Prevalence and factors associated with illicit substance use among persons with Schizophrenia at a Tertiary Referral Hospital in Zambia

Kimberley R Kurehwatira; Emmanuel L Luwaya; Joreen P Povia; Chileleko Siakabanze; Salma M Baines; Emmanuel Yumba; Prince Mulambo; David N Masta; Nestorine N Ngongo; Natasha Chishala; Emmanuel O Riwo; Katongo H Mutengo; Hanzooma Hatwiko; Martin Chakulya; Lukundo Siame; Bislom C Mweene; Sepiso K Masenga

doi:10.1371/journal.pgph.0005024

. 2026 Jan 12;6(1):e0005024. doi: 10.1371/journal.pgph.0005024

Prevalence and factors associated with illicit substance use among persons with Schizophrenia at a Tertiary Referral Hospital in Zambia

Kimberley R Kurehwatira ^1,^2,^‡, Emmanuel L Luwaya ^1,^2,^‡, Joreen P Povia ³, Chileleko Siakabanze ², Salma M Baines ^1,², Emmanuel Yumba ^1,², Prince Mulambo ^1,², David N Masta ^1,², Nestorine N Ngongo ^1,², Natasha Chishala ^1,², Emmanuel O Riwo ^1,², Katongo H Mutengo ², Hanzooma Hatwiko ^1,², Martin Chakulya ^1,², Lukundo Siame ^1,², Bislom C Mweene ^1,², Sepiso K Masenga ^1,^2,^*

Editor: Yatan Pal Singh Balhara⁴

¹Department of Pathology, Mulungushi University, School of Medicine and Health Sciences, Livingstone, Zambia

²Department of Pathology, Livingstone Center for Prevention and Translational Science, Livingstone, Zambia

³Department of Health Economics, Livingstone Center for Prevention and Translational Science, Livingstone, Zambia

⁴AIIMS: All India Institute of Medical Sciences, INDIA

^✉

* E-mail: sepisomasenga@gmail.com, sepisomasenga@lcpts.org

The authors have declared that no competing interests exist.

‡ Share co-first authorship.

Roles

Kimberley R Kurehwatira: Conceptualization, Investigation, Methodology, Validation, Visualization, Writing – original draft, Writing – review & editing

Emmanuel L Luwaya: Validation, Visualization, Writing – original draft, Writing – review & editing

Joreen P Povia: Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing

Chileleko Siakabanze: Validation, Visualization, Writing – original draft, Writing – review & editing

Salma M Baines: Validation, Visualization, Writing – original draft, Writing – review & editing

Emmanuel Yumba: Validation, Visualization, Writing – original draft, Writing – review & editing

Prince Mulambo: Validation, Visualization, Writing – original draft, Writing – review & editing

David N Masta: Validation, Visualization, Writing – original draft, Writing – review & editing

Nestorine N Ngongo: Validation, Visualization, Writing – original draft, Writing – review & editing

Natasha Chishala: Validation, Visualization, Writing – original draft, Writing – review & editing

Emmanuel O Riwo: Validation, Visualization, Writing – original draft, Writing – review & editing

Katongo H Mutengo: Validation, Visualization, Writing – original draft, Writing – review & editing

Hanzooma Hatwiko: Validation, Visualization, Writing – original draft, Writing – review & editing

Martin Chakulya: Validation, Visualization, Writing – original draft, Writing – review & editing

Lukundo Siame: Validation, Visualization, Writing – original draft, Writing – review & editing

Bislom C Mweene: Validation, Visualization, Writing – original draft, Writing – review & editing

Sepiso K Masenga: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing

Yatan Pal Singh Balhara: Editor

PMCID: PMC12795356 PMID: 41525284

Abstract

Schizophrenia frequently involves comorbid substance use, exacerbating symptoms and reducing treatment efficacy yet no prior studies have examined this comorbidity locally. This study determined the prevalence and factors associated with illicit substance use among adults with schizophrenia at the Livingstone University Teaching Hospital (LUTH). A hospital-based single center cross-sectional study was conducted at LUTH from January to June 2023. A sample of 303 adults with schizophrenia were recruited via systematic random sampling. Data were collected from existing medical records which included documentation from structured interviews with validated tools (Alcohol, Smoking, and Substance Involvement Screening Test [ASSIST], Positive and Negative Syndrome Scale [PANSS]) conducted as part of routine clinical care. Sociodemographic, clinical, and substance use variables were analyzed using chi-square tests and multivariate logistic regression to identify factors associated with illicit substance use. The prevalence of illicit substance use was 31.1% (94/303). Alcohol use (AOR = 6.08, 95% CI: 3.14–11.78, p < 0.0001) and tobacco smoking (AOR = 4.80, 95% CI: 2.44–9.46, p < 0.0001) were strongly associated with illicit substance use. Factors associated with lower odds of illicit substance use included female sex (AOR = 0.27, 95% CI: 0.12–0.60, p = 0.001), marriage (AOR = 0.39, 95% CI: 0.19–0.79, p = 0.008), having both parents deceased (AOR = 0.29, 95% CI: 0.11–0.75, p = 0.011), and higher education (AOR = 0.44, 95% CI: 0.24–0.81, p = 0.009). Increased hospitalizations were associated with illicit substance use (AOR = 1.29, 95% CI: 1.01–1.65, p = 0.038). Integrated screening, gender-specific interventions, and socioeconomic support related to illicit substance use are urgently needed in Zambia’s resource-constrained setting.

Introduction

Schizophrenia, a debilitating psychiatric disorder affecting approximately 24 million people globally (WHO, 2022) [1], is characterized by profound disruptions in cognition, emotion, and behaviour [2]. In sub-Saharan Africa (SSA), schizophrenia is compounded by systemic challenges such as poverty, stigma, and fragmented healthcare systems. Comorbid substance use, prevalent in 40–60% of schizophrenia cases globally [3], exacerbates disease burden, impairing treatment adherence and increasing relapse rates. In SSA, this comorbidity is particularly severe, with studies reporting substance use rates as high as 58–65% among persons with schizophrenia [3]. Zambia, a low-income country with a population of 22 million, faces acute mental health challenges: mental disorders account for 13% of the national disease burden, yet the country has only ten psychiatrists as reported by WHO in 2023 [4], a slight increase from five psychiatrists in 2017, and limited mental health funding [5]. The University Teaching Hospital (LUTH), Zambia’s largest referral center, struggles with high patient loads and resource constraints, making it a critical site for studying schizophrenia and substance use.

Substance use patterns are shaped by cultural, economic, and environmental factors [6–11]. The widespread use of kachasu (a cheap, a traditionally fermented, highly intoxicating, distilled alcoholic spirit), cannabis, and emerging synthetic drugs is normalized in many communities. Economic hardship affecting 52.4% of Zambians who live below the poverty line [12] and unemployment (13.1% nationally) drive maladaptive coping behaviours, including substance use. Traditional beliefs attributing mental illness to spiritual causes further delay biomedical care, pushing patients toward self-medication with substances [10]. Despite these challenges, no studies have systematically examined the prevalence or correlates of illicit substance use among persons with schizophrenia in Zambia. This gap impedes the development of culturally tailored interventions, perpetuating cycles of poor outcomes.

Zambia’s mental health system is strained: mental health receives <1% of the health budget, and community stigma forces many patients into isolation [12]. Illicit substance use among persons with schizophrenia at LUTH remains unstudied, yet it likely fuels high relapse rates and recurrent hospitalizations. The study determined the prevalence and factors associated with illicit substance use among adults with schizophrenia at the University Teaching Hospital (LUTH) in Zambia. We hypothesized that male sex, alcohol use, and tobacco smoking would be associated with higher odds of illicit substance use, while factors like higher education and being married would be associated with lower odds.

Methodology

Ethics statement

Ethical approval was obtained from the Mulungushi University School of Medicine and Health Sciences Research Ethics Committee (ethics reference number SMHS-MU1-2025-42) on 24 March 2025. Administrative permission was granted by LUTH management. All extracted data were anonymized to protect confidentiality. All data collected and analyzed were de-identified to ensure complete confidentiality. No information leading to identification of patients during and after analysis was abstracted and entered in the data collection form. Secondary data were used in this project. A written/verbal consent was not applicable and was therefore waived by the ethics committee.

Study design

This was a retrospective cross-sectional study. We used existing medical records from persons with schizophrenia at LUTH in Zambia.

Study setting

The research was conducted at the Psychiatry Department of LUTH, a tertiary referral hospital located in Livingstone, Zambia. The department systematically documents clinical features, substance use history, and treatment of persons diagnosed with schizophrenia.

Study population

Target population.

Adults (≥18 years) with schizophrenia in Livingstone.

Accessible population.

Persons with Schizophrenia seeking care at LUTH’s Psychiatry Department (between January 2021 and December 2024).

Actual study population

303 patients meeting inclusion criteria, representing 36.1% of screened records (303/840). All subtypes of schizophrenia (ICD-10: F20.0–F20.9) were included.

A post-hoc power analysis was conducted using G*Power 3.1 to evaluate the statistical power of our study design. This analysis revealed 99.8% power at α = 0.05 to detect the observed effect size (OR=6.79) for the primary variable of male sex. However, for rare outcomes such as suicidality, where only three cases were observed, the power was substantially lower at just 12% to detect meaningful associations. The power calculation for male sex specifically employed a two-proportion z-test for independent samples with a two-tailed design. This test compared proportions of 0.448 (substance use in males) and 0.107 (substance use in females), with sample sizes of 181 males and 122 females at the conventional alpha level of 0.05. These parameters confirmed robust power for our main sex-based comparison while highlighting limitations for analyzing infrequent outcomes.

