click on the Fetch/Validate link next to the ORCID field. This will take you to the ORCID site and allow you to create a new iD or authenticate a pre-existing iD in Editorial Manager. Please see the following video for instructions on linking an ORCID iD to your Editorial Manager account: https://www.youtube.com/watch?v=_xcclfuvtxQ

6. Your ethics statement must appear in the Methods section of your manuscript. If your ethics statement is written in any section besides the Methods, please move it to the Methods section and delete it from any other section. Please also ensure that your ethics statement is included in your manuscript, as the ethics section of your online submission will not be published alongside your manuscript.

7. Please include captions for your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly. Please see our Supporting Information guidelines for more information: http://journals.plos.org/plosone/s/supporting-information.

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Partly

Reviewer #3: Yes

Reviewer #4: Partly

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: Yes

Reviewer #4: No

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: No

Reviewer #4: No

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The work aimed to determine the factors associated with amphetamine use among the hill tribe youths by a cross-sectional among 710 Akha and Lahu youths.

A. More clarification on the accuracy of gathering information on MA use is needed. Validity of instrument?

B. Provide reason of collecting data on violence during 0-5 years from parents.

Reviewer #2: The authors survey 2 population (as in sampling method) but presented in all which is inappropriate. Akha and Lahu are different ethnic group, thus cannot combine in analysis (could be compared).

Methodology such as sampling, sample size determination, Tool development are skeptical.

It seems that the findings are not significant related to Akha and Lahu culture specifically (it could be found in any youth in Thailand and other countries)

Reviewer #3: Comments from reviewers for the paper entitled “Associations of childhood experiences and methamphetamine use among Akha and Lahu hill tribe youths in northern Thailand: A cross-sectional study”

Abstract:

Should rewrite the result part more shortly as the authors wrote the result of the multivariate analysis quite details. Recommendation should be added by addressing the physical assault.

Introduction

Please add the prevalence of MA use in the Chiang Rai province, especially among this hill tribe.

The two sentences after references [14] should be combined into one sentence as the sentence is too short.

Please explain the term of childhood experiences. Please also add some references related to childhood experiences and MA use.

Methods

Authors put the heading Study population, eligible, Inclusion and exclusion criteria then study sample, which are confusing. Please put only Study sample with inclusion and exclusion criteria. Then the authors could describe about sampling, how the authors did randomly sampling, please describe more detail which method of randomly sapling used? Especially authors mentioned 496 people from 10 Akha villages and 518 people from 10 Lahu villages, was it random sampling or opportunistic

For sample size, please add the reference of p=0.27.

Researchers developed the Instruments based on the previous instruments or not, if yes, please give the references such as instruments related to chilhood experiences. This is interesting that the authors got the information from parents which had recall bias, how long that the authors asked back in the childhood experiences. Did the authors also asked the children themselves, to cross-check the information of childhood experiences. Please give the references related to the Instruments of history of being assaulted, history of school expulsion, assault by family members, especially assault by peers, did the parents knew about these issues.

Please also add the references of the questions related to knowledge and attitude toward MA use.

For the instrument, please specific which information that collected from parents and which information collected from children? As I am wondering that the authors collected the socio0denograhic of parents from themselves or collected from children. As the authors mentioned only that they collected childhood information from parents.

Please indicate IOC value and Cronbach’s alpha of 0.78 of which questions.

Pilot test should be conducted at least 30 participants, but the authors conducted pilot text only with 20, especially the authors had different target group Akha and other hill tribes, they should have at least 30 for each tribe.

Data Collection

Please specify which method of randomly selected the villages such as the simple, systematic and tec..

How select the participants from each village as the authors mentioned “496 people from 10 Akha villages and 518 people from 10 Lahu villages” Did the authors used PPS. Then how the authors did selected the participants from each selected village? Please specify the specific method of random sampling. Which methods that the authors interviewed the participants? How did you ensured the participants with low or not literacy? There were 71 participants had no education, how the participants answered to the questionnaire. What is the response rate?

Ethical

Please indicate the ethical approval Number, and how did the authors get the consent form from both parents and children.

Statistical Analysis

Please describe more about the multivariate analysis such as multiple logistic regression, which methods used, and which variables were enetred into the final model. Need to describe your statistical modeling techniques in much more detail.

Result

Table 2. History of family members’ exposure to drugs and alcohol

Please change to be Ever had or having as the authors included the past and currently.

Table 5: Participants’ behaviors and personality

Used MA at least once should be changed to be “Ever used MA at least once” and this should be included all variables as Ever used included past and currently.

Please indicate which variables entered in the model and the good fitness model. Please present the OR and 95%CI in the result for the variables significantly associated wit MA use. The authors showed in the table 6, but they did not described in the text.

Table 6 is too long, the authors could put in the appendix. The authors could briefly describe which variables were entered into the final model and which p valued in the univariate analysis, then the authors used which method for multivariate analysis such as backward elimination and presented only the final model that were significantly associated with MA use.

Discussion

This part is too short and please expand the discussion according to the variables were significantly associated wih MA use such as friends drinking related to MA? How/ Why? Had been physical assaulted by family member during childhood while aged 0-5 years and 6-14 years? How this related to MA? Are there any participants have been assault both during the 2 occasions. Please add more discussions and references to support for the factors associated with MA use.

Recomemndation should be revised according to the findings such as prevention of physical assaulted by family member during childhood. Please give more specific recomemndations.

Grammar - I would recommend reading through the manuscript purely to identify grammatical errors and awkward phrasing.

Reviewer #4: General comments:

This paper addressed an important topic and one of special relevance in Thailand where the methamphetamine (MA) epidemic has a profound impact on communities, especially in the north of the country. The paper presents results of a cross-sectional study evaluating the association of childhood experiences and the use of MA among hill tribe youth in northern Thailand. This is an important addition to the literature on the topic and the results can inform public health action and intervention in the area. The paper is mostly descriptive and the statistical methods could be explained in more detail. The paper could benefit from careful editing both for language and for clarity and minimizing logical repetitions.

