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. 2024 Oct 4;14(10):e086487. doi: 10.1136/bmjopen-2024-086487

Substance use and risk of suicide among adults who sought mental health and addiction specialty services through a centralised intake process in Nova Scotia: a cross-sectional study

Matiwos Soboka 1,✉, Sherry H Stewart 2, Philip Tibbo 2,3, JianLi Wang 1,2
PMCID: PMC11459331  PMID: 39366714

Abstract

Abstract

Objectives

The objectives of this study are as follows: (1) to estimate the prevalence of suicide risk among individuals seeking mental health and addiction (MHA) services in Nova Scotia; (2) to examine the relationship between substance use and suicide risk among this population.

Setting

MHA intake programme, a province-wide centralised intake process established in 2019 by the Department of Health and Wellness of Nova Scotia.

Participants

We included 22 500 MHA intake clients aged 19–64 years old who contacted MHA intake from 2020 to 2021.

Primary outcome measures

During the intake assessment, clients were assessed for suicide risk (past suicide attempt, suicidal ideation during the interview or 2 weeks before the interview).

Results

The lifetime prevalence of suicide attempt was 25.25% in the MHA clients. The prevalence of mild and moderate/high suicide risk was 34.14% and 4.08%, respectively. Clients who used hallucinogens had the highest prevalence of mild and moderate/high suicide risk (61.3% and 12.9%, respectively), followed by amphetamine/methamphetamine (47.6% and 13.3%, respectively) and sedative/hypnotics (47.2% and 8.9%, respectively) users. Stimulant (aOR=1.84, 95% CI 1.23 to 2.75) and hallucinogen (aOR=3.54, 95% CI 1.96 to 6.43) use were associated with increased odds of moderate/high suicide risk compared with denying current use. Additionally, alcohol (aOR=1.17, 95% CI 1.06 to 1.30) and tobacco (aOR=1.20, 95% CI 1.10 to 1.30) use were associated with increased odds of mild suicide risk.

Conclusion

Suicide behaviours were prevalent among clients seeking MHA services. Substance use is an important factor associated with suicide risk in this population. This result underscored the importance of considering substance use patterns when assessing suicide risk and highlighted the need for targeted interventions and preventive measures for individuals engaging in substance use. Future interventional studies are needed to identify and evaluate effective strategies for reducing substance use and suicide risk among clients of MHA central intake.

Keywords: cross-sectional studies, mental health, anxiety disorders, depression & mood disorders, substance misuse, suicide & self-harm

STRENGTHS AND LIMITATIONS OF THIS STUDY.

  • The strengths of this study included the use of a large sample size and assessing various types of substance use in relation to suicide risk.

  • This study was the first in Canada to examine the association between substance use and suicide risk among clients who sought mental health and addiction services.

  • Due to social desirability bias, some individuals may not disclose substance use and suicidal risk.

  • The temporal relationship between substance use and suicidal risk could not be established due to the nature of our study design.

Introduction

Suicide is a major global public health problem, resulting in the loss of over 700 000 lives annually worldwide.1 In Canada, suicide ranks among the top 10 causes of death,2 claiming approximately 4500 lives each year, equivalent to an average of 12 deaths per day. Additionally, suicide is the second leading cause of death among individuals aged 15–34 years in Canada.2 3 As of 2023, according to the WHO, the suicide rate in Canada is 11.8 per 100 000 individuals, with rates of 17.6 per 100 000 in males and 6.1 per 100 000 in females.4 In Canada, despite prevention and treatment efforts, the prevalence of suicide has risen from 2.7% before the pandemic to 4.2% during the COVID-19 pandemic.5

Substance use, alongside depression, is a significant risk factor for suicidal ideation, attempts and completed suicide.6,9 Additionally, frequent and prolonged substance use often results in substance use disorder (SUD), which is characterised by compulsive use, significant impairment or distress, negative effects on health and daily life10 and a notably amplified risk of suicide.11 In psychological autopsy studies, 19%–63% of all suicides have been associated with SUDs, primarily alcohol use disorder.9 Recent systematic reviews and meta-analyses showed that SUD had a significant association with suicidal behaviours.11 12 Also, studies have indicated that use of substances such as alcohol, tobacco, cannabis, cocaine, opioid, stimulants, inhalants, hallucinogens and hypnotic medications are related to a higher risk of suicide compared with abstaining from these substances.711 13,18 This could be due to the harmful consequences of substance use on critical cognitive functions, such as judgement, decision making and self-control, as well as its disruptive impact on neurotransmitter pathways, ultimately increasing vulnerability to suicidal behaviours.6 19 Additionally, substance use may increase the risk of developing or worsening mental health problems such as depression, anxiety, post-traumatic stress disorder, bipolar disorder and psychosis, thereby significantly heightening the risk of suicide. Also, individuals with mental health problems might use substances as coping strategy, which may contribute to a higher risk of suicide.1220,25 Moreover, frequent substance use has associations with challenges such as financial hardship unemployment, homelessness, social isolation and lack of family support. These challenges are associated with higher stress levels, which, in turn, may increase risk of suicide.17 26 While studies have shown the relationship between alcohol, tobacco, cannabis, cocaine, opioid, stimulant, sedative or hypnotic use and suicidal behaviours,1127,29 there remains a gap in our understanding of how this relationship varies when individuals have symptoms of unconfirmed mental health problems.