Eligibility and recruitment

We reviewed medical records of persons diagnosed with schizophrenia who received care at LUTH between January 2021 and December 2024. The diagnosis of schizophrenia was made by a consultant psychiatrist according to ICD-10 criteria. Both inpatients and outpatients were included, regardless of their clinical remission status. Records were included if the patient was 18 years or older, had a confirmed psychiatrist-diagnosed schizophrenia (ICD-10 F20), and the medical record contained complete documentation of sociodemographic data and substance use history. A total of 303 patient records were included in the final analysis. Records were included if the patient had a confirmed diagnosis of schizophrenia and complete documentation of sociodemographic and substance use information. Records missing key variables were excluded.

Data collection

Data were collected through a structured file review process between 1^st April and 28 April 2025. Trained research assistants extracted relevant data from patients’ medical files into a REDCap database. No patient interviews were conducted. Information from structured clinical interviews (e.g., ASSIST, PANSS) had been previously conducted by clinic staff and documented in the records; this historical data was extracted for analysis. To ensure data quality, 10% of the records were subjected to dual review for accuracy and consistency, and performed an audit trail using RedCap audit logs to track all data entries and revisions. Additionally, records missing variables were excluded. Other quality measures included the training of personnel involved in data collection using mock records and piloting on records to refine variable definitions.

Assessment of clinical variables

Clinical variables were ascertained from the psychiatrist’s notes and assessment scales documented in the medical records. Hallucinations, delusions, disorganized speech, disorganized behavior, and negative symptoms were assessed and documented by the treating psychiatrist based on clinical evaluation and, where available, PANSS scores. Cognitive impairment was noted based on clinical observation and any documented cognitive assessments. Suicidality and self-harm were defined by documented reports of suicidal ideation, plans, or attempts, or acts of non-suicidal self-injury. Violent behavior was defined as documented episodes of physical aggression towards others or property.

Study variables

The primary outcome variable was current illicit substance use, defined as documented use of psychoactive substances (cannabis, cocaine, opioids, or others) within the past 12 months.

Independent variables included: Sociodemographic Variables (Age, Sex, Marital status, Educational level, Employment status, Residence, Parental status) and Clinical Variables (hallucinations and type, delusions and type, disorganized speech, disorganized behavior, negative symptoms, cognitive impairment, suicidality and self-harm, violent behavior, family history, tobacco smoking status, awareness of diagnosis, consultation with traditional healers, medication adherence, number of hospitalizations, hematological and biochemical parameters).

Data analysis

Data were exported from REDCap into Microsoft Excel 2013 for cleaning and coding, then analyzed using StatCrunch (StatCrunch, LLC, Pearson’s web-based statistical software). Descriptive statistics summarized categorical variables (frequencies and percentages) and continuous variables (medians and interquartile ranges [IQR]). Normality was assessed using the Shapiro-Wilk test. Associations between categorical variables were evaluated using the Chi-square test, while differences between continuous variables were assessed using the Wilcoxon rank-sum test. Univariable and multivariable logistic regression analyses were performed to identify factors associated with current illicit substance use. Adjusted odds ratios (AORs) with 95% confidence intervals (CIs) were reported. A p-value of < 0.05 was considered statistically significant.

Variable selection for multivariable logistic regression required balancing statistical rigor with clinical relevance and practical constraints. Key steps included an initial screening phase using liberal p-values (e.g., < 0.20 - 0.25), followed by final variable inclusion based on stricter statistical significance (p < 0.05). Crucially, clinically important variables were mandatorily considered for inclusion regardless of their statistical p-value. Potential multicollinearity among variables was assessed using the Variance Inflation Factor (VIF < 10), absolute correlation coefficients (|r| < 0.8), and condition index (< 30). Sample size sufficiency was ensured, ideally targeting a minimum of 10–15 + events per variable. Various selection methods (e.g., Forward, Backward, Stepwise, Best Subset) were employed, guided by criteria such as p-values or information criteria like the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC). The final model was derived using backward elimination, and variables significant in bivariate analysis but not included in the final model (e.g., negative symptoms, awareness of diagnosis) were excluded because they did not meet the significance threshold (p < 0.05) for retention during the stepwise selection process or did not improve the model fit as per AIC.

Model comparison and refinement utilized indices including AIC, BIC, the Area Under the receiver operating characteristic Curve (AUC), and goodness-of-fit tests such as the Hosmer-Lemeshow test. Practical considerations, such as data availability, cost, and interpretability, were integrated alongside the evaluation of potential interaction terms. Thorough validation, encompassing both internal and external approaches, was deemed critical for developing a robust, generalizable, and clinically useful model.

This comprehensive framework guided our approach in the schizophrenia study. Specifically, we applied backward elimination (starting with all candidate variables and sequentially removing those with p > 0.05), compared competing models based on AIC values, and assessed goodness-of-fit using the Hosmer-Lemeshow test. This process resulted in a final, robust 7-variable model with optimized performance.

We used the Strengthening the Reporting of Observational Studies in Epidemiology to guide the writing (S1 Strobe).

Results

From a total of 1000 files available for abstraction, 840 medical records were reviewed, 303 records met the inclusion criteria and were included in the analysis. The remaining 538 records were excluded due to incomplete information, such as missing details on age, sex, residence, diagnosis or the outcome, Fig 1.

Characteristics of the study population

A total of 303 participants were enrolled in this study, with a median age of 31 years (IQR: 24–41), Table 1. The cohort comprised 59.7% males (n = 181) and 40.3% females (n = 122). Bivariate analyses revealed numerous significant associations with illicit substance use. Females exhibited substantially lower illicit substance use prevalence than males (10.7% vs. 44.8%, p < 0.0001). Married participants had significantly lower illicit substance use rates compared to unmarried individuals (17.3% vs. 43.2%, p < 0.0001). Those with both parents deceased showed reduced illicit substance use (18.0% vs. 34.9% in others, p = 0.011), while participants with negative symptoms had lower rates than those without (19.2% vs. 33.9%, p = 0.038). Illicit substance use was strongly associated with alcohol use (60.2% vs. 13.7% in non-users, p < 0.0001), tobacco smoking (61.5% vs. 15.1% in non-smokers, p < 0.0001), and violent behavior (67.0% vs. 38.5% in non-violent participants, p < 0.0001). Medication non-adherence was linked to higher illicit substance use (46.0% vs. 16.4% in adherent individuals, p < 0.0001), while awareness of one’s condition was associated with lower illicit substance use (21.2% vs. 39.5% in unaware individuals, p = 0.0006). The illciti substance use group had significantly more hospitalizations (median = 3, IQR:2–4) than the non-use group (median = 2, IQR:1–3, p = 0.044), and younger age was associated with illcit substance use (p = 0.023). Participants with suicidal ideation (n = 3) all had illicit substance use (p = 0.029).

Table 1. Characteristics of the study populations.