Specific comments:

1. The abstract methods section could be edited and shortened to avoid repetitions of the phrase “…greater risk of MA use than those who did not…”

2. In the abstract, conclusions: the last sentence and intervention for “male youth” need to be better explained (I suppose as a target population)

3. Inclusion and exclusion: seems like the only criteria was age and the affiliation with the tribes, and understanding of Thai. And it will be helpful to note early on the population included youth who live in the tribal villages in the north of the country.

4. Sample size calculation: for a comparison of two independent proportions, in addition to a proportion for the one reference group a difference in proportion and the power level are needed to complete the calculations. Please add the necessary details. Actually, reading further, the analysis does not compare the two samples at all – rather, it is the association with MA use. So, the sample size need to reflect this!

5. Research instrument section: Survey questions in Part 3 on childhood abuse in ages 0-5 refer also to abuse by family members, yet it is noted that this part was filled in by parents?? Why would this be done? Also for those that are >18?

6. Piloting the questionnaire: were modification done between repeated cycles of the pilot? And what data was used for the reliability assessment?

7. Sample: after the 10 villages were randomly selected – how were the individual sampled? Were all youth in each village approached? Also more than one youth per household? In which case the analysis need to take this into account.

8. Results: what wasa the response rate? And what were reasons for non-participation?

9. Table 1: may be interesting to add two columns comparing the two sample, in addition to the total. Also, factors that were mostly missing such as income could be deleted from the tables

10. Tables 2-5 : can some of this information be presented in graphical form? Some items, for example “social behavior: yes/no” are hard to interpret; similarly items such as “accident” , “hospitalization” etc. are all these factors relevant? Also check the yes/no frequencies for question on parents support.

11. Table 6: to reduce length, possibly delete variables with p-value >0.2 or 0.3. also , some factors with small cells could be combined e.g. friends who use glue/heroin etc

12. How was the MV model developed? The initial model (all variables presented in table 6 presumably) have a mixture of socio-demographic characteristic, exposures and self substance use, other risk factors including childhood abuse but also type/circumstance of MA use. A more careful consideration of what is relevant to include in the model may be useful. In addition, How was the final MV model determined? Stepwise procedure? Showing only those factors that were significant (wrong approach)?

13. Was tribe a modifying factor for some covariates? The N may be large enough to allow some more refined analysis

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: Karl Peltzer

Reviewer #2: No

Reviewer #3: No

Reviewer #4: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files to be viewed.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email us at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2020 Jun 18;15(6):e0234923. doi: 10.1371/journal.pone.0234923.r002

Author response to Decision Letter 0


13 Apr 2020

PONE-D-20-01893

Associations of childhood experiences and methamphetamine use among Akha and Lahu hill tribe youths in northern Thailand: A cross-sectional study

PLOS ONE

Dear Dr. Apidechkul,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

We would appreciate receiving your revised manuscript by Apr 27 2020 11:59PM. When you are ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter.

To enhance the reproducibility of your results, we recommend that if applicable you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). This letter should be uploaded as separate file and labeled 'Response to Reviewers'.

• A marked-up copy of your manuscript that highlights changes made to the original version. This file should be uploaded as separate file and labeled 'Revised Manuscript with Track Changes'.

• An unmarked version of your revised paper without tracked changes. This file should be uploaded as separate file and labeled 'Manuscript'.

Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.

We look forward to receiving your revised manuscript.

Kind regards,

Siyan Yi, MD, MHSc, PhD

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements:

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at http://www.plosone.org/attachments/PLOSOne_formatting_sample_main_body.pdf and http://www.plosone.org/attachments/PLOSOne_formatting_sample_title_authors_affiliations.pdf

: The links provided are not working, however I have checked and improved according to the journal styles.

2. We suggest you thoroughly copyedit your manuscript for language usage, spelling, and grammar. If you do not know anyone who can help you do this, you may wish to consider employing a professional scientific editing service.

Whilst you may use any professional scientific editing service of your choice, PLOS has partnered with both American Journal Experts (AJE) and Editage to provide discounted services to PLOS authors. Both organizations have experience helping authors meet PLOS guidelines and can provide language editing, translation, manuscript formatting, and figure formatting to ensure your manuscript meets our submission guidelines. To take advantage of our partnership with AJE, visit the AJE website (http://learn.aje.com/plos/) for a 15% discount off AJE services. To take advantage of our partnership with Editage, visit the Editage website (www.editage.com) and enter referral code PLOSEDIT for a 15% discount off Editage services. If the PLOS editorial team finds any language issues in text that either AJE or Editage has edited, the service provider will re-edit the text for free.

Upon resubmission, please provide the following:

• The name of the colleague or the details of the professional service that edited your manuscript

• A copy of your manuscript showing your changes by either highlighting them or using track changes (uploaded as a *supporting information* file)

• A clean copy of the edited manuscript (uploaded as the new *manuscript* file)

: It has been done and improved by AJE, with verification code: 6EAB-88FC-7B3F-EF75-D4F1 .

: Certification attached.

3. Please address the following:

- Please include additional information regarding the survey or questionnaire used in the study and ensure that you have provided sufficient details that others could replicate the analyses. For instance, if you developed a questionnaire as part of this study and it is not under a copyright more restrictive than CC-BY, please include a copy, in both the original language and English, as Supporting Information.

- Please further explain how "individuals with a highly confident personality" were identified.

: Improved

- Please provide additional details regarding participant consent. In the ethics statement in the Methods and online submission information, please ensure that you have specified (1) whether consent was informed and (2) what type you obtained (for instance, written or verbal, and if verbal, how it was documented and witnessed).

: Improved

4. In your Data Availability statement, you have not specified where the minimal data set underlying the results described in your manuscript can be found. PLOS defines a study's minimal data set as the underlying data used to reach the conclusions drawn in the manuscript and any additional data required to replicate the reported study findings in their entirety. All PLOS journals require that the minimal data set be made fully available. For more information about our data policy, please see http://journals.plos.org/plosone/s/data-availability.