In Canada, alcohol use contributes to approximately 25% of suicide deaths,29 whereas 22% of suicides are attributed to opioid toxicity.30 A study conducted in Canada revealed that increasing one’s cannabis use during the COVID-19 pandemic was associated with a 1.97 times increased risk for suicidal ideation.21

However, in Canada, existing studies focused primarily on alcohol use and suicide, while only a few have examined the relationship between illicit substance use and suicide.29 31 Also, these studies have primarily focused on adolescents and specific genders.7 31 32 Additionally, the relationship between substance use and suicidal behaviours was not well studied among preclinical populations. Nova Scotia is the province with the highest prevalence of substance use, with an estimated rate of approximately 14%, surpassing the national average of 11.0%.33 To enhance the MHA services access, Nova Scotia established a centralised MHA intake process in 2019, which is open to all residents in the province. This centralised intake system is the first of its kind in Canada. Exploring the relationship between substance use and suicidal behaviours among preclinical population holds paramount importance in the context of population health and mental health services planning. By examining this relationship at an early stage, we may be able to identify individuals who are more likely to report suicide. This knowledge can inform the development and implementation of targeted preventive and intervention strategies, which not only reduce the likelihood of substance use and related suicide risk but also address underlying mental health concerns. Such studies also inform policy decisions aimed at reducing substance use and suicide rates, thereby promoting the well-being of the broader population. The objectives of this study are as follows: (1) to estimate the prevalence of suicide risk among MHA intake users aged 19–64 years old; (2) to examine the relationship between each type of substance use and suicide risk among MHA intake users aged 19–64 years old.

Methods

Study settings, design and data collection

This cross-sectional study used the data collected by the Mental Health and Addiction (MHA) intake programme from January 2020 to December 2021. The MHA intake established in 2019 is the entry point to MHA services in Nova Scotia. The MHA intake covers the population of all ages across four health zones (Northern, Eastern, Western and Central) in Nova Scotia.

For this study, 22 500 MHA clients aged 19–64 years old were included. In Nova Scotia, individuals younger than 19 years old, especially those who live in the area of Halifax municipality area, may directly contact the IWK (children’s care center) for mental health services. Additionally, several specialty programmes, including geriatric psychiatry, eating disorders and early psychosis intervention may take physician referrals or self-referrals without MHA intake assessment. These two subpopulations may not go through the MHA intake. Client screening was conducted by trained clinical therapists, social workers and registered nurses. These clinicians interview clients by telephone or sometimes in person using a semistructured interview, informed by the MHA Intake Triage Assessment with embedded Triage Acuity Guide. Prior to data collection, interviewers were given 3 weeks of training and orientation. The intake assessment interview included demographics, presenting concerns/symptoms, substance use, suicide risk, life stressors, current and past diagnoses, mental and physical health problems and medication use and barriers to service access.34 Given the large number of clients in the database and vast area where they lived, obtaining informed consent from each client was not feasible. This study was a secondary data analysis using existing deidentified data. Ethical approval for the MHA intake was received from the Research Ethics Board of the Nova Scotia Health (NSH) Authority.

Variables and measures

Outcome variable

Suicide risk

In this study, suicide risk includes past suicide attempts, suicidal thoughts 2 weeks before the interview, and suicidal ideation during the interview. During the assessment, clients were asked the following questions: ‘Have you had thoughts about suicide or wanting to be dead in the past two weeks?’; ‘Have you tried to kill yourself or attempt suicide in the past?’ and ‘Do you have thoughts of suicide now?’ Clients who answered ‘yes’ to one of the questions were assessed further for suicide risk, and the interviewers classified the client into low, moderate or high suicide risk levels based on clinical judgement and the suicide risk assessment and intervention tool (SRAI). The SRAI includes risk profile/indicators such as suicide ideation, suicidal intent or lethal plan, recent suicide attempt, past suicide attempt, hopelessness, intense emotions, rage, anger, agitation, humiliation, severe anxiety, panic attack, current alcohol or substance use, withdrawing from family and friends, poor reasoning/judgement, recent mood change, recent crisis/conflict/loss, ethnic or cultural risk group or refugee, family history of suicide, trauma such as domestic violence/sexual abuse/neglect, poor self-control, mental illness or addiction, depression/anhedonia, psychotic, command hallucinations, recent admission/discharge/emergency department visit, chronic medical illnesses/pain, disability/impairment, collateral information supports suicide intent, clinical intuition, lack of family/friends support and caregiver unavailable. The suicide risk (low, moderate and high) assessment was based on clinical judgement by trained clinicians based on the above collected risk indicators, not on the number of items checked. These items were provided to support the clinical decision to categorise the risk of suicide as low, moderate and high risk.34 35 Due to the low number of observations for high suicide risk, we merged it with the moderate risk category.