Variable	Median (IQR) or Frequency (%)	No Illicit Substance Use % (n) [95% CI]	Yes Illicit Substance Use % (n) [95% CI]	P. value
Age (years)	31 (24,41)	68.9 (208)	31.1 (94)	0.023
Sex, n = 301
Male	59.7 (181)	55.3 (100) [47.7, 62.6]	44.8 (81) [37.4, 52.3]	<0.0001
Female	40.3 (122)	89.3 (109) [82.7, 94.2]	10.7 (13) [5.8, 17.3]
Marital Status, n = 301
Married	46.2 (139)	82.7 (115) [75.6, 88.5]	17.3 (24) [11.5, 24.4]
Not Married	53.8 (162)	56.8 (92) [48.9, 64.4]	43.2 (70) [35.6, 51.1]	<0.0001
Educated, n = 300
Primary	47.7 (143)	63.6 (91) [55.3, 71.4]	36.4 (52) [28.6, 44.7]	0.074
Secondary	46.7 (140)	71.4 (100) [63.3, 78.7]	28.6 (40) [21.3, 36.7]
Tertiary	5.7 (17)	88.2 (15) [63.6, 98.5]	11.8 (2) [1.5, 36.4]
Employment Status, n = 292
Unemployed	69.6 (204)	66.2 (135) [59.3, 72.6]	33.8 (69) [27.4, 40.7]	0.080
Employed	30.4 (88)	76.4 (68) [66.9, 84.8]	23.6 (21) [15.2, 33.1]
Residence, n = 297
Urban	82.8 (246)	68.7 (169) [62.6, 74.3]	31.3 (77) [25.7, 37.4]	0.587
Rural	17.17 (51)	72.6 (37) [58.3, 84.1]	27.4 (14) [15.9, 41.7]
Both Parents Alive, n = 296
No	58.8 (174)	70.7 (123) [63.4, 77.3]	29.3 (51) [22.7, 36.6]	0.431
Yes	41.2 (122)	66.4 (81) [57.3, 74.7]	33.6 (41) [25.3, 42.7]
Both Parents Deceased, n = 296
No	79.4 (235)	65.1 (153) [58.7, 71.1]	34.9 (82) [28.9, 41.3]	0.011
Yes	20.6 (61)	82.0 (50) [70.0, 90.6]	18.0 (11) [9.4, 30.0]
Hallucinations, n = 301
No	18.3 (55)	69.1 (38) [55.2, 80.9]	30.9 (17) [19.1, 44.8]	0.954
Yes	81.7 (246)	68.7 (169) [62.6, 74.3]	31.3 (77) [25.7, 37.4]
Delusions,
No	41.9 (127)	69.3 (88) [60.6, 77.1]	30.7 (39) [22.9, 39.4]	0.919
Yes	58.1 (176)	68.7 (121) [61.4, 75.4]	31.3 (55) [24.6, 38.6]
Disorganized Speech, n = 300
No	43.7 (131)	74.0 (97) [65.7, 81.2]	26.0 (34) [18.8, 34.3]	0.096
Yes	56.3 (169)	65.1 (110) [57.4, 72.2]	34.9 (59) [27.8, 42.6]
Disorganized Behaviour, n = 302
No	8.3 (25)	72.0 (18) [50.6, 87.9]	28.0 (7) [12.1, 49.4]	0.724
Yes	91.7 (277)	68.6 (190) [62.8, 74.0]	31.4 (87) [26.0, 37.2]
Negative Symptoms, n = 300
No	82.7 (248)	66.1 (164) [59.9, 71.9]	33.9 (84) [28.1, 40.1]	*0.038*
Yes	17.3 (52)	80.8 (42) [67.5, 90.4]	19.2 (10) [9.6, 32.5]
Cognitive Impairment, n = 300
No	39 (117)	75.2 (88) [66.4, 82.6]	24.8 (29) [17.4, 33.6]	0.062
Yes	61 (183)	65.0 (119) [57.6, 71.9]	35.0 (64) [28.1, 42.4]
Suicidal,
No	99.0 (300)	69.7 (209) [64.1, 74.9]	30.3 (91) [25.1, 35.9]	*0.029*
Yes	0.1 (3)	0.0 (0) [0.0, 70.8]	100.0 (3) [29.2, 100.0]
History of Self Harm, n = 302
No	93 (281)	68.7 (193) [63.0, 74.0]	31.3 (88) [26.0, 37.0]	0.793
Yes	7 (21)	71.4 (15) [47.8, 88.7]	28.6 (6) [11.3, 52.2]
Family History of Schizophrenia
No	97 (294)	68.7 (202) [63.1, 73.9]	31.3 (92) [26.1, 36.9]	0.725
Yes	3 (9)	77.8 (7) [40.0, 97.2]	22.2 (2) [2.8, 60.0]
Family History of Other Psychiatric Illness, n = 294
No	75.3 (225)	71.6 (161) [65.2, 77.4]	28.4 (64) [22.6, 34.8]	0.128
Yes	24.7 (74)	62.1 (46) [50.1, 73.0]	37.9 (28) [27.0, 49.9]
Alcohol Use
No	62.7 (190)	86.3 (164) [80.5, 90.9]	13.7 (26) [9.1, 19.5]	*<0.0001*
Yes	37.3 (113)	39.8 (45) [30.7, 49.5]	60.2 (68) [50.5, 69.3]
Violent Behaviour, n = 302
No	52.6 (159)	61.5 (128) [53.8, 68.9]	38.5 (80) [31.1, 46.2]	<0.0001
Yes	47.4 (143)	33.0 (31) [25.4, 41.3]	67.0 (96) [58.7, 74.6]
Tobacco Smoking, n = 302
No	65.6 (198)	84.9 (168) [79.1, 89.5]	15.1 (30) [10.5, 20.9]	<0.0001
Yes	34.4 (104)	38.5 (40) [29.0, 48.7]	61.5 (64) [51.3, 71.0]
Aware Of Condition, n = 299
No	54.2 (162)	60.5 (98) [52.5, 68.1]	39.5 (64) [31.9, 47.5]	*0.0006*
Yes	45.8 (137)	78.8 (108) [71.1, 85.3]	21.2 (29) [14.7, 28.9]
Consulted Traditional Healers, n = 241
No	83.0 (200)	68.0 (136) [61.1, 74.4]	32.0 (64) [25.6, 38.9]	0.514
Yes	17.0 (41)	73.2 (30) [57.1, 85.8]	26.8 (11) [14.2, 42.9]
Patient Adherent to Medication, n = 293
No	48.1 (141)	54.0 (76) [45.4, 62.4]	46.0 (65) [37.6, 54.6]	*<0.0001*
Yes	51.9 (152)	83.6 (127) [76.7, 89.1]	16.4 (25) [10.9, 23.3]
Number of hospitalizations	2 (2, 3)	2 (1, 3)	3 (2, 4)	0.044

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Assessment of collinearity between variables

Firstly, the correlation matrix performed showed no high correlations (>0.7) between variables, which is good for avoiding multicollinearity, Fig 2.

For a more precise assessment of collinearity, we calculated the Variance Inflation Factor (VIF) (S1 Table) for fitting a logistic regression model and performed the Hosmer-Lemeshow goodness-of-fit test. The Hosmer-Lemeshow test indicated a good model fit (p = 0.3794 > 0.05), meaning we fail to reject the null hypothesis of adequate fit, S2 Table. The model showed good discriminative ability with 83% accuracy, pseudo R² of 0.46, and reasonable precision/recall for both classes.

Factors associated with substance use in logistic regression

We performed a model comparison and cross-validation comparison for the best logistic regression model for the variables in the study. The backward elimination model performed best overall with the lowest AIC, though the Hosmer-Lemeshow test (Pseudo R-squared of 0.3863; AIC of 246.33 (lowest among all models) and Cross-validation accuracy of 75.93%) suggested poor calibration (p = 0.0196) that might be addressed with additional model refinements, S3 Table.

The analysis revealed several factors significantly associated with illicit substance use, both in the initial unadjusted models (OR) and after adjusting for other variables (AOR), Table 2. Sex demonstrated a strong protective effect. In the unadjusted model, the odds of substance use were significantly lower for females compared to males (OR = 0.14, 95% CI: 0.07-0.28, p < 0.0001). This association remained significant, though attenuated, in the adjusted model (AOR = 0.27, 95% CI: 0.12-0.60, p = 0.001). Similarly, being Married was associated with substantially lower odds of illcit substance use initially (OR = 0.27, 95% CI: 0.16-0.47, p < 0.0001), and this association persisted even after adjustment (AOR = 0.39, 95% CI: 0.19-0.79, p = 0.008).

Table 2. Logistic regression analysis for Substance use.

Variables	OR (95%CI)	p. value	AOR (95%CI)	p. value
Sex	0.14 (0.07,0.28)	<0.0001	0.27 (0.12, 0.60)	0.001
Married	0.27 (0.16,0.47)	<0.0001	0.39 (0.19, 0.79)	0.008
Both Parents Deceased	0.41 (0.20,0.83)	0.013	0.29 (0.11,0.75)	0.011
Educated	0.62 (0.40, 0.95)	0.029	0.44 (0.24, 0.81)	0.009
Alcohol Use	9.53 (5.44,16.67)	<0.0001	6.08 (3.14,11.78)	<0.0001
Smoking	8.96 (5.15,15.59)	<0.0001	4.80 (2.44,9.46)	<0.0001
Number of hospitalizations	1.16 (0.98,1.38)	0.076	1.29 (1.01,1.65)	0.038
Violent Behaviour	3.25 (1.94, 5.43)	<0.0001
Negative Symptoms	0.46 (0.22,0.97)	0.041
Aware of Condition	0.41 (0.25,0.69)	0.0008
Adherence to medication	0.23 (0.134,0.39)	<0.0001
Age	0.97 (0.95,0.99)	0.020

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The status of having Both Parents Deceased also emerged as associated with lower odds of illicit substance use. The unadjusted model showed lower odds (OR = 0.41, 95% CI: 0.20-0.83, p = 0.013), and interestingly, this association became stronger in the adjusted model (AOR = 0.29, 95% CI: 0.11-0.75, p = 0.011). Higher levels of being Educated were associated with moderately lower odds of illicit substance use in the unadjusted analysis (OR = 0.62, 95% CI: 0.40-0.95, p = 0.029). After adjustment, this association increased in magnitude and significance (AOR = 0.44, 95% CI: 0.24-0.81, p = 0.009).

Conversely, Alcohol Use was strongly associated with illicit substance use. Individuals using alcohol had dramatically higher odds of illicit substance use in the unadjusted model (OR = 9.53, 95% CI: 5.44-16.67, p < 0.0001). Although this association lessened somewhat in the adjusted model, it remained highly significant and strong (AOR = 6.08, 95% CI: 3.14-11.78, p < 0.0001). Tobacco smoking exhibited a similarly strong association. The unadjusted odds were very high (OR = 8.96, 95% CI: 5.15-15.59, p < 0.0001), and while reduced, the association remained large and highly significant after adjustment (AOR = 4.80, 95% CI: 2.44-9.46, p < 0.0001).

The Number of hospitalizations showed a trend towards being associated with illicit substance use in the unadjusted model but did not reach conventional statistical significance (OR = 1.16, 95% CI: 0.98-1.38, p = 0.076). However, after adjusting for other factors, a higher number of hospitalizations became a statistically significant variable associated with increased odds of illicit substance use (AOR = 1.29, 95% CI: 1.01-1.65, p = 0.038).

Several factors were significant in the unadjusted model but were not retained or reported in the final adjusted model presented. Exhibiting Violent Behaviour was associated with substantially higher odds of illicit substance use (OR = 3.25, 95% CI: 1.94-5.43, p < 0.0001). Higher levels of Negative Symptoms appeared to have an association with lower odds of illicit substance use (OR = 0.46, 95% CI: 0.22-0.97, p = 0.041). Being Aware of Condition was associated with significantly lower odds of illicit substance use (OR = 0.41, 95% CI: 0.25-0.69, p = 0.0008). Adherence to medication was associated with lower odds of illicit substance use in the unadjusted analysis (OR = 0.23, 95% CI: 0.134-0.39, p < 0.0001). Finally, increasing Age was associated with slightly lower odds of illicit substance use in the unadjusted model (OR = 0.97, 95% CI: 0.95-0.99, p = 0.020).