Upon re-submitting your revised manuscript, please upload your study’s minimal underlying data set as either Supporting Information files or to a stable, public repository and include the relevant URLs, DOIs, or accession numbers within your revised cover letter. For a list of acceptable repositories, please see http://journals.plos.org/plosone/s/data-availability#loc-recommended-repositories. Any potentially identifying patient information must be fully anonymized.

Important: If there are ethical or legal restrictions to sharing your data publicly, please explain these restrictions in detail. Please see our guidelines for more information on what we consider unacceptable restrictions to publicly sharing data: http://journals.plos.org/plosone/s/data-availability#loc-unacceptable-data-access-restrictions. Note that it is not acceptable for the authors to be the sole named individuals responsible for ensuring data access.

We will update your Data Availability statement to reflect the information you provide in your cover letter.

: Data has been uploaded.

5. PLOS requires an ORCID iD for the corresponding author in Editorial Manager on papers submitted after December 6th, 2016. Please ensure that you have an ORCID iD and that it is validated in Editorial Manager. To do this, go to ‘Update my Information’ (in the upper left-hand corner of the main menu), and click on the Fetch/Validate link next to the ORCID field. This will take you to the ORCID site and allow you to create a new iD or authenticate a pre-existing iD in Editorial Manager. Please see the following video for instructions on linking an ORCID iD to your Editorial Manager account: https://www.youtube.com/watch?v=_xcclfuvtxQ

: 0000-0001-8301-2055

6. Your ethics statement must appear in the Methods section of your manuscript. If your ethics statement is written in any section besides the Methods, please move it to the Methods section and delete it from any other section. Please also ensure that your ethics statement is included in your manuscript, as the ethics section of your online submission will not be published alongside your manuscript.

: Improved

7. Please include captions for your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly. Please see our Supporting Information guidelines for more information: http://journals.plos.org/plosone/s/supporting-information.

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Partly

Reviewer #3: Yes

Reviewer #4: Partly

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: Yes

Reviewer #4: No

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: No

Reviewer #4: No

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: Yes

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The work aimed to determine the factors associated with amphetamine use among the hill tribe youths by a cross-sectional among 710 Akha and Lahu youths.

A. More clarification on the accuracy of gathering information on MA use is needed. Validity of instrument?

: Improved in section of “method”

B. Provide reason of collecting data on violence during 0-5 years from parents.

: Improved, thank you for the comment.

Reviewer #2: The authors survey 2 population (as in sampling method) but presented in all which is inappropriate. Akha and Lahu are different ethnic group, thus cannot combine in analysis (could be compared).

Methodology such as sampling, sample size determination, Tool development are skeptical.

It seems that the findings are not significant related to Akha and Lahu culture specifically (it could be found in any youth in Thailand and other countries)

: Thank you for the comment, I (Dr.Tawatchai Apidechkul) as the principle investigator have long experience in working with the hill tribe in Thailand for more than 15 years. I really known that the hill tribes have different cultures, some aspect very big different, but some aspect is not too big. However, understanding in practice for MA use, I feel that it is not too much relevant to the tribe cultures but rather in parenting styles. The original idea for doing this project was from our observation on the date we visited the village, we found that some youths have started in use of MA while the other did not. This scenario was similar all tribes. But the reason to do for two tribes, because of research budget and also other components such as the feasibility to test the research hypothesis. With the help of WHO-Thailand staff and also the staff of Harvard Medical School who are my advisor. Then the research was completed and the findings come out.

We had done a small project before doing this study, please see deatil: BMC Public Health, 2019. DOI: 10.1186/s12889-019-7226-y

Reviewer #3: Comments from reviewers for the paper entitled “Associations of childhood experiences and methamphetamine use among Akha and Lahu hill tribe youths in northern Thailand: A cross-sectional study”

Abstract:

Should rewrite the result part more shortly as the authors wrote the result of the multivariate analysis quite details. Recommendation should be added by addressing the physical assault.

: Thank you very much for the comment. It is improved.

Introduction

Please add the prevalence of MA use in the Chiang Rai province, especially among this hill tribe.

: Thank you for the comment. I have tries so many times to seek the Thai and English information on the prevalence of MA use among people in Chiang Rai and also in the hill tribe, unfortunately , there is no information available. This was the information that we have had investigated before, during the study including in the period of writing up our manuscript, but no scientific or event the government’s report on the situation of the MA use among the hill tribe people.

The two sentences after references [14] should be combined into one sentence as the sentence is too short.

: Improved.

Please explain the term of childhood experiences. Please also add some references related to childhood experiences and MA use.

:Thank you for the comment. Based on our study, we just interest in detecting the association of individuals’ experience and MA use in later of their life among the hill tribe youths who are living in poor education and economic status.

UNICEF [United Nation International Children’s Emergency Fund. Childhood under threat : The state of the world’s children 2005. Available from: https://www.unicef.org/sowc05/english/childhooddefined.html ] defines the childhood as the time of children to be in school and at play, to grow strong and confident with the love and encouragement of their family and an extended community of caring adults. Therefore the childhood experience is the experience of children during their childhood period which could be positive and negative impact on their later life.

Since, the purpose of the study and also the design of the study were not focused on detection the association of neither negative or positive experience during childhood, so called “adverse Childhood experience (ACEs)” [Centers for Disease Control and Prevention (CDC). Violence prevention: adverse childhood experience (ACEs). Available from: https://www.cdc.gov/violenceprevention/childabuseandneglect/acestudy/index.html] and MA use, but we did a cross-sectional by assessing many exposures (including childhood experience) and MA use, then we avoid to use the word of “Adverse childhood experience” in the study.

Therefore, with the different conditions of the child experience (which is one of the exposures) and ACEs, then we decide to not put the ACEs into the paper, to avoid the confusion of readers. We very hope you understand us.

Methods

Authors put the heading Study population, eligible, Inclusion and exclusion criteria then study sample, which are confusing. Please put only Study sample with inclusion and exclusion criteria. Then the authors could describe about sampling, how the authors did randomly sampling, please describe more detail which method of randomly sapling used? Especially authors mentioned 496 people from 10 Akha villages and 518 people from 10 Lahu villages, was it random sampling or opportunistic

For sample size, please add the reference of p=0.27.

