A meta-analysis of 29 studies found cannabis use in schizophrenia was associated with 40% higher odds of suicide attempts and 21% higher risk of suicide death.
Psychiatrists treating schizophrenia, suicide prevention researchers, clinical risk assessors
40% higher suicide attempt odds with cannabis use in schizophrenia
What the researchers found
Across 29 studies (36 samples), cannabis use was associated with 40% higher odds of attempted suicide (OR=1.40, 95% CI: 1.16-1.68) and 21% higher risk of suicide death (HR=1.21, 95% CI: 1.04-1.40). Cannabis was not significantly associated with suicidal ideation alone.
Why it matters
Suicide is a leading cause of death in schizophrenia. Identifying cannabis use as a risk factor for suicide attempts and death provides an actionable target for clinical intervention.
The numbers in context
29 studies, 36 samples. Attempted suicide OR=1.40 (95% CI: 1.16-1.68). Suicide death HR=1.21 (95% CI: 1.04-1.40). Suicidal ideation: not significant. Heterogeneity moderate for attempts (I2=39.6%).
How the study worked
Systematic review and meta-analysis of cross-sectional, case-control, and longitudinal studies from Medline, Embase, and PsycINFO through November 2024, using random effects models.
What this study cannot tell us
Cannot establish causality from meta-analysis of observational studies. Cannabis use may be a marker for severity rather than a direct cause. Some subgroup analyses lost significance. Confounding by other substance use possible.
How to read the evidence
Large meta-analysis with comprehensive search and appropriate statistical methods, though underlying studies are observational.
When this study was published
2025 meta-analysis with search through November 2024.
The bigger picture
Cannabis is the most commonly used substance in schizophrenia. If it increases suicide risk by 20-40%, this has major implications for clinical management, especially given the already elevated baseline suicide risk in this population.
Questions still open
- Does reducing cannabis use lower suicide risk in schizophrenia? What mechanisms link cannabis to increased suicide risk? Should cannabis screening be part of suicide risk assessment in psychosis?
Common questions
Does cannabis increase suicide risk in people with schizophrenia?
Should cannabis use be screened as part of suicide risk in psychosis?
Read the original research
Cannabis use and suicide in people with a diagnosis of schizophrenia: a systematic review and meta-analysis of longitudinal, case control, and cross-sectional studies.
Psychological medicine, 55, e79
Citation
Mulligan, Lee D; Varese, Filippo; Harris, Kamelia; Haddock, Gillian. (2025). Cannabis use and suicide in people with a diagnosis of schizophrenia: a systematic review and meta-analysis of longitudinal, case control, and cross-sectional studies.. Psychological medicine, 55, e79. https://doi.org/10.1017/S0033291725000236
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