In summary, the variables most strongly associated with illicit substance use in the adjusted model were alcohol use and tobacco smoking. Variables associated with lower odds of illicit substance use in the adjusted model included being female, being married, having both parents deceased, and higher education. An increased number of hospitalizations was also associated with illicit substance use after adjustment. Factors like violent behaviour, negative symptoms, awareness of condition, medication adherence, and age were significant in the bivariate analysis but were not included in the final adjusted model (did not retain significance and did not meet the criteria for inclusion in the final model).

Discussion

The identification of alcohol use, tobacco smoking, and male sex as factors independently associated with illicit substance use in schizophrenia underscores critical intersections between behavioural, biological, and social factors in this population. These findings align with existing literature that positions illicit substance use as both a coping mechanism and a contributor to the complex psychopathology of schizophrenia. The substance use prevalence of 31.1% in our cohort is lower than SSA averages (58–65%) [13] but aligns with Nigerian (43%) [14] and Ethiopian (46.8%) [15] studies. This discrepancy may reflect Zambia’s strict substance criminalization or under detection in records. Crucially, alcohol and tobacco smoking were dominant correlates, mirroring global patterns where 60–80% of persons with schizophrenia use tobacco [16] and 30–50% misuse alcohol [17]. Neurobiological mechanisms such as nicotine’s transient amelioration of cognitive deficits [18,19] and socioeconomic drivers like kachasu affordability likely underpin this. Alcohol and tobacco may serve dual roles: temporarily alleviating symptoms such as anxiety or cognitive deficits while perpetuating cycles of addiction through neurobiological pathways [20,21]. The prominence of these substances highlights the need to address polysubstance use as a multifaceted challenge rather than isolated behaviors.

Factors associated with lower odds of illicit substance use in multivariable analysis

The identification of female sex, marriage, higher education, and parental loss as factors associated with lower odds of illicit substance use in adjusted models reveals nuanced socio-familial buffers against substance use. The robust association of female sex (AOR = 0.27) aligns with global epidemiological patterns [22,23] but contrasts with Jordanian data where male gender dominated risk profiles [24]. This underscores gender-specific social norms in Zambia, where cultural stigmatization may disproportionately deter illicit substance use among women. Marriage retained significance after adjustment (AOR = 0.39), suggesting spousal support may mitigate isolation-driven illicit substance use, though this effect is attenuated when illicit substance-related behaviours are entrenched. Unexpectedly, having both parents deceased was associated with lower odds of illicit substance use (AOR = 0.29), potentially reflecting early resilience-building or alternative kinship support, a finding warranting qualitative exploration [10,25].

The persistence of male sex as a factor associated with illicit substance use raises important questions about gender-specific vulnerabilities. A wide confidence interval for sex variable reflects limited female illicit substance users (n = 13), reducing precision. Despite this, the strong effect size (AOR > 5) and statistical significance (p = 0.003) support male gender as a key correlate. Biological differences, such as hormonal influences on dopamine regulation, may be linked to higher addiction rates. Sociocultural factors, including gendered norms around substance use and disparities in healthcare-seeking behaviour, likely further amplify this association [6,25]. This duality suggests that interventions must extend beyond clinical settings to address broader societal influences, particularly in communities where male illicit substance use is normalized.

Novel correlate: hospitalization frequency

The emergence of hospitalization frequency as a variable associated with illicit substance use (AOR = 1.29 per admission) signals a clinically critical pattern. This aligns with several studies linking repeated hospitalizations to severe dual-diagnosis trajectories [23,26], suggesting that each admission may represent accumulated neurobiological vulnerability or systemic failures in continuity of care. In LUTH’s resource-constrained setting, this association may also reflect cyclical crises where illicit substance use precipitates relapse, driving rehospitalization, a feedback loop demanding integrated inpatient substance interventions.

Dissociation of bivariate predictors

The loss of significance for violent behavior, negative symptoms, awareness of illness, and medication adherence in adjusted models highlights confounding pathways. For instance, violence (OR=3.25, p < 0.0001 bivariately) may stem from substance-induced impulsivity rather than schizophrenia psychopathology, consistent with neurobiological models of addiction-psychosis interactions [27,28]. Similarly, medication non-adherence likely operates downstream of substance use (e.g., cognitive impairment from alcohol), explaining its attenuation when substance behaviours are modelled. The non-retention of negative symptoms contradicts the “self-medication” hypothesis [28], implying transient symptom alleviation by substances does not translate to population-level protection.

Clinical and policy implications

The association of education (AOR = 0.44) advocates for socioeconomic interventions like vocational training to disrupt poverty-substance use cycles. Similarly, marital stability and gender-specific associations necessitate family-inclusive counselling and male-targeted harm reduction. The hospitalization finding demands systemic reforms: embedding addiction specialists in inpatient psychiatry teams and post-discharge monitoring. It is important to note that the final logistic regression model showed evidence of poor calibration (Hosmer-Lemeshow p = 0.0196), which may affect the reliability of the predicted probabilities. However, the model demonstrated good discriminative ability. Limitations include recall bias in hospitalization documentation and ASSIST’s potential cultural insensitivity to local substances like kachasu. Furthermore, continuous predictors like age and number of hospitalizations were modeled as linear terms; their relationship with illicit substance use may be non-linear, an assumption that was not tested and represents a potential limitation. Finally, the cross-sectional design precludes causal inference.

Conclusion

This study found a prevalence of illicit substance use of 31.1% among persons with schizophrenia at LUTH. Male gender, alcohol use, and tobacco smoking were associated with illicit substance use, but multivariable analysis reveals associations for female sex, marriage, parental loss, and education with lower odds of use, alongside hospitalization frequency as a novel correlate. To mitigate this comorbidity, we recommend: (1) integrating gender-specific substance screening in psychiatric care, (2) socioeconomic programs targeting education and employment, (3) family-centered interventions leveraging marital and kinship support, and (4) specialized addiction services for frequently hospitalized patients. Validating assessment tools for Zambian cultural contexts and longitudinal studies to clarify causality are essential next steps.

Supporting information

S1 Checklist. Strobe checklist.

(DOCX)

pgph.0005024.s001.docx^{(32.2KB, docx)}

S1 Table. Variance inflation factor for the variables.

(DOCX)

pgph.0005024.s002.docx^{(18.6KB, docx)}

S2 Table. Logistic regression model and statistical performance metrics.

(DOCX)

pgph.0005024.s003.docx^{(231.9KB, docx)}

S3 Table. Detailed best model performance model, cross validation and calibration metrics.

(DOCX)

pgph.0005024.s004.docx^{(23.5KB, docx)}

S1 Data. Minimal dataset.

(XLSX)

pgph.0005024.s005.xlsx^{(57.7KB, xlsx)}

Data Availability

The raw data underlying the results presented in the study have been uploaded as supporting information.

Funding Statement

The authors received no specific funding for this work.