: It is referred to the reference no. 26 which is presented from the beginning. [Toeam A, Lapvongwatana P, Chansatitporn N, Chamroonsawasdi K. Predictive Factors of Amphetamine Use Among Youths in a Congested Community. Thai Red Cross Nursing Journal. 2016; 9(2): 88-103]

Researchers developed the Instruments based on the previous instruments or not, if yes, please give the references such as instruments related to childhood experiences. This is interesting that the authors got the information from parents which had recall bias, how long that the authors asked back in the childhood experiences. Did the authors also asked the children themselves, to cross-check the information of childhood experiences. Please give the references related to the Instruments of history of being assaulted, history of school expulsion, assault by family members, especially assault by peers, did the parents knew about these issues.

Please also add the references of the questions related to knowledge and attitude toward MA use.

: We had done a qualitative approach in understanding the MA use among these two population [Chomchoei C, Apidechkul T, Wongnuch P, Tamorapark R, Upala P, Nongkhai MP. Perceived factors influemcing the initiation of methamphetamine use among Akha and Lahu youths: a qualitative approach. BMC Public Health. 2019; 19: 847: DOI: 10.1186/s12889-019-7226-y.] before doing this project. We used the information from our qualitative phase to develop the tool especially the questionnaire in this quantitative phase.

: The questions related to history of being assaulted, history of school expulsion, assault by family members, especially assault by peers were also obtained from our own experience in doing research in these populations, literature review, and also consulted with expert. We did not sure that the parents known about the issues. Thank you very much for pointing out the great issue. We will discussion with team to find the great method in our next project to solve the problem in family and community levels.

: Along the steps of doing the project, parents were not informed anything regarding their child. And we did not do the cross-check information between parents and child information on 0-5 years because from our pilot phase, we did check the accuracy and found that their provided mostly similar between parents and child. Moreover, after the questionnaire reaching to researchers, no information could reflect to any individual’s information, then we did not do cross-check between parent and child during the study.

For the instrument, please specific which information that collected from parents and which information collected from children? As I am wondering that the authors collected the socio0denograhic of parents from themselves or collected from children. As the authors mentioned only that they collected childhood information from parents.

: Yes, only part three which was asking the child experience during aged 0-5 years, asked from their parents to improve the quality of the information due to the participants (children) were very young. In questionnaire part two which is asking on socioeconomic status was completed by participants (children). This is supported from the pilot period that most of the participants (children) have much more fluent in Thai (questionnaire was provided in Thai) than their parents and more understand the question.

Please indicate IOC value and Cronbach’s alpha of 0.78 of which questions.

Pilot test should be conducted at least 30 participants, but the authors conducted pilot text only with 20, especially the authors had different target group Akha and other hill tribes, they should have at least 30 for each tribe.

: Thank you for the comment. The IOC method is normally done by three experts in the field which is the common method. In pilot phase, we did for 10 participants because several reasons; 1) we have had some information from our previous study (reference no. 24); 2) to get the participants who were using Ma was very difficult; and 3) in the process of detecting the Cronbach’s alpha of 0.78, we did 3 times which is enough to improve the quality of the questions in section of KAP.

Data Collection

Please specify which method of randomly selected the villages such as the simple, systematic and tec..

: Improved

How select the participants from each village as the authors mentioned “496 people from 10 Akha villages and 518 people from 10 Lahu villages” Did the authors used PPS. Then how the authors did selected the participants from each selected village? Please specify the specific method of random sampling. Which methods that the authors interviewed the participants? How did you ensured the participants with low or not literacy? There were 71 participants had no education, how the participants answered to the questionnaire. What is the response rate?

: After making simple random method to get the selected list of the villages, people aged 15-24 who were living in the villages were invited to participate the study. The response rate was was 77.6% ( 385 of 496) in Akha, and 62.7% (325 of 518) in Lahu. This were acceptable for the survey design with some sensitive problem as MA. After getting the response, we had discussed on the response rates, but we have found that there were not different from our previous works among people in these two tribes.

: Those who responded on no-educated but still able to complete the questionnaire. This is also not surprise for us because from our previous studies and also our prior study in MA (reference No.24), we found that those who did not completely complete the 6th graded in primary school (grade 1-6), they would prefer to answer no education. For instance, a person finished in the 4th graded of primary school, with the answer of the questionnaire provided; no-education, primary education, secondary school, high school, vocational school, and university degree. They will answer in “no-educate”. The answer provided in the questionnaire is ordinal scales with one possible choice in each participant.

Ethical

Please indicate the ethical approval Number, and how did the authors get the consent form from both parents and children.

: Improved

Statistical Analysis

Please describe more about the multivariate analysis such as multiple logistic regression, which methods used, and which variables were enetred into the final model. Need to describe your statistical modeling techniques in much more detail.

:Improved

Result

Table 2. History of family members’ exposure to drugs and alcohol

Please change to be Ever had or having as the authors included the past and currently.

: Improved and thank you very much.

Table 5: Participants’ behaviors and personality

Used MA at least once should be changed to be “Ever used MA at least once” and this should be included all variables as Ever used included past and currently.

:Improved and thank you very much.

Please indicate which variables entered in the model and the good fitness model. Please present the OR and 95%CI in the result for the variables significantly associated wit MA use. The authors showed in the table 6, but they did not described in the text.

: Thank you very much for the comment. In the step of analysis, we started in consideration in each group of independent variables with dependent variable according to the conceptual framework. Along the analysis, pseudo R2 of Cox-Snell R2 and Nagelkerke R2 were used for the determination of fit of the model, and chi-square of the model was used for determination of the prediction of model to the dependent variable. In each step, those predicting variables which was not significant in the model, were excluded from the model because the statistic on fitting model and predicting the model showed not good to fit the model. In the best fit model in the last model (multivariate model) was used for presenting the most fit model in explaining the associations. And in the final step after 8 variables presented the associations, we have controlled the impact of “tribe, marital status, religion, education, occupation, and Thai ID card” in the final model to fit the associations.

: This is why we are not presenting every variables in the model, because we need to find the best fit model to explain the association according to both epidemiological and biostatistics concepts.