Exposure

Substance use

Substance use was the primary covariate of interest. This study assessed the following substances: alcohol, hallucinogens (ketamine, lysergic acid diethylamide, mescaline (peyote cactus), phencyclidine and/or psilocybin (mushrooms)), inhalants, opioids, sedatives/hypnotics, stimulants (amphetamine, methamphetamine, crack cocaine, powder cocaine, Dexedrine (Adderall), ecstasy (MDMA) and/or methylphenidate (Conerta/Ritalin), tobacco and other substances. Clients were asked if they were using any of the above substances using a ‘Yes’ or ‘No’ question. Those who answered ‘Yes’ to any substances were assessed further for specific substance, frequency (2–4 times a month, 2–3 times a week, 4 or more times a week and daily), route of administration (oral, intravenous, inhaling, intramuscular, subcutaneous, smoking, snorting, transdermal patch and rectal), duration, last use and impact on functionality.

Polysubstance use

In this study, polysubstance use was defined as using two or more of the above substances.

Covariates

Demographic and socioeconomic information

This includes age (19–29, 30–39, 40–49, 50–64), gender (women, men, non-binary and did not specify), marital status (married, common-law partnership, single, separated, divorced and widowed), income sources (employment, employment insurance, pension, social assistance, disability, spouse, partner, others (none), ethnicity (White, Indigenous, Black, Asian, Other, Declined), living conditions (private home/apartment/rented room, board and care, assisted living, hospital, group home, homeless, hotel, hostel, motel and jail transition house), access to employee assistance programmes or private insurance and health zones. The MHA intake did not collect data about biological sex.

Presence and frequency of psychiatric symptoms

Clients were assessed for experiencing mental health symptoms, including the frequency of the symptoms and the impact of the symptoms on functionality over the past month. The symptom domains included mood, anxiety, psychosis, trauma, cognition, behaviours and general (eg, eating, dieting and sleep). For each domain, the client may answer ‘yes’ or ‘no’ for the presence of the symptom. If clients answered ‘yes’, questions about the frequency were asked. The interviewer chose the overall impact on functionality as mild, moderate or severe based on the frequency of the symptoms and clinical judgement. For this analysis, we included symptom domains with ‘yes’ and ‘no’ answers.

Psychosocial stressors

Clients were assessed if they encountered psychosocial stressors and how these stressors affected their functioning.34 The psychosocial stressors included childhood adversity, current abuse, economic/finances, education/school, ethnic/cultural factors, family and significant relationships, housing, legal issues, leisure/recreation, military parent/guardian–child conflict, past trauma, physical health/disability, social relationships spiritual/religious beliefs. In this analysis, we classified psychosocial stressors into three categories: ‘0’, indicating the absence of any such stressor; ‘1’, indicating the experience of one stressor and ‘2’, indicating two or more psychosocial stressors.

Presence of current or history of medical problems

Clients were interviewed for the presence of current/past medical illnesses such as brain injury, concussion, seizure, stroke, chronic pain, fibromyalgia, obesity, dyslipidaemia, hypertension, heart disease, hyperthyroid, kidney disease, liver disease, cancer, respiratory disease, diabetes, menstrual-related disorder, haematologic disease and other. For this analysis, we grouped the presence of current or history of medical problems into three categories: ‘0’ for no physical health problems, ‘1’ for having one provisional diagnosis of current/past medical illnesses and ‘2’ for having two or more provisional diagnosis of current/past medical illnesses.

Data analysis

Multivariate Imputation by Chained Equations was used to impute variables with missing values.36 37 We excluded the quantity of substance used and other variables with large missing values. Only variables with missing values of 20% and less were imputed. Considering the average of missing values percentage in our study, we used five imputations with a maximum iteration of 20. The analysis was conducted using the combined data sets based on Rubin’s rules.38 Sociodemographic characteristics and symptoms of mental health problems were described using descriptive statistics. We categorised specific substances into groups, namely alcohol, opioids, stimulants, cannabis, hallucinogens, sedatives/hypnotics, tobacco and polysubstance, to reduce the complexity of the analysis and increase the interpretability of the results. The frequency of each substance use was calculated by aggregating the frequency of each specific substance. For instance, the frequency of beer, wine and other types of alcohol was aggregated to yield one variable named ‘frequency of alcohol use’. Then, we recategorised the frequency of each substance into occasional use (2–4 times a month), frequent use (2–3 times a week and four or more times a week) and daily use. For objective 1, we calculated the proportions of individuals at different suicide risk levels. Also, we compared the proportions of suicide risk levels by substance use, and χ2 tests were performed to compare the differences. Multinomial logistic regression modelling was used to examine the association between substance use and suicide risk levels, adjusting for sociodemographic characteristics, health regions, gambling, symptom domains of mood, anxiety, trauma, psychosis, cognitive, current/past medical illnesses and psychosocial stressors. The pooled adjusted ORs and corresponding 95% CI were used to estimate the strength of the associations. The analysis was performed using R software (V.4.2.3).