References

1.Solmi M, Seitidis G, Mavridis D, Correll CU, Dragioti E, Guimond S, et al. Incidence, prevalence, and global burden of schizophrenia - data, with critical appraisal, from the Global Burden of Disease (GBD) 2019. Mol Psychiatry. 2023;28(12):5319–27. doi: 10.1038/s41380-023-02138-4 [DOI] [PubMed] [Google Scholar]
2.Tandon R, Gaebel W, Barch DM, Bustillo J, Gur RE, Heckers S, et al. Definition and description of schizophrenia in the DSM-5. Schizophr Res. 2013;150(1):3–10. doi: 10.1016/j.schres.2013.05.028 [DOI] [PubMed] [Google Scholar]
3.Cuffel BJ. Prevalence estimates of substance abuse in schizophrenia and their correlates. J Nerv Ment Dis. 1992;180(9):589–92; discussion 593-6. doi: 10.1097/00005053-199209000-00008 [DOI] [PubMed] [Google Scholar]
4.Alexander L. Mental Health in Zambia: 5 Facts. In: The Borgen Project [Internet]. 1. Sept 2023 [cited 7 July 2025]. Available: https://borgenproject.org/mental-health-in-zambia-2/ [Google Scholar]
5.Mayeya J, Chazulwa R, Mayeya PN, Mbewe E, Magolo LM, Kasisi F, et al. Zambia mental health country profile. Int Rev Psychiatry. 2004;16(1–2):63–72. doi: 10.1080/09540260310001635113 [DOI] [PubMed] [Google Scholar]
6.Schizophrenia Working Group of the Psychiatric Genomics Consortium. Biological insights from 108 schizophrenia-associated genetic loci. Nature. 2014;511(7510):421–7. doi: 10.1038/nature13595 [DOI] [PMC free article] [PubMed] [Google Scholar]
7.Batel P. Addiction and schizophrenia. Eur Psychiatry. 2000;15(2):115–22. doi: 10.1016/s0924-9338(00)00203-0 [DOI] [PubMed] [Google Scholar]
8.Verma SK, Subramaniam M, Chong S-A, Kua EH. Substance abuse in schizophrenia. A Singapore perspective. Soc Psychiatry Psychiatr Epidemiol. 2002;37(7):326–8. doi: 10.1007/s00127-002-0553-8 [DOI] [PubMed] [Google Scholar]
9.Soyka M. Alcohol dependence and schizophrenia: what are the interrelationships?. Alcohol Alcohol Suppl. 1994;2:473–8. [PubMed] [Google Scholar]
10.Khungar V, Poordad F. Management of overt hepatic encephalopathy. Clin Liver Dis. 2012;16(1):73–89. doi: 10.1016/j.cld.2011.12.007 [DOI] [PubMed] [Google Scholar]
11.Bellack AS, Gearon JS. Substance abuse treatment for people with schizophrenia. Addict Behav. 1998;23(6):749–66. doi: 10.1016/s0306-4603(98)00066-5 [DOI] [PubMed] [Google Scholar]
12.World Mental Health Report 2022. – Centre for Knowledge and Development. [cited 1 May 2025]. Available: https://www.ipeckd.org/world-mental-health-report-2022/ [Google Scholar]
13.Onaolapo OJ, Olofinnade AT, Ojo FO, Adeleye O, Falade J, Onaolapo AY. Substance use and substance use disorders in Africa: An epidemiological approach to the review of existing literature. World J Psychiatry. 2022;12(10):1268–86. doi: 10.5498/wjp.v12.i10.1268 [DOI] [PMC free article] [PubMed] [Google Scholar]
14.Emmanuel GO, Akinsolu FT, Abodunrin OR, Ezechi OC. Prevalence and patterns of substance use in West Africa: A systematic review and meta-analysis. PLOS Glob Public Health. 2024;4(12):e0004019. doi: 10.1371/journal.pgph.0004019 [DOI] [PMC free article] [PubMed] [Google Scholar]
15.Kibru B, Tesfaw G, Demilew D, Salelew E. The Prevalence and Correlates of Social Anxiety Symptoms among People with Schizophrenia in Ethiopia: An Institution-Based Cross-Sectional Study. Schizophr Res Treatment. 2020;2020:3934680. doi: 10.1155/2020/3934680 [DOI] [PMC free article] [PubMed] [Google Scholar]
16.Nesvåg R, Knudsen GP, Bakken IJ, Høye A, Ystrom E, Surén P, et al. Substance use disorders in schizophrenia, bipolar disorder, and depressive illness: a registry-based study. Soc Psychiatry Psychiatr Epidemiol. 2015;50(8):1267–76. doi: 10.1007/s00127-015-1025-2 [DOI] [PubMed] [Google Scholar]
17.Yapici Eser H, Kacar AS, Kilciksiz CM, Yalçinay-Inan M, Ongur D. Prevalence and Associated Features of Anxiety Disorder Comorbidity in Bipolar Disorder: A Meta-Analysis and Meta-Regression Study. Front Psychiatry. 2018;9:229. doi: 10.3389/fpsyt.2018.00229 [DOI] [PMC free article] [PubMed] [Google Scholar]
18.Chinyama J, Menon AJ. Mental Health and Healthcare Provision in Zambian Correctional Facilities. mjz. 2020;47(3):208–14. doi: 10.55320/mjz.47.3.88 [DOI] [Google Scholar]
19.Zyambo C, Phiri MM, Zulu R, Mukupa M, Mabanti K, Matenga TFL, et al. Illicit alcohol consumption and its associated factors among patrons in Zambia: a cross-sectional analytical study. Front Public Health. 2025;13:1444304. doi: 10.3389/fpubh.2025.1444304 [DOI] [PMC free article] [PubMed] [Google Scholar]
20.van Os J, Rutten BP, Poulton R. Gene-environment interactions in schizophrenia: review of epidemiological findings and future directions. Schizophr Bull. 2008;34(6):1066–82. doi: 10.1093/schbul/sbn117 [DOI] [PMC free article] [PubMed] [Google Scholar]
21.Stilo SA, Murray RM. Non-Genetic Factors in Schizophrenia. Curr Psychiatry Rep. 2019;21(10):100. doi: 10.1007/s11920-019-1091-3 [DOI] [PMC free article] [PubMed] [Google Scholar]
22.Chang S, Jeyagurunathan A, Lau JH, Shafie S, Samari E, Cetty L, et al. Problematic Drug Use Among Outpatients With Schizophrenia and Related Psychoses. Front Psychiatry. 2021;12:762988. doi: 10.3389/fpsyt.2021.762988 [DOI] [PMC free article] [PubMed] [Google Scholar]
23.Tumenta T, Oladeji O, Gill M, Khan BA, Olayinka O, Ojimba C, et al. Substance Use Patterns and Schizophrenia Spectrum Disorders: A Retrospective Study of Inpatients at a Community Teaching Hospital. J Clin Med Res. 2020;12(12):803–8. doi: 10.14740/jocmr4380 [DOI] [PMC free article] [PubMed] [Google Scholar]
24.Abbasi LN, Daradkeh TK, ElWasify M, Abassy S. Prevalence of substance use among a sample of patients attending an outpatient psychiatric clinic in Amman, Jordan. Discov Ment Health. 2024;4(1):57. doi: 10.1007/s44192-024-00113-1 [DOI] [PMC free article] [PubMed] [Google Scholar]
25.Negrete JC. Clinical aspects of substance abuse in persons with schizophrenia. Can J Psychiatry. 2003;48(1):14–21. doi: 10.1177/070674370304800104 [DOI] [PubMed] [Google Scholar]
26.Bennett ME, Brown CH, Peer J, Li L, Bellack AS. Patterns and Predictors of Changes in Substance Use in Individuals with Schizophrenia and Affective Disorders. J Dual Diagn. 2012;8(1):2–12. doi: 10.1080/15504263.2012.647466 [DOI] [PMC free article] [PubMed] [Google Scholar]
27.Ward HB, Nemeroff CB, Carpenter L, Grzenda A, McDonald WM, Rodriguez CI, et al. Substance use disorders in schizophrenia: Prevalence, etiology, biomarkers, and treatment. Personalized Medicine in Psychiatry. 2023;39–40:100106. doi: 10.1016/j.pmip.2023.100106 [DOI] [Google Scholar]
28.Khokhar JY, Dwiel LL, Henricks AM, Doucette WT, Green AI. The link between schizophrenia and substance use disorder: A unifying hypothesis. Schizophr Res. 2018;194:78–85. doi: 10.1016/j.schres.2017.04.016 [DOI] [PMC free article] [PubMed] [Google Scholar]

PLOS Glob Public Health. doi: 10.1371/journal.pgph.0005024.r001

Decision Letter 0

Feten Fekih-Romdhane

6 Jun 2025

PGPH-D-25-01149

Prevalence and Factors Associated with Substance Abuse Among Schizophrenic Patients at LUTH in Zambia

PLOS Global Public Health

Dear Dr. Masenga,

Thank you for submitting your manuscript to PLOS Global Public Health. After careful consideration, we feel that it has merit but does not fully meet PLOS Global Public Health’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 21 2025 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 globalpubhealth@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pgph/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

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Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

We look forward to receiving your revised manuscript.

Kind regards,

Feten Fekih-Romdhane

Academic Editor

PLOS Global Public Health

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Does this manuscript meet PLOS Global Public Health’s publication criteria?>

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available (please refer to the Data Availability Statement at the start of the manuscript PDF file)??>

The PLOS Data policy

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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Reviewer #1: Overall: I would like to thank for inviting to review this manuscript. This study will have great value in sub-Saharan countries to enhance awareness and prevention strategies for mental health wellbeing and its association with substance use disorders. I hope this manuscript described well.

I have few comments, find it below

Comments

Abstract section

1. The word alcohol (kachasu) mentioned, what does ‘kachasu’ mean? Is it Zambian language for alcohol or not? If you misspelled kaht use revise it

2. DSM-5 or DSM-5TR currently defines substance use rather than substance abuse. Since the word abuse is inappropriate term and increase negative view on substance users. It is better to replace substance abuse by substance use in your whole document

3. ‘Ethical approval and informed consent were obtained’ put this statement in ethical consideration section only.

Introduction/Background

1. ‘Yet the country has only five psychiatrists’. This statement is for whole Zambian country or the only for University Teaching Hospital (LUTH). Make clear this statement otherwise it seems like exaggeration of the problems

Method

1. The data collected from patient medical recorded or secondary data might be prone to biased information, what you did to minimize bias in your study? Describe this carefully in the limitation section

2. Describe smartly about the data quality assurance since the secondary data need more attention to minimize missed information.

3. What you did for participants who had substance use disorder after screening? If you did something, please specify it?

Result section

1. For the variables Age and Number of hospitalizations has reference category not specified why? Use the same format for all variables.

Discussion

1. ‘In this study the prevalence of substance abuse was 31.1% (94/303). Alcohol use (60.2% vs.46 13.7% non-users, p<0.001) and smoking (61.5% vs. 15.1% non-smokers, p<0.001)’. Please discuss this finding with others study which have similar, higher or below finding compared to this study by giving convincing scientific evidences

Limitations, Recommendation and conclusion

1. Describe limitation in detail

2. Conclusion Should be smart, short and prices

3. Recommendation based on finding, be carefully about this

4. Is it ASSIT valid in Zambia? If not valid it is better to recommend future study to do validation.

Overall: be carefully about grammar, paraphrasing and correct reference

Finally; - thank you for your contribution to existing body of knowledge’s and submitting your manuscript to PLOS Global Public Health

Reviewer #2: Dear Author,

Thanks for submitting the article.

Following are my suggestions :

1. Clearly define "substance abuse" to align with ICD-10, including alcohol (F10) and nicotine (F17). Ensure consistency across methodology and results to avoid confusion.

2. Include a power calculation to justify the sample size of 302 participants. This is necessary to confirm the study’s ability to detect associations. Eg for rare variables like suicidal behavior (n=3).

3. Analyze the 538 excluded records (64% of 840) to assess systematic differences from included cases. High exclusion rates may introduce bias.

4. Provide details on the quality and consistency of medical record documentation. Specify any quality checks or standardization processes applied.