Table 6 is too long, the authors could put in the appendix. The authors could briefly describe which variables were entered into the final model and which p valued in the univariate analysis, then the authors used which method for multivariate analysis such as backward elimination and presented only the final model that were significantly associated with MA use.

: As this is the first pioneer study, we would like to show all variables that much related to the MA use. However, many variables, which found not too much relevant to the MA, have been deleted from the table. Since this is the fisrt pioneer study on MA among the two major hill tribe youths in Thailand, we very hope that many variables will be considered for the next research study.

: In the step of the analysis, we used “ENTER” mode which is allowed the researcher to consider the association in every step and we used the statistic on identifying in fitting the model. We did not concern only the association of the statistics but we also consider on the the association of the public health. Moreover, we used our original conceptual framework for doing the analysis.

: In the step of analysis, we started in consideration in each group of independent variables with dependent variable according to the conceptual framework. Along the analysis, pseudo R2 of Cox-Snell R2 and Nagelkerke R2 were used for the determination of fit of the model, and chi-square of the model was used for determination of the prediction of model to the dependent variable.

Discussion

This part is too short and please expand the discussion according to the variables were significantly associated wih MA use such as friends drinking related to MA? How/ Why? Had been physical assaulted by family member during childhood while aged 0-5 years and 6-14 years? How this related to MA? Are there any participants have been assault both during the 2 occasions. Please add more discussions and references to support for the factors associated with MA use.

: Thank you very much for the great question. There are 38 cases that presented had been physical assaulted in both period of life.

: We have extended our discussion to cover all aspects as suggested with numbers of references. Thank you very much for great comments here.

Recomemndation should be revised according to the findings such as prevention of physical assaulted by family member during childhood. Please give more specific recomemndations.

: Thank you for the comment, it’s improved.

Grammar - I would recommend reading through the manuscript purely to identify grammatical errors and awkward phrasing.

: Thank you very much, it is checked by the American Journal Experts with code no. 6EAB-88FC-7B3F-EF75-D4F1 .

Reviewer #4: General comments:

This paper addressed an important topic and one of special relevance in Thailand where the methamphetamine (MA) epidemic has a profound impact on communities, especially in the north of the country. The paper presents results of a cross-sectional study evaluating the association of childhood experiences and the use of MA among hill tribe youth in northern Thailand. This is an important addition to the literature on the topic and the results can inform public health action and intervention in the area. The paper is mostly descriptive and the statistical methods could be explained in more detail. The paper could benefit from careful editing both for language and for clarity and minimizing logical repetitions.

Specific comments:

1. The abstract methods section could be edited and shortened to avoid repetitions of the phrase “…greater risk of MA use than those who did not…”

: Thank you very much, it was improved.

2. In the abstract, conclusions: the last sentence and intervention for “male youth” need to be better explained (I suppose as a target population)

: Improved

3. Inclusion and exclusion: seems like the only criteria was age and the affiliation with the tribes, and understanding of Thai. And it will be helpful to note early on the population included youth who live in the tribal villages in the north of the country.

: Improved

4. Sample size calculation: for a comparison of two independent proportions, in addition to a proportion for the one reference group a difference in proportion and the power level are needed to complete the calculations. Please add the necessary details. Actually, reading further, the analysis does not compare the two samples at all – rather, it is the association with MA use. So, the sample size need to reflect this!

: Thank you for the comment. As we used a cross-sectional design which aimed to estimate the overall of the prevalence of MA use and to determine the factors associated with MA use. We did not aim to make a comparison from the earlier. Then, during the sample size calculation, it was looked as a whole sample size of the study sample. However, to much more sense in interpreting the finding, we divided into two proportional groups.

: Based on the concept of epidemiological studies in a cross-sectional design, two or more groups is not allowed. We measures both many exposures and outcome (MA use) in the same point of time according to its design.

5. Research instrument section: Survey questions in Part 3 on childhood abuse in ages 0-5 refer also to abuse by family members, yet it is noted that this part was filled in by parents?? Why would this be done? Also for those that are >18?

: Yes, this section (part 3) was asked on the experience during 0-5 years on the participants, but from our pilot phase we have found that the most abest way to gather the most accuracy information was from their parents due to the recall ability of participants (children). Therefore, we have asked these questions (part no3) from parents instead from children.

6. Piloting the questionnaire: were modification done between repeated cycles of the pilot? And what data was used for the reliability assessment?

: Yes, during the repeated cycles, many point had been improved such as the sentences, words, phrases used in the questionnaire, and also the order of the questions. Some words are very difficult and not familiar in the Akha and Lahu circumstance.

: The reliability test, we detected on KAP and present in overall Cronbach alpha of the questionnaire in the last cycle. Because in the first and second cycles, we focus on the feasible and understanding of the questions used, word used, paragraph used and the order of the questions.

7. Sample: after the 10 villages were randomly selected – how were the individual sampled? Were all youth in each village approached? Also more than one youth per household? In which case the analysis need to take this into account.

: Yes, all youths in the selected villages who met the criteria were invited to join the study. No conditions on the number of children in a household. After we got the list from village headman, we approach everyone.

8. Results: what wasa the response rate? And what were reasons for non-participation?

: Thank you for the comment, it was provide the response rate in section of the results.

9. Table 1: may be interesting to add two columns comparing the two sample, in addition to the total. Also, factors that were mostly missing such as income could be deleted from the tables

: Improved

10. Tables 2-5 : can some of this information be presented in graphical form? Some items, for example “social behavior: yes/no” are hard to interpret; similarly items such as “accident” , “hospitalization” etc. are all these factors relevant? Also check the yes/no frequencies for question on parents support.

: Thank you for the comments. Even this is a good idea, however, based on our raw data to present in form of graphic is very difficult.

: We so sorry, after getting back from AJE who checked and corrected the grammar for the paper, we did not checking again before submitting to the journal. In terms of “social behavior”, we mean socialized behavior. We have found that those who have much more activities including joining in parties were more at risk in use of MA. This is the original in putting the question into the questionnaire. Since this variable is a poor predictor in the logistic regression model, it was deleted from table no.6

11. Table 6: to reduce length, possibly delete variables with p-value >0.2 or 0.3. also , some factors with small cells could be combined e.g. friends who use glue/heroin etc

: Thank for the great comments. We have tried to deleted some variables that not too much related to the MA use such as p-value > 0.3 and did cell combination in some variables as suggestions which are related information in other tables such as table 1-4.

