Substance use disorder and risk of suicidal ideation, suicide attempt and suicide death: a meta-analysis.

Background: This meta-analysis addressed the association between substance use disorder (SUD) and suicide outcomes based on current evidence.
Methods: We searched PubMed, Web of Science and Scopus until May 2015. We also searched the reference lists of included studies and Psycinfo website. We included observational (cohort, case-control, cross-sectional) studies addressing the association between SUD and suicide. Our outcomes of interest were suicide ideation, suicide attempt and suicide death. For each outcome, we calculated the odds ratio (OR) or risk ratio (RR) with 95% confidence intervals (CI) based on the random-effects model.
Results: We identified a total of 12 413 references and included 43 studies with 870 967 participants. There was a significant association between SUD and suicidal ideation: OR 2.04 (95% CI: 1.59, 2.50; I ² = 88.8%, 16 studies); suicide attempt OR 2.49 (95% CI: 2.00, 2.98; I ² = 94.3%, 24 studies) and suicide death OR 1.49 (95% CI: 0.97, 2.00; I ² = 82.7%, 7 studies).
Conclusions: Based on current evidence, there is a strong association between SUD and suicide outcomes. However, evidence based on long-term prospective cohort studies is limited and needs further investigation. Moreover, further evidence is required to assess and compare the association between suicide outcomes and different types of illicit drugs, dose-response relationship and the way they are used.
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