5. State the criteria for selecting variables for multivariable logistic regression, such as p<0.05 in univariable analysis or theoretical relevance.

6. Assess collinearity between predictors, such as alcohol use and smoking, using variance inflation factor (VIF) or correlation matrices. Report goodness-of-fit with tests like Hosmer-Lemeshow.

7. Explain wide confidence intervals, such as for male sex (AOR=5.21, 95% CI: 1.75–15.63).

8. Limit the scope of results to tertiary settings similar to LUTH. From a single-center study, this cannot be claimed as “nationally representative data”.

Thank you

Regards

Reviewer #3: General comments and some key concerns:

The manuscript is addressing an important issue on “Prevalence and Factors Associated with Substance Abuse among Schizophrenic Patients at LUTH in Zambia”. Substance Abuse and use has remained a global challenge in the population including the Schizophrenic Patients with limited data on the extent of their use among this population. However, there are some comments that need to be addressed as below.

• The authors should use past tense when reporting in the manuscript and some sentences are too long and hence losing the intended meaning. The sentence in line 19-21 need to be split up to get a clear meaning.

1. Abstract

The authors should include a sub-section on the aim or objectives of the study just after the background. Authors should also include the summary of data analysis plan in the methods.

2. Introduction

In the line 66, the authors should insert Introduction instead of Background. The authors should incorporate the objective(s) of the study at the end of the sub-section

3. Methods section

The study design is not clear and the authors should think through it since in the abstract it is a different design. The authors should include a sub-section on the study population i.e. target population, accessible population and the actual study population recruited in the study just before eligibility and recruitment. Furthermore, the study populations are schizophrenic patients and they have lost reality of the world and therefore the responses they give may not be well connected. Which type of schizophrenic patients’ records were used or participated in the study? In the abstract, data was collected using structured interviews, validated tools (Alcohol, Smoking, and Substance Involvement Screening Test [ASSIST]), but in the methods medical records were used, how were interviews made on the records?

4. Results

In table 1, demographic characteristics, the authors should include the units of age, and since the main measure is % and not frequencies, the authors should use % (n) and not the reverse. The total number of participants was 302, but in table 1, some items responses exceed that number. The authors should check this throughout the table. In table2, there is a strong association of Violent Behavior and substance use, how do violent behaviors lead to substance abuse?

5. Discussion

The authors should split the discussion if possible based on the study objectives so that it is clear i.e. demographic characteristics, substance use and associated risk factors.

6. Conclusion

The authors should have a sub-section of conclusions in the manuscript and not entangled in the discussion. And the conclusion made neither is nor supported by the findings of the study and therefore it needs to be re-written.

6. References

Further citations are needed to be included to support the background to the study and the authors should also follow the recommended Journal reference style.

**********

what does this mean? ). If published, this will include your full peer review and any attached files.

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Reviewer #1: Yes: Tamene Berhanu Alaho

Reviewer #2: Yes: Karthik Balajee Laksham

Reviewer #3: No

**********

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Attachment

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PLOS Glob Public Health. 2026 Jan 12;6(1):e0005024. doi: 10.1371/journal.pgph.0005024.r002

Author response to Decision Letter 1

22 Jul 2025

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Submitted filename: Response to Reviewers.docx

pgph.0005024.s007.docx^{(976.9KB, docx)}

PLOS Glob Public Health. doi: 10.1371/journal.pgph.0005024.r003

Decision Letter 1

Feten Fekih-Romdhane

4 Sep 2025

PGPH-D-25-01149R1

Prevalence and Factors Associated with Substance use Among Schizophrenic Patients at a Tertiary Referral Hospital in Zambia

PLOS Global Public Health

Dear Dr. Masenga,

==============================

EDITOR:

The manuscript contains causal language (e.g., “predictors”), which is inappropriate given the cross-sectional design. Such statements are misleading and should be removed. The authors should revise these statements to reflect correlational findings.

The use of labeling and stigmatizing language is not accepted. Stigmatizing phrases, such as “schizophrenic patients”, should all be removed throughout the paper. The title should also be revised accordingly.

Clear objectives and hypotheses should be formulated at the end of the introduction. Inclusion criteria should be further detailed (outpatients or inpatients? clinical remission? schizophrenia according to which criteria? who made the diagnosis?).

The methods section is poorly informed. More details are required about how clinical variables were assessed (hallucinations, delusions, disorganized speech, disorganized behavior, negative symptoms, cognitive impairment, suicidality and self-harm).

==============================

Please submit your revised manuscript by . If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at globalpubhealth@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pgph/ 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 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'.

Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

We look forward to receiving your revised manuscript.

Kind regards,

Feten Fekih-Romdhane

Academic Editor

PLOS Global Public Health

Journal Requirements:

If the reviewer comments include a recommendation to cite specific previously published works, please review and evaluate these publications to determine whether they are relevant and should be cited. There is no requirement to cite these works unless the editor has indicated otherwise.

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

Additional Editor Comments (if provided):

Reviewer #1:

Reviewer #3:

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

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

Reviewer #1: All comments have been addressed

Reviewer #3: All comments have been addressed

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publication criteria?>

Reviewer #1: Yes

Reviewer #3: Yes

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

Reviewer #1: Yes

Reviewer #3: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available (please refer to the Data Availability Statement at the start of the manuscript PDF file)??>

The PLOS Data policy

Reviewer #1: Yes

Reviewer #3: Yes

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

Reviewer #1: Yes

Reviewer #3: Yes

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Reviewer #1: I have no comments

Reviewer #3: General comments and some key concerns:

The authors have tried to address all the comments raised in the paper and congratulate them. However, there still some few issues that needs to be addressed.

1. Abstract

The objective in the abstract should be complete (see the title). The conclusion drawn by the authors in the abstract are not in line with the objective and the title. Therefore, the authors need to paraphrase the conclusion. The authors need to be clear on the sentence (line 35-36), “Data were collected from medical records including records of structured interviews with validated tools…”, were the structured interviews information retrieved also from records or from the medical records, that is when the study participants were contacted for the interview? The authors need to clarify on this.

2. Introduction

The authors need to improve the grammar on the sentence (Line 88-91). And the objective of the study also needs to be improved i.e. stated clearly for easy understanding.

3. Methods section

According to the study design, which is the retrospective cross-sectional study, as mentioned above “Data were collected from medical records including records of structured interviews with validated tools…”, were the structured interviews information retrieved also from records or from the medical records, that is when the study participants were contacted for the interview? The authors need to clarify on this. Line 144, no patient interviews were conducted; the authors need to clear how information from the structured interviews mentioned in the abstract were obtained. Line 121, the authors should avoid starting a sentence with a value.

4. Results

Line 296, the authors mention “smoking”, which smoking is being referred in the paper?

6. Conclusion

The authors should also conclude on the prevalence since it is key in the title.

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what does this mean? ). If published, this will include your full peer review and any attached files.

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Reviewer #1: Yes: Tamene Berhanu Alaho

Reviewer #3: No

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PLOS Glob Public Health. 2026 Jan 12;6(1):e0005024. doi: 10.1371/journal.pgph.0005024.r004

Author response to Decision Letter 2

12 Sep 2025

Attachment

Submitted filename: RESPONSES TO EDITOR AND REVIEWER COMMENTS.docx

pgph.0005024.s008.docx^{(19.1KB, docx)}

PLOS Glob Public Health. doi: 10.1371/journal.pgph.0005024.r005

Decision Letter 2

Feten Fekih-Romdhane

22 Oct 2025

PGPH-D-25-01149R2

Prevalence and Factors Associated with Substance use Among Persons with Schizophrenia at a Tertiary Referral Hospital in Zambia

PLOS Global Public Health

Dear Dr. Masenga,

Please submit your revised manuscript by Dec 06 2025 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 globalpubhealth@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pgph/ 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 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'.

Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

We look forward to receiving your revised manuscript.

Kind regards,

Feten Fekih-Romdhane

Academic Editor

PLOS Global Public Health

Journal Requirements:

Additional Editor Comments (if provided):

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

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

Reviewer #3: All comments have been addressed

Reviewer #4: All comments have been addressed

Reviewer #5: (No Response)

Reviewer #6: All comments have been addressed

Reviewer #7: (No Response)

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publication criteria?>

Reviewer #3: Yes

Reviewer #4: Partly

Reviewer #5: Yes

Reviewer #6: Yes

Reviewer #7: Yes

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

Reviewer #3: Yes

Reviewer #4: Yes

Reviewer #5: I don't know

Reviewer #6: Yes

Reviewer #7: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available (please refer to the Data Availability Statement at the start of the manuscript PDF file)??>

The PLOS Data policy

Reviewer #3: Yes

Reviewer #4: Yes

Reviewer #5: Yes

Reviewer #6: Yes

Reviewer #7: Yes

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

Reviewer #3: Yes

Reviewer #4: No

Reviewer #5: Yes

Reviewer #6: Yes

Reviewer #7: Yes

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Reviewer #3: Abstract

Line 29 -31: Objective should be revised as “This study determined the prevalence and factors associated with substance use among adults with schizophrenia at the University Teaching Hospital (LUTH) in Zambia

Introduction

Line 99 -101: The suggested study objective is “The study determined the prevalence and factors associated with substance use among adults with schizophrenia at the University Teaching Hospital (LUTH) in Zambia”.

Results

Line 304: The statement “Conversely, Alcohol Use was strongly associated with substance use”, what does this mean? Alcohol is also a substance!!!

Reviewer #4: Major Revision. The study is important, but clarification of methods, removal of redundancy, and careful editing for consistency are needed.