12. How was the MV model developed? The initial model (all variables presented in table 6 presumably) have a mixture of socio-demographic characteristic, exposures and self substance use, other risk factors including childhood abuse but also type/circumstance of MA use. A more careful consideration of what is relevant to include in the model may be useful. In addition, How was the final MV model determined? Stepwise procedure? Showing only those factors that were significant (wrong approach)?

: Thank you very much for the comment. Actually, we used “Enter” mode to extract the final model based on the conceptual framework in a cross-sectional method. Then to use “Backward” or “Forward” or “Stepwise” is not a good technique since we have to consider not just statistical significant but also public health significant (marginal significant) but it is needed to be included into the model. Under some condition, we have to consider on the size of the association (OR) and confident interval (CI), even the p-value is not shown the significance.

In the step of analysis, we started in consideration in each group of independent variables with dependent variable according to the conceptual framework. Along the analysis, pseudo R2 of Cox-Snell R2 and Nagelkerke R2 were used for the determination of fit of the model, and chi-square of the model was used for determination of the prediction of model to the dependent variable.

In the final step after 8 variables presented the associations, we have controlled the impact of “tribe, marital status, religion, education, occupation, and Thai ID card” in the final model to fit the associations.

13. Was tribe a modifying factor for some covariates? The N may be large enough to allow some more refined analysis

: Thank you very much for the suggestion. We have planned to do that, however, the analysis and results presented this article is based on our original purpose. We will do for analysis in different tribe, if any interest comes will be find a proper place for publication.

Thank you very much!

TK

Attachment

Submitted filename: Response to reviewers.docx

Decision Letter 1

Siyan Yi

7 May 2020

PONE-D-20-01893R1

Associations of childhood experiences and methamphetamine use among Akha and Lahu hill tribe youths in northern Thailand: A cross-sectional study

PLOS ONE

Dear Dr. Apidechkul,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

We would appreciate receiving your revised manuscript by Jun 21 2020 11:59PM. When you are ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter.

To enhance the reproducibility of your results, we recommend that if applicable you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). This letter should be uploaded as separate file and labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. This file should be uploaded as separate file and labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. This file should be uploaded as separate file and labeled 'Manuscript'.

Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.

We look forward to receiving your revised manuscript.

Kind regards,

Siyan Yi, MD, MHSc, PhD

Academic Editor

PLOS ONE

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

Reviewer #4: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: No

Reviewer #4: Partly

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: No

Reviewer #4: No

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #2: No

Reviewer #4: No

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: Yes

Reviewer #4: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: Although the author respond to comments, it is unclear.

Sampling method was straified cluster sampling, thus sample size calculation needs adjustment for design effect.

Reliability process is unusal (three rounds with the same 20 samples and calulated alpha from last round). Recall bias appeared. Alpha should be presented for individual section rather than overall.

Table 2-5 should be compare between two hill-tribes.

Although the MA lifetime prevalence is 3 times higher than general population of Thailand in 2019, it should be dicussed why it is.

The specific culture of these hill-tribes affected to MA use still need to clarify.

Reviewer #4: The authors were responsive to comments and the paper is now improved and has greater clarity overall. However, not all the relevant responses that are given in the letter to the editor are included in the paper. I have a few remaining comments:

Specific comments:

1. In the abstract, conclusions: the last sentence and intervention for “male youth” need to be better explained (I suppose as a target population) – this sentence is still not well phrased. is the intention to say: …interventions that lowers risk of MA use by addressing family relationship, male youth risk behaviors….etc….?

2. Sample size calculation: still need clearer description of what was done under what assumption. if the calculations were to estimate the proportion of MA use, then a single sample with confidence interval widths could be used. if it is based on comparing two proportions (which is what is indicated), then, explain which groups are compared and if this is within each tribe group? - this may not be a critical point in the paper but if included, it should be clear and relevant to the analysis performed.

3. As more than one youth per household could participate, can the authors add the info on how many clusters with size>1 were included? as the analysis does not take this clustering into account at a minimum, a note referring to potential biases in estimating the statistical significance (standard errors of estimates) should be included in methods and/or discussion. this is an important methodological issue.

4. Results: I do not find the reported “response rate” to the survey in the manuscript.

5. Table 1-5: the paper would benefit by creating tables 1-5 that contain more information including: a) the original n & 5 columns for overall frequencies and combining with it the univariate analysis that appears in table 6. then table 6 would just have the final multivariate table. this will be make it easier for the reader to capture the final model.

6. Description on how the MV model developed should be added to methods (it is in the response letter but not in the paper)

7. for goodness of fit for logistic mode – the c-statistics ( or area under the ROC) is preferable.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: Yes: Manop Kanato, Ph.D. Associate Professor, Department of Community Medicine, Khon Kaen University, Thailand. President of Administrative Committee of Substance abuse Academic Network, Office of the Narcotic Control Board of Thailand.

Reviewer #4: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files to be viewed.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email us at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2020 Jun 18;15(6):e0234923. doi: 10.1371/journal.pone.0234923.r004

Author response to Decision Letter 1


24 May 2020

Reviewer #2: Although the author respond to comments, it is unclear.

1.Sampling method was straified cluster sampling, thus sample size calculation needs adjustment for design effect.

: Thank you very much professor for such great comment. We have tried to calculate the sample size by putiing the effect size, however, it is still in around 700. Moreover, the from the CIs particularly in presentation the significant, there were presented with very narrow such as in sex; OR=4.75, 95%CI=2.27-9.95, and aged 21-24 years; OR=2.51, 95%CI=1.11-5.71.

: Moreover, this is a cross-sectional without any previous information particularly in the prevalence of MA use in this population, therefore, we have carefully discussed with two statisticians; one from Mahidol University and another one is my professor from Harvard School of Public Health, both them suggested that with the assumptions, it is good to use the samples obtained in the study.

