Elsevier

Drug and Alcohol Dependence

Volume 76, Supplement, 7 December 2004, Pages S11-S19
Drug and Alcohol Dependence

Association of alcohol and drug use disorders and completed suicide: an empirical review of cohort studies

https://doi.org/10.1016/j.drugalcdep.2004.08.003Get rights and content

Abstract

Background:

This study updated and expanded upon Harris and Barraclough's empirical review [Harris, E.C., Barraclough, B., 1997. Suicide as an outcome for mental disorders. A meta-analysis, Br. J. Psychiatry 170, 205–228] of retrospective and prospective cohort studies of alcohol and drug use disorders and suicide.

Method:

Studies presenting data on alcohol and drug use disorders and suicide originally identified by Harris and Barraclough were used in this study. To find additional studies, (1) the location of English language reports on MEDLINE (1994–2002) were identified with the search terms ‘substance-disorders’ with ‘mortality’ and ‘follow-up’, (2) read throughs were conducted of four prominent alcohol and drug specialty journals from 1966 through 2002, and (3) the reference sections of studies that met criteria were searched for additional reports. This strategy yielded 42 new studies meeting eligibility criteria.

Results:

The estimated standardized mortality ratios (SMR; 95% confidence interval) for suicide were as follows: alcohol use disorder (979; 95% CI 898–1065; p < 0.001), opioid use disorder (1351; 95% CI 1047–1715; p < 0.001), intravenous drug use (1373; 95% CI 1029–1796; p < 0.001), mixed drug use (1685; 95% CI 1473–1920; p < 0.001), heavy drinking (351; 95% CI 251–478; p < 0.001). SMR estimates stratified by sex were also calculated.

Conclusions:

Additional studies on the association of suicide and mixed drug use, heavy drinking, and alcohol use disorders in women augmented the findings of Harris and Barraclough, along with a novel estimate for intravenous drug use, a byproduct of intensive research on HIV in the past decade. There is a large empirical literature on alcohol use disorders and suicide and a moderate literature on suicide and opioid use disorders and IV drug use. There remains limited prospective data on the association of suicide and other drug use disorders (e.g., cocaine, cannabis).

Introduction

Evidence for an association of suicide with alcohol and drug use disorders is based largely upon retrospective and prospective cohort studies and postmortem “psychological autopsy” studies. Empirical reviews of cohort studies (Harris and Barraclough, 1997) and psychological autopsy studies (Cavanagh et al., 2003) have demonstrated that alcohol and drug use disorders are strongly associated with suicide. However, given limited sample sizes, psychological autopsy studies have typically combined drug use disorders into a single broad category (e.g., Lesage et al., 1994). As a result, psychological autopsy studies have provided little data on the association of specific drug use disorders and suicide, with the exception of alcohol. Harris and Barraclough's empirical review of cohort studies containing data on alcohol and drug use disorders and suicide consisted primarily of reports on alcohol use disorders and, to a lesser extent, opioid use disorders. The magnitude of the association of other drug use disorders (e.g., cannabis, cocaine) and suicide based on cohort studies is unclear.

Suicide research has predominantly been conducted in western, industrialized countries where women have lower rates of suicide and a lower prevalence of alcohol and drug use disorders, contributing to small subsamples of women with drug use disorders in suicide studies. The tendency of many earlier studies of alcohol and drug misuse to exclude women also has contributed to a dearth of knowledge. Murphy (1998) reviewed sex differences in alcoholism in American and European studies and found that sex differences were inconsistent. Some (Harris and Barraclough, 1997) but not all evidence (Conner et al., 2003a) suggests that sex moderates the association of alcohol use disorders and suicide. However, there are meager data on this issue with regard to other drug use disorders.

This study updates and augments the empirical review by Harris and Barraclough of retrospective and prospective cohort investigations that have provided estimates of the suicide risk (standardized mortality ratios, SMRs) associated with specific alcohol and drug use disorders. Harris and Barraclough's review covered studies identified through 1993 (using a MEDLINE search) and through mid-1995 (using read throughs of predominantly psychiatry journals). There have been several reports published since that time, necessitating an update. Moreover, Harris and Barraclough covered a variety of mental disorders (e.g., major depression, schizophrenia) and did not exclusively focus on alcohol and drug-related disorders per se. Given our explicit focus on alcohol and drug use disorders, we expanded upon their approach in this domain by targeting alcohol and drug use disorders in the MEDLINE search strategy and by reading through four major alcohol and drug specialty journals. We also examined heterogeneity between studies in each alcohol and drug use disorder strata, as well as characteristics of studies (e.g., publication year, geographic region) that may account for heterogeneity in reports of alcohol and drug use disorders and risk for suicide. By expanding upon and updating their search, our goal has been to identify additional investigations of the association of suicide and drug use disorders, including studies that stratified by sex in order to examine the association of drug use disorders and suicide individually in women and men.

Section snippets

Search strategy

Our approach was to carry over Harris and Barraclough's fundamental approach to maintain consistency as well as to expand it in a targeted manner to provide better coverage of the alcohol and drug use disorders literature. Consistent with the review by Harris and Barraclough, the inclusion criterion were: (1) 2-plus years follow-up, (2) <10% lost to follow-up, (3) the observed number of suicides are specified, and (4) the authors provide the expected value for suicides or provide the necessary

Results

The obtained SMRs and 95% confidence intervals are presented for alcohol use disorders, opioid use disorders, mixed intravenous drug use, mixed (general) drug use, and heavy drinking. Intravenous drug use is a novel category, whereas the other alcohol and drug categories were previously presented by Harris and Barraclough.

Findings on alcohol use disorders and suicide are provided in Table 1. Harris and Barraclough reported combined sex data from 22 studies and we identified 11 additional

Discussion

Twenty studies not previously identified by Harris and Barraclough and 22 studies published since their review were combined with their data. The additional studies contributed to a more robust estimate of the association of suicide with opioid use disorders overall, alcohol use disorders among women, as well as novel summary data on the association of IV drug use and suicide. Alcohol and drug use disorders were associated with suicide for all categories of disorders for which data were

Acknowledgments

We would like to acknowledge the landmark empirical review by Harris and Barraclough (1997) that provided the foundation for this study and the assistance of Liz Schifano in gathering the data. This work was supported by NIH grants T32 MH019833, F31 DA14454, R03 AA13300, K23 AA00318, and R13 MH62073.

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