Reviewer #5: Summary and Overall Assessment

This manuscript is well-crafted and presents meaningful findings. The study is methodologically robust, and the results are clearly articulated. It makes a valuable contribution to the field, enhancing our understanding of the topic. I recommend minor revisions to enhance clarity, formatting, and alignment with the journal's guidelines before final acceptance.

Strengths

• The research objectives are clearly stated, and the methodology is appropriately designed.

• The results are logically organised and supported by relevant data.

• The discussion thoughtfully integrates the findings with existing literature and highlights important public health implications.

Areas for Improvement

- Abstract Length: The abstract currently exceeds the 300-word limit set by PLOS Public Health. Please revise it to be more concise while retaining essential information.

- Reference Formatting: Some references are missing DOI numbers. Kindly verify and update all references to include DOIs where available.

- Language and Style: Minor grammatical and typographical errors are present throughout the manuscript. A thorough proofreading is recommended.

Final Remarks

Overall, this is a well-structured and informative study that offers valuable insights for public health research. With the above minor revisions, the manuscript will be well-positioned for publication in PLOS Public Health.

Reviewer #6: Congratulations to the authors! This is a very well-written paper, and all previous comments have been addressed appropriately.

I have very minor comments for the authors:

1) Clarify that you are assessing psychoactive substance use earlier in the paper, as substance use can sometimes be an umbrella term and include alcohol and/or tobacco use. This can be a bit confusing and the first mention of psychoactive substance use is in the methods.

2) Cite the software used for analysis.

3) Cite the statistical standards and threshold described in the methods.

Other than these, I think this paper is ready.

Reviewer #7: This cross-sectional study explores substance use among persons with schizophrenia in Zambia, addressing a critical evidence gap in both the local and broader sub-Saharan African literature. The study offers valuable insights into a population at high risk for substance use disorders.

Main Strengths

1. The study addresses a clear evidence gap within Zambia’s mental health system.

2. It meets STROBE reporting standards, enhancing transparency and reproducibility.

3. Clinical and sociodemographic variables were appropriately selected and comprehensively assessed.

4. Statistical methods were rigorous, with multivariable modeling, collinearity diagnostics, and model fit procedures clearly reported.

Points for Improvement

1. In broader literature, “substance use” typically includes tobacco, alcohol, and other drugs. Excluding tobacco and alcohol may confuse readers. A more accurate term might be illicit substance use to reflect the study's classification of other drugs.

2. The final logistic regression model demonstrated poor calibration (Hosmer-Lemeshow p = 0.0196), raising concerns about the model’s fit. The reliability of the associations could be improved by re-estimating the model using penalized regression or by reducing the number of predictors.

3. Continuous predictors like age and number of hospitalizations were modeled linearly. However, their relationship with substance use may be non-linear. The analysis would benefit from assessing this assumption using methods such as the Box-Tidwell test or by modeling non-linearity with splines or categorized versions.

4. While adjusted predictors are clearly reported, some variables significant in bivariate analysis (e.g., negative symptoms, awareness of diagnosis) were omitted from the final model without explanation. Clarifying whether these were excluded based on stepwise selection or clinical irrelevance would enhance transparency.

Minor Comments

Descriptive tables should include 95% confidence intervals for proportions to improve interpretability and comparability across groups.

Overall, this is a timely and relevant study. The analytical approach is largely sound and well-reported. Nonetheless, addressing modeling assumptions, clarifying variable inclusion decisions, and improving model calibration would strengthen the robustness of the findings.

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what does this mean? ). If published, this will include your full peer review and any attached files.

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For information about this choice, including consent withdrawal, please see our Privacy Policy

Reviewer #3: No

Reviewer #4: Yes: Fathi Ali Araye

Reviewer #5: No

Reviewer #6: No

Reviewer #7: Yes: Honest Anaba

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Attachment

Submitted filename: Schizophrenia Manuscript track changes last review.docx

pgph.0005024.s009.docx^{(88.1KB, docx)}

Attachment

Submitted filename: Manuscript Review Report.docx

pgph.0005024.s010.docx^{(27.4KB, docx)}

PLOS Glob Public Health. 2026 Jan 12;6(1):e0005024. doi: 10.1371/journal.pgph.0005024.r006

Author response to Decision Letter 3

13 Nov 2025

Attachment

Submitted filename: Responses to reviewers.docx

pgph.0005024.s011.docx^{(22KB, docx)}

PLOS Glob Public Health. doi: 10.1371/journal.pgph.0005024.r007

Decision Letter 3

Yatan Pal Singh Balhara

22 Dec 2025

Prevalence and Factors Associated with illicit Substance use Among Persons with Schizophrenia at a Tertiary Referral Hospital in Zambia

PGPH-D-25-01149R3

Dear Prof. Masenga,

We are pleased to inform you that your manuscript 'Prevalence and Factors Associated with illicit Substance use Among Persons with Schizophrenia at a Tertiary Referral Hospital in Zambia' has been provisionally accepted for publication in PLOS Global Public Health.

Before your manuscript can be formally accepted you will need to complete some formatting changes, which you will receive in a follow up email. A member of our team will be in touch with a set of requests.

Please note that your manuscript will not be scheduled for publication until you have made the required changes, so a swift response is appreciated.

IMPORTANT: The editorial review process is now complete. PLOS will only permit corrections to spelling, formatting or significant scientific errors from this point onwards. Requests for major changes, or any which affect the scientific understanding of your work, will cause delays to the publication date of your manuscript.

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 globalpubhealth@plos.org.

Thank you again for supporting Open Access publishing; we are looking forward to publishing your work in PLOS Global Public Health.

Best regards,

Yatan Pal Singh Balhara

Academic Editor

PLOS Global Public Health

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Reviewer Comments (if any, and for reference):

Reviewer's Responses to Questions

Comments to the Author

Reviewer #4: All comments have been addressed

Reviewer #6: All comments have been addressed

**********

publication criteria?>

Reviewer #4: Yes

Reviewer #6: Yes

**********

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

Reviewer #4: Yes

Reviewer #6: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available (please refer to the Data Availability Statement at the start of the manuscript PDF file)??>

The PLOS Data policy

Reviewer #4: Yes

Reviewer #6: Yes

**********

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

Reviewer #4: Yes

Reviewer #6: Yes

**********

Reviewer #4: (No Response)

Reviewer #6: I think paper is bridging a major gap in the study of illicit substance use among people with schizophrenia in a resource-constrained environment.

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what does this mean? ). If published, this will include your full peer review and any attached files.

Do you want your identity to be public for this peer review? If you choose “no”, your identity will remain anonymous but your review may still be made public.

For information about this choice, including consent withdrawal, please see our Privacy Policy

Reviewer #4: Yes: Fathi Araye

Reviewer #6: No

**********

Attachment

Submitted filename: recommendation letter.docx

pgph.0005024.s012.docx^{(12KB, docx)}

Associated Data

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

Supplementary Materials

S1 Checklist. Strobe checklist.

(DOCX)

pgph.0005024.s001.docx^{(32.2KB, docx)}

S1 Table. Variance inflation factor for the variables.

(DOCX)

pgph.0005024.s002.docx^{(18.6KB, docx)}

S2 Table. Logistic regression model and statistical performance metrics.

(DOCX)

pgph.0005024.s003.docx^{(231.9KB, docx)}

S3 Table. Detailed best model performance model, cross validation and calibration metrics.

(DOCX)

pgph.0005024.s004.docx^{(23.5KB, docx)}

S1 Data. Minimal dataset.

(XLSX)

pgph.0005024.s005.xlsx^{(57.7KB, xlsx)}

Attachment

Submitted filename: Comment by Tamene Berhanu May 29, 2025.docx

pgph.0005024.s006.docx^{(19KB, docx)}

Attachment

Submitted filename: Response to Reviewers.docx

pgph.0005024.s007.docx^{(976.9KB, docx)}

Attachment

Submitted filename: RESPONSES TO EDITOR AND REVIEWER COMMENTS.docx

pgph.0005024.s008.docx^{(19.1KB, docx)}

Attachment

Submitted filename: Schizophrenia Manuscript track changes last review.docx

pgph.0005024.s009.docx^{(88.1KB, docx)}

Attachment

Submitted filename: Manuscript Review Report.docx

pgph.0005024.s010.docx^{(27.4KB, docx)}

Attachment

Submitted filename: Responses to reviewers.docx

pgph.0005024.s011.docx^{(22KB, docx)}

Attachment

Submitted filename: recommendation letter.docx

pgph.0005024.s012.docx^{(12KB, docx)}

Data Availability Statement

The raw data underlying the results presented in the study have been uploaded as supporting information.