Results

Sociodemographic characteristics

Of the total of 22 500 clients who were included in this study, 6451 were men, 8798 were women, 186 were non-binary and 7065 did not specify their gender. The mean age of the clients was 37.09, with age ranging from 19 to 64. About 4% of the clients were Indigenous and about 60.3% were White Ethnicity/Race.

Magnitude of suicide risk

Among the total clients, 25.25% (n=5682) reported a lifetime prevalence of suicide attempts. Also, among the clients, 34.55% (n=7774) had suicidal ideation within 2 weeks before the interview. About 34.14% (n=7682) clients were determined to be at mild suicidal risk and 4.08% (n=917) were at moderate/high risk of suicide. The proportions of mild and moderate/high suicide risk by demographic characteristics are presented in table 1.

Table 1. Suicidal risk level by sociodemographic characteristics among patients aged 19–64 who were assessed by the Nova Scotia Mental Health and Addiction intake in 2020 and 2021 (n=22 500).

Variables Suicide risk
No risk, N (%) Mild, N (%) Moderate/high risk, N (%) X2 P value
Gender Female 5453 (61.98) 3068 (34.87) 277 (3.15) 102.77 <0.001
Male 4204 (65.17) 1942 (30.1) 305 (4.73)
Non-binary/did not specify 4244 (58.53) 2672 (36.85) 335 (4.62)
Ethnicity/race White 8102 (59.75) 5012 (36.96) 445 (3.28) 194.92 <0.001
Indigenous 525 (60.76) 303 (35.07) 36 (4.17)
Others 616 (61.05) 358 (35.48) 35 (3.47)
Declined 4658 (65.9) 2009 (28.42) 401 (5.67)
Age groups 19–29 years old 4353 (54.44) 3248 (40.62) 395 (4.94) 294.15 <0.001
30–49 years old 6332 (65.04) 3063 (31.46) 340 (3.49)
50–64 years old 3216 (67.44) 1371 (28.75) 182 (3.82)
Marital status Married/common-law/partnership 7360 (64.44) 3696 (32.36) 365 (3.2) 122.46 <0.001
Single 4486 (57.4) 2922 (37.39) 407 (5.21)
Separated/divorced/widowed 2055 (62.96) 1064 (32.6) 145 (4.44)
Income sources Employment 6343 (63.77) 3257 (32.74) 347 (3.49) 61.22 <0.001
Employment insurance/pension 2375 (61.99) 1291 (33.7) 165 (4.31)
Social assistance/disability 2710 (60.84) 1544 (34.67) 200 (4.49)
Spouse/partner 389 (60.03) 237 (36.57) 22 (3.4)
Others* 874 (56.13) 611 (39.24) 72 (4.62)
None 1210 (58.65) 742 (35.97) 111 (5.38)
Living status Private home/apartment/rented room 13 312 (62.18) 7250 (33.86) 847 (3.96) 44.61 <0.001
Board and care/assisted living/group home 266 (57.58) 174 (37.66) 22 (4.76)
Homeless/others 323 (51.35) 258 (41.02) 48 (7.63)
Access to EAP/private insurance No 6446 (64.81) 3099 (31.16) 401 (4.03) 73.02 0.001
Yes 7455 (59.38) 4583 (36.51) 516 (4.11)
Health regions Central 6118 (58.28) 4203 (40.04) 176 (1.68) 992.52 <0.001
Eastern 3433 (75.88) 772 (17.06) 319 (7.05)
Northern 2413 (59.14) 1470 (36.03) 197 (4.83)
Western 1937 (56.99) 1237 (36.39) 225 (6.62)
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*

Other income: Child Tax Benefit, Worker’s Compensation Board (WCB), WCB, Ssavings, Canada Emergency Response Benefit (CERB), Pparents, family, Sstudent loans, spouse, none .

EAPemployee assistance programmes

Amphetamine/methamphetamine users were more likely to be at moderate to high suicidal risk compared with non-users (13.30% vs 3.98%, p-value<0.001). Also, individuals who engage in hallucinogen use were more likely to be at both mild (61.29% vs 33.95%, p-value<0.001) and moderate to high (12.90% vs 4.01%, p-value<0.001) suicide risk than non-users. Sedative/hypnotics users were more likely to report both mild (47.15% vs 34.0) and moderate/high suicide risk (8.94% vs 4.02%) compared with non-users (see table 2). The prevalence of suicide among daily amphetamine/methamphetamine users was high, with 53.28% experiencing mild suicidal ideation and 12.3% experiencing moderate/high suicidal ideation (see table 3).