: However, we will keep in mind this significant point from your comments for our next work. Thank you very much professor.

2.Reliability process is unusal (three rounds with the same 20 samples and calulated alpha from last round). Recall bias appeared. Alpha should be presented for individual section rather than overall.

: This is common while developing the quality of the tool. We can not calculate the the reliability in the first round because after finishing the first round, many points were changed and improved. It meat that we need to get the final and completed version to test and calculate for reliability score before use.

: Another very important point is this is the pioneer project on doing in the MA problem among the hill tribe who have limited in use Thai. Then, we had had very carefully obtained the information and also approached tham.

: I very hope that you understand us and thank you very much.

3. Table 2-5 should be compare between two hill-tribes.

: thank you for the comment, it’s revised and improved.

4. Although the MA lifetime prevalence is 3 times higher than general population of Thailand in 2019, it should be dicussed why it is. The specific culture of these hill-tribes affected to MA use still need to clarify.

: Thank you very much for the comment. It’s improved in page no.

Reviewer #4: The authors were responsive to comments and the paper is now improved and has greater clarity overall. However, not all the relevant responses that are given in the letter to the editor are included in the paper. I have a few remaining comments:

Specific comments:

1. In the abstract, conclusions: the last sentence and intervention for “male youth” need to be better explained (I suppose as a target population) – this sentence is still not well phrased. is the intention to say: …interventions that lowers risk of MA use by addressing family relationship, male youth risk behaviors….etc….?

: Thank you for comment, it’s improved.

2. Sample size calculation: still need clearer description of what was done under what assumption. if the calculations were to estimate the proportion of MA use, then a single sample with confidence interval widths could be used. if it is based on comparing two proportions (which is what is indicated), then, explain which groups are compared and if this is within each tribe group? - this may not be a critical point in the paper but if included, it should be clear and relevant to the analysis performed.

: Thank you so much for the valuable comment in this point. It has been revised an improved in section of sample size calculation.

: Since, there is no scientific data available on the prevalence of the MA use among the hill tribe population, then, the calculation for the sample size was based on the information (prevalence) from the study conducted in Thai youth who lived in the central of Bangkok which was conducted by Toeam, et al [26]. Moreover, based on the information of the number of population between the Akha and Lahu which was reported by the Hill tribe Welfare and Development Center [18], two tribes had similar size of the population living 243 Akah villages (approximately 60,000 population) and 216 Lahu villages (approximately 50,000 population).

3. As more than one youth per household could participate, can the authors add the info on how many clusters with size>1 were included? as the analysis does not take this clustering into account at a minimum, a note referring to potential biases in estimating the statistical significance (standard errors of estimates) should be included in methods and/or discussion. this is an important methodological issue.

: We have revised our raw data, and it was found that no household or family that presented more than one participant. We accept that we never though this issue before. We have learned this new point, thank you very much.

: However, we have put information in section of “step of data collection” to make clear the point.

4. Results: I do not find the reported “response rate” to the survey in the manuscript.

: We have responded to this point in our previous version regarding to the comment from one of reviewers. Please see the first sentences on the result section.

5. Table 1-5: the paper would benefit by creating tables 1-5 that contain more information including: a) the original n & 5 columns for overall frequencies and combining with it the univariate analysis that appears in table 6. then table 6 would just have the final multivariate table. this will be make it easier for the reader to capture the final model.

:Thank you very much for the comment. However, the previous reviewer suggested to put more statistics in table no.2-5 (Comment no.2). Therefore, we would like to maintain on univariate and multi variate analyses in same table (table 6). It’s also much more easier in explain the relationship between variables. I very hope that you understand us.

6. Description on how the MV model developed should be added to methods (it is in the response letter but not in the paper)

: Thank you very much for the comment. It’s improved in page no. 6

7. for goodness of fit for logistic mode – the c-statistics (or area under the ROC) is preferable.

: Thank you very much. This is one thing that I have learned thank you so much.

Thank you so much!

TK

Regards,

TK

Assistant Professor Dr.Tawatchai Apidechkul

Deputy Dean, School of Health Science, MFU

Director, Center of Excellence of the Hill tribe Health Research, WHO-CC

Former Hubert H Humphrey Fellow (2013-2014), Emory University

Global Health Delivery Intensive (Harvard School of Public Health)

Attachment

Submitted filename: Reviewers Comments and Responses.docx

Decision Letter 2

Siyan Yi

2 Jun 2020

PONE-D-20-01893R2

Associations of childhood experiences and methamphetamine use among Akha and Lahu hill tribe youths in northern Thailand: A cross-sectional study

PLOS ONE

Dear Dr. Apidechkul,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Jul 17 2020 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

We look forward to receiving your revised manuscript.

Kind regards,

Siyan Yi, MD, MHSc, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (if provided):

Thanks for your revisions. The manuscript is now much improved and almost ready for publication. However, since PLOS ONE does not allow you to proofread your manuscript after acceptance, I would like you to take this opportunity to do so. Here are some examples for your consideration:

1. I am not sure if ‘Thai-Myanmar-Laos Republic’ border is correct. If the ‘Republic’ is for Laos, the more commonly used is ‘Lao People's Democratic Republic’ or just ‘Laos.’

2. You may consider using ‘adverse childhood experiences’ which is widely used in the literature instead of ‘bad childhood experiences.’

3. Abstract:

- First sentence in Methods may be revised to avoid repeating the objective.

- Results: After controlling for…

- Since the analyses included both Akha and Lahu youth, repeating the expression ‘…among Akha and Lahu youth in northern Thailand’ brings more confusions than helps and unnecessarily increased the word count.

- I am not sure if ‘ORadj’is commonly used. May consider ‘adjusted odds ratio (AOR).

4. Methods:

- It would great if you could add a little bit more information on the inclusion criteria for both youth (participants) and parents. More information of the selection of the participants (youth and parents) is also required.

- Since this study was conducted among tribal populations, research instrument should also include information on the languages used for the questionnaire for each tribe, if translation (and back-translation) was performed, and average time required for the interview.

