A meta-analysis found that any cannabis use was associated with a 2.6x increased risk of suicide death, 1.4x risk of suicidal ideation, and 2.2x risk of suicide attempt, with heavy use roughly doubling these associations.
Clinicians assessing suicide risk and anyone interested in the relationship between cannabis and mental health.
Heavy cannabis use associated with 3.2x increased risk of suicide attempt
What the researchers found
This review and meta-analysis examined the relationship between cannabis use and suicidality across three outcomes: suicide death, suicidal ideation, and suicide attempt.
For chronic cannabis use, the pooled odds ratios from meta-analyses were: suicide death (2.56, based on 4 studies), suicidal ideation with any use (1.43, from 6 studies) and heavy use (2.53, from 5 studies), and suicide attempt with any use (2.23, from 6 studies) and heavy use (3.20, from 6 studies).
For acute cannabis use, the evidence was mostly limited to toxicology reports finding cannabis in approximately 9.5% of suicide decedents, with higher detection rates among those who died by non-overdose methods. The authors concluded that chronic cannabis use can predict suicidality, but noted inconsistent measurement of cannabis exposure and sometimes inadequate control for known risk factors.
Why it matters
These findings quantify the association between cannabis use and suicide risk across multiple outcomes. The dose-response pattern (heavier use associated with greater risk) adds plausibility to the association, though the authors cautioned about confounding.
The numbers in context
Suicide death: OR 2.56 (4 studies). Suicidal ideation (any use): OR 1.43 (6 studies). Suicidal ideation (heavy use): OR 2.53 (5 studies). Suicide attempt (any use): OR 2.23 (6 studies). Suicide attempt (heavy use): OR 3.20 (6 studies). Acute cannabis detection in suicides: 9.5%.
How the study worked
Systematic search of Medline, PsychInfo, Google Scholar, and public databases for the period 1990-2015. Random effects meta-analyses were conducted separately for any cannabis use versus heavy cannabis use and for each suicidality outcome.
What this study cannot tell us
The authors acknowledged lack of homogeneity in how cannabis exposure was measured across studies, and in some cases insufficient control for known suicide risk factors (depression, other substance use, childhood adversity). The number of studies for some outcomes was small (4 for suicide death). Observational data cannot prove cannabis causes suicidality.
How to read the evidence
This is a systematic review with meta-analysis pooling data across multiple studies, providing strong evidence for the association, though the quality of included studies varied.
When this study was published
Published in 2016, covering literature from 1990-2015. Additional studies on this topic have been published since then.
The bigger picture
The cannabis-suicide association is one of the more concerning findings in cannabis epidemiology. While this meta-analysis cannot prove causation, the consistency across outcomes and the dose-response relationship are notable and have implications for clinical screening and risk assessment.
Questions still open
- Does cannabis use directly increase suicide risk, or is it a marker for other risk factors? Would adequate control for all known confounders eliminate the association?
Common questions
Does cannabis use cause suicidal thoughts?
Should people with suicidal thoughts avoid cannabis?
Read the original research
A literature review and meta-analyses of cannabis use and suicidality.
Journal of affective disorders, 195, 63-74
Citation
Borges, Guilherme; Bagge, Courtney L; Orozco, Ricardo. (2016). A literature review and meta-analyses of cannabis use and suicidality.. Journal of affective disorders, 195, 63-74. https://doi.org/10.1016/j.jad.2016.02.007
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