Table 2. Proportions of suicidal risk level by substance use and mental health problems among patients aged 19–64 who were assessed by the Nova Scotia Mental Health and Addiction intake in 2020 and 2021 (n=22 500).

Variables Suicide risk
No risk, N (%) Mild, N (%) Moderate/high risk, N (%) X2 P value
Alcohol No 7673 (64.69) 3742 (31.55) 446 (3.76) 88.89 <0.001
Yes 6228 (58.54) 3940 (37.03) 471 (4.43)
Opioid No 13 286 (61.69) 7385 (34.29) 866 (4.02) 7.59 <0.02
Yes 615 (63.86) 297 (30.84) 51 (5.3)
Amphetamine/methamphetamine No 13 810 (62.02) 7571 (34) 886 (3.98) 81.45 <0.001
Yes 91 (39.06) 111 (47.64) 31 (13.3)
Cocaine No 12 853 (62.63) 6870 (33.48) 799 (3.89) 76.51 <0.001
Yes 1048 (52.98) 812 (41.05) 118 (5.97)
Cannabis No 9557 (68.89) 3817 (27.52) 498 (3.59) 782.32 <0.001
Yes 4344 (50.35) 3865 (44.8) 419 (4.86)
Hallucinogen No 13 861 (62.03) 7587 (33.95) 897 (4.01) 96.23 <0.001
Yes 40 (25.81) 95 (61.29) 20 (12.9)
Sedatives/hypnotics No 13 793 (61.98) 7566 (34) 895 (4.02) 36.66 <0.001
Yes 108 (43.9) 116 (47.15) 22 (8.94)
Tobacco No 7854 (62.75) 4167 (33.29) 496 (3.96) 11.12 0.004
Yes 6047 (60.57) 3515 (35.21) 421 (4.22)
Poly substance No 8529 (68.12) 3556 (28.4) 435 (3.47) 481.07 <0.001
Yes 5372 (53.83) 4126 (41.34) 482 (4.83)
Mood symptoms No 3973 (84.84) 675 (14.41) 35 (0.75) 1343.7 <0.001
Yes 9928 (55.72) 7007 (39.33) 882 (4.95)
Anxiety symptoms No 3377 (79.68) 776 (18.31) 85 (2.01) 709.05 <0.001
Yes 10 524 (57.63) 6906 (37.82) 832 (4.56)
Trauma symptoms No 6627 (69.93) 2573 (27.15) 277 (2.92) 463.67 <0.001
Yes 7274 (55.86) 5109 (39.23) 640 (4.91)
Psychosis symptoms No 11 804 (63.59) 6107 (32.9) 653 (3.52) 185.12 <0.001
Yes 2097 (53.28) 1575 (40.02) 264 (6.71)
Cognitive symptoms No 7275 (68.59) 2981 (28.1) 351 (3.31) 393.6 <0.001
Yes 6626 (55.71) 4701 (39.53) 566 (4.76)
Current/past medical illnesses 0 10 415 (62.53) 5570 (33.44) 672 (4.03) 18.57 <0.001
1 2463 (60.26) 1448 (35.43) 176 (4.31)
2+ 1023 (58.26) 664 (37.81) 69 (3.93)
Psychosocial stressors 0 4816 (74.26) 1471 (22.68) 198 (3.05) 865.44 <0.001
1 3199 (66.18) 1463 (30.26) 172 (3.56)
2+ 5886 (52.64) 4748 (42.46) 547 (4.89)
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Table 3. The proportions of suicide risk by frequencies of various substance use.

Frequency of substance use Suicide risk
No risk, N (%) Mild, N (%) Moderate/high risk, N (%) X2 P value
Alcohol
 Occasional use 1456 (53.69) 1137 (41.92) 119 (4.39) 155.14 <0.001
 Frequent use 1027 (55.12) 745 (40.00) 91 (4.88)
 Daily use 1647 (60.84) 928 (34.28) 132 (4.87)
Opioid
 Occasional/frequent use 100 (54.95) 71 (39.01) 11 (6.04) 10.62 <0.03
 Daily 417 (65.46) 189 (29.67) 31 (4.87)
Amphetamine/methamphetamine
 Occasional/frequent use 34 (44.16) 31 (40.26) 12 (15.58) 78.48 <0.001
 Daily 42 (34.43) 65 (53.28) 15 (12.3)
Cocaine
 Occasional use 194 (50.92) 161 (42.26) 26 (6.82) 64.31 <0.001
 Frequent use 249 (50.40) 219 (44.33) 26 (5.26)
 Daily use 474 (56.29) 325 (38.60) 43 (5.11)
Cannabis
 Occasional use 1052 (52.44) 855 (42.62) 99 (4.94) 795.08 <0.001
 Frequent use 682 (54.82) 513 (41.24) 49 (3.93)
 Daily use 2504 (48.27) 2421 (46.67) 262 (5.05)
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Factors associated with suicide risk