[pgph.0005024.ref001] 1.Solmi M, Seitidis G, Mavridis D, Correll CU, Dragioti E, Guimond S, et al. Incidence, prevalence, and global burden of schizophrenia - data, with critical appraisal, from the Global Burden of Disease (GBD) 2019. Mol Psychiatry. 2023;28(12):5319–27. doi: 10.1038/s41380-023-02138-4 [DOI] [PubMed] [Google Scholar]

[pgph.0005024.ref002] 2.Tandon R, Gaebel W, Barch DM, Bustillo J, Gur RE, Heckers S, et al. Definition and description of schizophrenia in the DSM-5. Schizophr Res. 2013;150(1):3–10. doi: 10.1016/j.schres.2013.05.028 [DOI] [PubMed] [Google Scholar]

[pgph.0005024.ref003] 3.Cuffel BJ. Prevalence estimates of substance abuse in schizophrenia and their correlates. J Nerv Ment Dis. 1992;180(9):589–92; discussion 593-6. doi: 10.1097/00005053-199209000-00008 [DOI] [PubMed] [Google Scholar]

[pgph.0005024.ref004] 4.Alexander L. Mental Health in Zambia: 5 Facts. In: The Borgen Project [Internet]. 1. Sept 2023 [cited 7 July 2025]. Available: https://borgenproject.org/mental-health-in-zambia-2/ [Google Scholar]

[pgph.0005024.ref005] 5.Mayeya J, Chazulwa R, Mayeya PN, Mbewe E, Magolo LM, Kasisi F, et al. Zambia mental health country profile. Int Rev Psychiatry. 2004;16(1–2):63–72. doi: 10.1080/09540260310001635113 [DOI] [PubMed] [Google Scholar]

[pgph.0005024.ref006] 6.Schizophrenia Working Group of the Psychiatric Genomics Consortium. Biological insights from 108 schizophrenia-associated genetic loci. Nature. 2014;511(7510):421–7. doi: 10.1038/nature13595 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pgph.0005024.ref007] 7.Batel P. Addiction and schizophrenia. Eur Psychiatry. 2000;15(2):115–22. doi: 10.1016/s0924-9338(00)00203-0 [DOI] [PubMed] [Google Scholar]

[pgph.0005024.ref008] 8.Verma SK, Subramaniam M, Chong S-A, Kua EH. Substance abuse in schizophrenia. A Singapore perspective. Soc Psychiatry Psychiatr Epidemiol. 2002;37(7):326–8. doi: 10.1007/s00127-002-0553-8 [DOI] [PubMed] [Google Scholar]

[pgph.0005024.ref009] 9.Soyka M. Alcohol dependence and schizophrenia: what are the interrelationships?. Alcohol Alcohol Suppl. 1994;2:473–8. [PubMed] [Google Scholar]

[pgph.0005024.ref010] 10.Khungar V, Poordad F. Management of overt hepatic encephalopathy. Clin Liver Dis. 2012;16(1):73–89. doi: 10.1016/j.cld.2011.12.007 [DOI] [PubMed] [Google Scholar]

[pgph.0005024.ref011] 11.Bellack AS, Gearon JS. Substance abuse treatment for people with schizophrenia. Addict Behav. 1998;23(6):749–66. doi: 10.1016/s0306-4603(98)00066-5 [DOI] [PubMed] [Google Scholar]

[pgph.0005024.ref012] 12.World Mental Health Report 2022. – Centre for Knowledge and Development. [cited 1 May 2025]. Available: https://www.ipeckd.org/world-mental-health-report-2022/ [Google Scholar]

[pgph.0005024.ref013] 13.Onaolapo OJ, Olofinnade AT, Ojo FO, Adeleye O, Falade J, Onaolapo AY. Substance use and substance use disorders in Africa: An epidemiological approach to the review of existing literature. World J Psychiatry. 2022;12(10):1268–86. doi: 10.5498/wjp.v12.i10.1268 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pgph.0005024.ref014] 14.Emmanuel GO, Akinsolu FT, Abodunrin OR, Ezechi OC. Prevalence and patterns of substance use in West Africa: A systematic review and meta-analysis. PLOS Glob Public Health. 2024;4(12):e0004019. doi: 10.1371/journal.pgph.0004019 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pgph.0005024.ref015] 15.Kibru B, Tesfaw G, Demilew D, Salelew E. The Prevalence and Correlates of Social Anxiety Symptoms among People with Schizophrenia in Ethiopia: An Institution-Based Cross-Sectional Study. Schizophr Res Treatment. 2020;2020:3934680. doi: 10.1155/2020/3934680 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pgph.0005024.ref016] 16.Nesvåg R, Knudsen GP, Bakken IJ, Høye A, Ystrom E, Surén P, et al. Substance use disorders in schizophrenia, bipolar disorder, and depressive illness: a registry-based study. Soc Psychiatry Psychiatr Epidemiol. 2015;50(8):1267–76. doi: 10.1007/s00127-015-1025-2 [DOI] [PubMed] [Google Scholar]

[pgph.0005024.ref017] 17.Yapici Eser H, Kacar AS, Kilciksiz CM, Yalçinay-Inan M, Ongur D. Prevalence and Associated Features of Anxiety Disorder Comorbidity in Bipolar Disorder: A Meta-Analysis and Meta-Regression Study. Front Psychiatry. 2018;9:229. doi: 10.3389/fpsyt.2018.00229 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pgph.0005024.ref018] 18.Chinyama J, Menon AJ. Mental Health and Healthcare Provision in Zambian Correctional Facilities. mjz. 2020;47(3):208–14. doi: 10.55320/mjz.47.3.88 [DOI] [Google Scholar]

[pgph.0005024.ref019] 19.Zyambo C, Phiri MM, Zulu R, Mukupa M, Mabanti K, Matenga TFL, et al. Illicit alcohol consumption and its associated factors among patrons in Zambia: a cross-sectional analytical study. Front Public Health. 2025;13:1444304. doi: 10.3389/fpubh.2025.1444304 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pgph.0005024.ref020] 20.van Os J, Rutten BP, Poulton R. Gene-environment interactions in schizophrenia: review of epidemiological findings and future directions. Schizophr Bull. 2008;34(6):1066–82. doi: 10.1093/schbul/sbn117 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pgph.0005024.ref021] 21.Stilo SA, Murray RM. Non-Genetic Factors in Schizophrenia. Curr Psychiatry Rep. 2019;21(10):100. doi: 10.1007/s11920-019-1091-3 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pgph.0005024.ref022] 22.Chang S, Jeyagurunathan A, Lau JH, Shafie S, Samari E, Cetty L, et al. Problematic Drug Use Among Outpatients With Schizophrenia and Related Psychoses. Front Psychiatry. 2021;12:762988. doi: 10.3389/fpsyt.2021.762988 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pgph.0005024.ref023] 23.Tumenta T, Oladeji O, Gill M, Khan BA, Olayinka O, Ojimba C, et al. Substance Use Patterns and Schizophrenia Spectrum Disorders: A Retrospective Study of Inpatients at a Community Teaching Hospital. J Clin Med Res. 2020;12(12):803–8. doi: 10.14740/jocmr4380 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pgph.0005024.ref024] 24.Abbasi LN, Daradkeh TK, ElWasify M, Abassy S. Prevalence of substance use among a sample of patients attending an outpatient psychiatric clinic in Amman, Jordan. Discov Ment Health. 2024;4(1):57. doi: 10.1007/s44192-024-00113-1 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pgph.0005024.ref025] 25.Negrete JC. Clinical aspects of substance abuse in persons with schizophrenia. Can J Psychiatry. 2003;48(1):14–21. doi: 10.1177/070674370304800104 [DOI] [PubMed] [Google Scholar]

[pgph.0005024.ref026] 26.Bennett ME, Brown CH, Peer J, Li L, Bellack AS. Patterns and Predictors of Changes in Substance Use in Individuals with Schizophrenia and Affective Disorders. J Dual Diagn. 2012;8(1):2–12. doi: 10.1080/15504263.2012.647466 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pgph.0005024.ref027] 27.Ward HB, Nemeroff CB, Carpenter L, Grzenda A, McDonald WM, Rodriguez CI, et al. Substance use disorders in schizophrenia: Prevalence, etiology, biomarkers, and treatment. Personalized Medicine in Psychiatry. 2023;39–40:100106. doi: 10.1016/j.pmip.2023.100106 [DOI] [Google Scholar]

[pgph.0005024.ref028] 28.Khokhar JY, Dwiel LL, Henricks AM, Doucette WT, Green AI. The link between schizophrenia and substance use disorder: A unifying hypothesis. Schizophr Res. 2018;194:78–85. doi: 10.1016/j.schres.2017.04.016 [DOI] [PMC free article] [PubMed] [Google Scholar]

PERMALINK

Prevalence and factors associated with illicit substance use among persons with Schizophrenia at a Tertiary Referral Hospital in Zambia

Kimberley R Kurehwatira

Emmanuel L Luwaya

Joreen P Povia

Chileleko Siakabanze

Salma M Baines

Emmanuel Yumba

Prince Mulambo

David N Masta

Nestorine N Ngongo

Natasha Chishala

Emmanuel O Riwo

Katongo H Mutengo

Hanzooma Hatwiko

Martin Chakulya

Lukundo Siame

Bislom C Mweene

Sepiso K Masenga

Roles

Abstract

Introduction

Methodology

Ethics statement

Study design

Study setting

Study population

Target population.

Accessible population.

Actual study population

Eligibility and recruitment

Data collection

Assessment of clinical variables

Study variables

Data analysis

Results

Fig 1. Eligibility flow diagram.

Characteristics of the study population

Table 1. Characteristics of the study populations.

Assessment of collinearity between variables

Fig 2. Correlation matrix of variables.

Factors associated with substance use in logistic regression

Table 2. Logistic regression analysis for Substance use.

Discussion

Factors associated with lower odds of illicit substance use in multivariable analysis

Novel correlate: hospitalization frequency

Dissociation of bivariate predictors

Clinical and policy implications

Conclusion

Supporting information

Data Availability

Funding Statement

References

Decision Letter 0

Feten Fekih-Romdhane

Roles

Author response to Decision Letter 1

Decision Letter 1

Feten Fekih-Romdhane

Roles

Author response to Decision Letter 2

Decision Letter 2

Feten Fekih-Romdhane

Roles

Author response to Decision Letter 3

Decision Letter 3

Yatan Pal Singh Balhara

Roles

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

PERMALINK

RESOURCES

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