- ‘The questionnaires were conducted three (3) times in the same piloting samples…’ This is hard to understand: what does this mean? How many questionnaires were developed? If different questionnaires were developed for youth and parents, this should be clearly described.

- The flow of the information would be better if the sampling procedures (Steps of data collection) comes before ‘Research instruments.’

- ‘All questionnaires were properly destroyed after coding’ – what does this really mean? After data entry?

- The writing of ‘Statistical analysis’ can be improved by removing typos and grammatical errors. ‘Conceptual framework’ was mentioned without earlier discussion.

5. Please proofread the whole manuscript accordingly.

[Note: HTML markup is below. Please do not edit.]

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2020 Jun 18;15(6):e0234923. doi: 10.1371/journal.pone.0234923.r006

Author response to Decision Letter 2


3 Jun 2020

Additional Editor Comments (if provided):

Thanks for your revisions. The manuscript is now much improved and almost ready for publication. However, since PLOS ONE does not allow you to proofread your manuscript after acceptance, I would like you to take this opportunity to do so. Here are some examples for your consideration:

: Thank you so much!

1. I am not sure if ‘Thai-Myanmar-Laos Republic’ border is correct. If the ‘Republic’ is for Laos, the more commonly used is ‘Lao People's Democratic Republic’ or just ‘Laos.’

: Thank you so much for the correction in the point, it’s replaced by “Laos” in whole tex.

2. You may consider using ‘adverse childhood experiences’ which is widely used in the literature instead of ‘bad childhood experiences.’

: As we have responded to the point in previous version that in this study that the cross-sectional was used to explored on all factors relevant to MA use in late years of the Akha and Lahu youths. Having bad experience while very early ages were determined as one of factors in the model. Therefore, we have decided that if it is used the word of “adverse childhood experience” may not reflect the study concept.

: However, we concern a lot and have had long discussion in the point.

: Thank you very much for your concern, and now we are planning a new project to detect a particular of impact of “adverse childhood experience” among these population by a stronger study design.

: Thank you once again for your valuable suggestion.

3. Abstract:

- First sentence in Methods may be revised to avoid repeating the objective.

: Thank you so much, it’s improved.

- Results: After controlling for…

: Thank you, it’s improved

- Since the analyses included both Akha and Lahu youth, repeating the expression ‘…among Akha and Lahu youth in northern Thailand’ brings more confusions than helps and unnecessarily increased the word count.

: Thank you, we agree with you and it’s improved.

- I am not sure if ‘ORadj’is commonly used. May consider ‘adjusted odds ratio (AOR).

: Replaces all

4. Methods:

- It would great if you could add a little bit more information on the inclusion criteria for both youth (participants) and parents. More information of the selection of the participants (youth and parents) is also required.

: It’s improved. Detail of selection the participants is provided in the “Step of data collection”

- Since this study was conducted among tribal populations, research instrument should also include information on the languages used for the questionnaire for each tribe, if translation (and back-translation) was performed, and average time required for the interview.

: Thank you for great comment, it‘s improved. In the section of language, the questionnaire is provided in Thai because all of the participants including their parents are able to use Thai.

- ‘The questionnaires were conducted three (3) times in the same piloting samples…’ This is hard to understand: what does this mean? How many questionnaires were developed? If different questionnaires were developed for youth and parents, this should be clearly described.

: Since this is the pioneer of the project relevant to the MA use in the hill tribe, therefore, no standard or other questionnaire are available.

In this step (pilot), we had several purposes to do this such as sequencing of the questions, words or sentences used weather agiant culture or belief, or feel stigma or not, questions make free of sense to answer or not. Therefore, it’s needed to have many times to repeat for making sure the quality of the questionnaire is met.

: The questions for children, were tested among the youths and the questions for the parents were asked their parents accordingly.

: We developed only one set of questionnaires, with having six parts, presented detail in page. 4-5

: We very hope you understand our situation.

- The flow of the information would be better if the sampling procedures (Steps of data collection) comes before ‘Research instruments.’

: Thank you, it’s re-sequence accordinly

- ‘All questionnaires were properly destroyed after coding’ – what does this really mean? After data entry?

: It means that all filled questionnaire form (hard copy by participants and parents, there were destroyed after coding and putting into the computer by cutting it into a very small piece and burning with the university waste management processing. This reflects on the comments of the Ethical Consideration Board that to protect the release of any information to public which we has strictly followed the comments.

- The writing of ‘Statistical analysis’ can be improved by removing typos and grammatical errors. ‘Conceptual framework’ was mentioned without earlier discussion.

: Thank you so much, it’s improved.

5. Please proofread the whole manuscript accordingly.

: We all (authors) have carefully looked throughout the whole paper at least three rounds and many points have been improved. Thank you so much.

I have uploaded two files as supplements; questionnaire and data file of the study.

Thank you so much!

TK

Attachment

Submitted filename: Editor Comments and Response.docx

Decision Letter 3

Siyan Yi

5 Jun 2020

Associations of childhood experiences and methamphetamine use among Akha and Lahu hill tribe youths in northern Thailand: A cross-sectional study

PONE-D-20-01893R3

Dear Dr. Apidechkul,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Siyan Yi, MD, MHSc, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Acceptance letter

Siyan Yi

9 Jun 2020

PONE-D-20-01893R3

Associations of childhood experiences and methamphetamine use among Akha and Lahu hill tribe youths in northern Thailand: A cross-sectional study

Dear Dr. Apidechkul:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Siyan Yi

Academic Editor

PLOS ONE

Associated Data

    This section collects any data citations, data availability statements, or supplementary materials included in this article.

    Supplementary Materials

    S1 File. Questionnaire used in the study.

    (PDF)

    S2 File. Data file of the study.

    (XLSX)

    Attachment

    Submitted filename: Response to reviewers.docx

    Attachment

    Submitted filename: Reviewers Comments and Responses.docx

    Attachment

    Submitted filename: Editor Comments and Response.docx

    Data Availability Statement

    Data is fully available in supporting information file.


    Articles from PLoS ONE are provided here courtesy of PLOS

    RESOURCES