Controlling for the effects of sociodemographic variables, symptoms of mental health problems, current/past medical illnesses, psychosocial stressors and gambling, multinomial logistic regression showed that, alcohol use was significantly associated with increased odds of mild suicide risk (aOR=1.17, 95% CI 1.06 to 1.30), whereas daily use of alcohol associated with higher odds of moderate to high suicide risk (aOR=1.34, 95% CI 1.02 to 1.77) compared with denying current use of alcohol. Compared with denying current use, stimulant use was associated with higher odds of mild (aOR=1.52, 95% CI 1.22 to 1.89) and moderate to high (aOR=1.84, 95% CI 1.23 to 2.75) suicide risk. Additionally, hallucinogen use was associated with increased odds of mild (aOR=2.04, 95% CI 1.38 to 3.03) and moderate to high (aOR=3.54, 95% CI 1.96 to 6.43) suicide risk. Similarly, individuals using sedatives/hypnotics had about two times higher odds of moderate/high suicide risk than their non-user (aOR=1.90, 95% CI 1.112 to 3.22). Tobacco use was associated with higher odds of mild suicide risk (aOR=1.20, 95% CI 1.10 to 1.30) compared with denying current use of tobacco. However, cannabis use, polysubstance use and frequency of cocaine and cannabis were not associated with mild and moderate/high suicide risk (see table 4).

Table 4. The results of multinomial logistic regression on the associations between substance use and suicide (n=22 500).

Variables Suicide risk
Mild Moderate/high risk
aOR (95% CI) aOR (95% CI)
Alcohol No Reference
Yes 1.17 (1.06 to 1.30) 1.16 (0.91 to 1.47)
Stimulants No Reference
Yes 1.52 (1.22 to 1.89) 1.84 (1.23 to 2.75)
Tobacco use No Reference
Yes 1.20 (1.10 to 1.30) 1.09 (0.90 to 1.33)
Hallucinogen No Reference
Yes 2.04 (1.38 to 3.03) 3.54 (1.96 to 6.43)
Sedatives/hypnotics No Reference
Yes 1.25 (0.92 to 1.69) 1.90 (1.12 to 3.22)
Frequency of alcohol use Denying current use Reference
Occasional use 0.97 (0.86 to 1.09) 0.88 (0.67 to 1.16)
Frequent use 0.97 (0.85 to 1.11) 1.27 (0.94 to 1.71)
Daily use 1.06 (0.93 to 1.20) 1.34 (1.02 to 1.77)
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Discussion

The MHA intake data showed that suicide behaviours were prevalent in the MHA intake clients. About one-third reported suicide ideation within the past 2 weeks before the interview; over 34% were determined to have mild suicide risk and 4.1% had moderate or high suicide risk. Use of various substances use such as alcohol, tobacco, stimulants, hallucinogens and sedatives/hypnotics use were associated with an increased risk of suicide. This association remained significant even after adjusting for factors that may elevate suicide risk.

In our study, about one-third (34.6%) of clients reported experiencing suicidal ideation. The observed high prevalence of suicide ideation in our study may be attributed to several factors. For instance, individuals with mental health problems may turn to substance use as a self-medication for symptoms of depression, anxiety and bipolar disorder or as a coping mechanism for dealing with traumatic experiences.39,41 Also, individuals with mental illnesses may use substances to acutely cope with distress and suicidal ideation (eg, in attempts to improve mood or block ruminative thinking).42,45 However, depending on factors such as dose and chronicity, substance use can actually worsen symptoms of mental health problems, heightening suicidal ideation by amplifying distress and impairing decision making and judgement.10 Trauma experience may also act as a third variable contributing to the association between substance use and suicide, as trauma often leads to psychological distress, suicidality and substance use as a coping mechanism.46,48 The complex relationships between substance use, suicide and mental health problems are highlighted in this study, and warrant further investigation. The observed prevalence of suicidal ideation in our study may be due to the psychological impact of the COVID-19 pandemic on the clients. It is important to note that the prevalence of suicidal ideation in our study was higher than the prevalence of suicidal ideation reported during the COVID-29 pandemic in Nova Scotia (13.6%)49 and Prince Edward Island (25%).49 This disparity may be attributed to the difference in the study population, as our study focused on individuals seeking mental health and SUD treatment services, who are known to be more susceptible to suicide risk compared with the general population.50 51

In our study, daily alcohol use was associated with an increased risk of moderate/high suicide risk, consistent with a meta-analysis done by Darvishi et al.27 Several factors may contribute to this association; for instance, alcohol use disorder can lead to depressive symptoms or exacerbate underlying mental health conditions and ultimately increase suicide risk.52 53 About 80% of clients in our study reported experiencing symptoms of depression and anxiety, and the comorbidity between substance use such as alcohol and mental health problems could potentially contribute to the observed association with suicide risk. Moreover, chronic alcohol use may lead to social and interpersonal problems, further contributing to feelings of hopelessness and despair, thereby increasing the risk of suicide. Additionally, individuals with suicidal ideation may turn to alcohol to get relief from stress related to suicidality.52 54 Furthermore, the association between alcohol use and suicide can be explained by the increased risk of attempting suicide under the influence of alcohol intoxication.55

The prevalence of moderate/high suicidal risk among amphetamine/methamphetamine users in our study (13.3%) was in line with a systematic review done by Mantinieks et al (9.3%).56 Consistent with previous studies,57 58 our study found that stimulant use was associated with an increased risk of suicide (mild and moderate/high suicide risk). The observed association may be attributed to the stimulant effects of this substance, which may lead to mood swings, agitation and even psychosis, thereby contributing to increased suicide risk. Additionally, chronic stimulant use can disrupt sleep patterns and worsen the underlying symptoms of mental health problems such as depression or bipolar disorder, which are known risk factors for suicide.59,61 Furthermore, sleep deprivation resulting from stimulant use may directly intensify the risk of suicide, as there is a well-established relationship between insomnia and an increased risk of suicidal ideation.62 Conversely, studies indicated that individuals with attention deficit hyperactivity disorder (ADHD) who used prescription stimulants had a lower risk of suicide.63 64 Individuals with diagnosed ADHD or undiagnosed ADHD may use illicit amphetamine as a form of self-treatment, but further investigation is needed to understand this relationship among individuals seeking mental and addiction services.

Sedatives/hypnotics are commonly prescribed for sleep and anxiety disorders. While these medications are generally considered safe when used as prescribed, misuse or long-term use can increase the risk of suicide. For instance, in our study, this substance was associated with increased suicidal risk, which is consistent with previous studies.2065,67 Although the relationship between sedatives/hypnotics and suicide risk is controversial, some Z-drugs (zolpidem, zaleplon and eszopiclone) were reported to increase suicidal behaviour.15 The association between suicide risk and sedatives/hypnotics may be explained by prolonged exposure to these substances and withdrawal symptoms following abrupt discontinuation of these medications, contributing to increased susceptibility to suicide risk.66 68 Also, individuals with a high risk of suicide may use sedatives/hypnotics in an attempt to self-treat or alleviate symptoms associated with underlying mental health problems, including suicidal ideation, which may elucidate the observed association. Moreover, using other substances may also contribute to the association between sedatives/hypnotics use and suicide risk. Further investigation is needed to understand the mechanisms of how sedatives/hypnotics increase suicide risk.

Consistent with the study conducted in the USA,14 we found that hallucinogen use was most strongly associated with increased suicide risk (mild and moderate/high suicide risk) among the substances examined, contradicting studies that demonstrated a reduction in suicide risk with hallucinogen use.69,71 The association between hallucinogens and suicide risk is controversial, with some studies suggesting that hallucinogens, particularly psilocybin (magic mushrooms), decrease the risk of suicide and mental health problems, while others indicate an increase.70,72 Although some individuals may use hallucinogens as a self-treatment for mental health problems, it is important to note that individuals with a pre-existing vulnerability to psychosis or unstable mental health may experience adverse reactions to hallucinogens, thereby potentially increasing the risk of suicide. Also, hallucinogens can cause perceptual disturbances that potentially increase stress levels, which may increase the risk of suicide.73 74 Furthermore, it is imperative to note that individuals who use hallucinogens may also indulge in concurrent illicit drug use, which may amplify the risk of suicide. However, further investigation is needed to understand the temporal relationship between hallucinogen use and suicide risk.

Our finding showed that cannabis, cocaine, opioid and polysubstance use were not associated with suicide risk, which is an unexpected result. This is surprising given that previous studies showed opioid use,75 76 polysubstance use,77 cannabis78 and cocaine79 use were associated with suicidal ideation. The difference between our study and previous studies may be related to the tool used to assess substances and study design. For instance, we measured opioid use based on self-report, while studies conducted in the USA used the Connecticut All-Payer Claims Database (APCD)76 and DSM-IV75 to assess opioid use. Also, while studies conducted in the USA used ICD-10,76 and self-report75 to assess suicide risk, we did not use standardised tools but our data collectors assessed suicide risk based on clinical knowledge guided by a checklist (SRAI). The difference regarding the association between cannabis use and suicide risk in our study and the previous study may be related to the nature of study designs (cross-sectional vs longitudinal study).78 Also, the study conducted in the USA78 did not categorise suicide risk as low versus moderate/high as we did in our study; instead they assessed suicidal ideation and baseline suicide attempt. These methodological and design differences may have contributed to the different results in our study versus the study conducted in the USA. The lack of association between suicide risk and cannabis, cocaine, opioid and polysubstance use in our study, contrary to some previous evidence, highlights the need for continued investigation to understand the complex relationship between substance use patterns and their links with suicide, particularly among individuals in the early stage of seeking MHA services. Longitudinal studies are needed to understand the temporal association between these substances and suicide risk among individuals who are seeking MHA services. Also, further studies are needed by stratifying suicide risk by frequency and amount of cannabis use, cocaine, and opioid use.

The findings from our study can inform the healthcare system in terms of prevention, screening and management of suicidal risk among individuals seeking treatment for substance use and mental health problems. By gaining a more comprehensive understanding of the relationship between substance use and suicidal risk, we can take significant steps towards effectively addressing this issue and improving public health outcomes. The healthcare system can better address suicide risk among individuals seeking MHA services by implementing proactive measures such as early screening of suicide risk and addressing the underlying factors such as substance use, mental health problems and trauma experience, and devising effective prevention and intervention strategies. Also, screening of suicide risk among individuals seeking mental and addiction services is imperative for monitoring suicide risk and providing personalised and comprehensive treatment. Moreover, the health system may consider the integration of screening for suicide among individuals identified with substance use in other settings such as emergency department or primary care.

Strengths and limitations

The strengths of this study include a large sample size and assessing various kinds of substance use in relation to suicide risk. This study is the first to examine the association between substance use and suicide risk controlling for mental health problems among clients who sought MHA services. Also, we did not use DSM-5 criteria or standard tools to collect data regarding SUD, suicide risk level and mental health problems because the goal of the MHA intake is to understand client concerns and to match them to the appropriate level of MHA services; the intake assessment is not to make a diagnosis. Further studies are needed using validated instruments based on DSM-criteria. Additionally, we did not collect data regarding past substance use, and future study is needed to understand the relationship between past substance use and suicide risk. Also, data regarding vaping was not collected in our study. Excluding the quantity of substance use in this study due to a large number of missing values is considered an important limitation. Because this omission hinders our understanding of how varying amounts of substance use may influence suicide risk. Another limitation can be social desirability bias, as some individuals may not disclose substance use and suicidal risk. The findings of this study may not be generalised to all Canadians. Also, individuals who had completed suicide were not represented in this study. Moreover, it is difficult to understand the temporal relationship between substance use and suicidal risk due to the cross-sectional nature of our study design.

Conclusions

There was a high prevalence of suicide behaviours among individuals who were seeking MHA services. Also, this study showed that using substances such as alcohol, tobacco, stimulants, sedatives and hallucinogens were associated with suicide risk. Health professionals need to be aware of these associations and provide comprehensive assessments and support to individuals struggling with substance use and suicide risk, addressing both underlying mental health conditions and substance use. Also, our findings highlighted the association between sedatives/hypnotics and suicide risk, emphasising the need for vigilance and comprehensive screening for individuals undergoing treatment with these medications. Our findings underscore the importance of regular screening for suicide risk among clients seeking MHA treatment services. Furthermore, our findings imply the need for targeted interventions and preventive measures for individuals engaging in substance use. Further studies are needed to understand the temporal relationship between substance use and suicide; particularly, it is essential to investigate the association between sedatives/hypnotics as well as hallucinogens and suicide risk.

Acknowledgements

We would like to thank Nova Scotia Health (NSH) for allowing us to access these data.

Footnotes

Funding: The funding for this study was provided by the CIHR Canada Research Chair (Tier 1) on Health Data Science and Innovation award and a Research Nova Scotia operating grant #2022-2323 to JLW. SHS is supported through a CIHR Tier 1 Canada Research Chair in Addiction & Mental Health.The funder had no role in the study design, data collection, analyses, writing, or dissemination of the findings.

Prepublication history for this paper is available online. To view these files, please visit the journal online (https://doi.org/10.1136/bmjopen-2024-086487).

Data availability free text: The findings of this study rely on data owned by the NSH Authority, and thus, access may be granted, subject to approval from the data custodian.

Patient consent for publication: Not applicable.

Provenance and peer review: Not commissioned; externally peer reviewed.

Patient and public involvement: Patients and/or the public were not involved in the design, or conduct, or reporting or dissemination plans of this research.

Ethics approval: The Research Ethics Board of the NSH Authority approved this study.

Contributor Information

Matiwos Soboka, Email: matiwos2004@yahoo.com.

Sherry H Stewart, Email: Sherry.Stewart@Dal.Ca.

Philip Tibbo, Email: phil.tibbo@nshealth.ca.

JianLi Wang, Email: jianli.wang@dal.ca.

Data availability statement

Data may be obtained from a third party and are not publicly available.

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