Cannabis use and subsequent onset of manic symptoms and bipolar disorder: A systematic review and meta-analysis.
Cecilia Sanjuan-Ortiz, Paula Querol, Claudia Aymerich et al.
✦ AI-curated · Sources linked
In 30 seconds
This registered systematic review and meta-analysis examined longitudinal observational studies of people without prior bipolar disorder, comparing those exposed and unexposed to cannabis. Across 19 studies involving 6,960,517 participants, cannabis use was associated with higher risks of subsequent bipolar disorder (RR = 2.46, 95% CI = 1.57-3.84; k = 8; N = 206.572) and manic/hypomanic symptoms (RR = 2.11, 95% CI = 1.07-4.18; k = 6; N = 57,243). The authors reported significant clinical and methodological sources of heterogeneity. These observational findings indicate association, not proof that cannabis causes bipolar-spectrum outcomes.
Key findings
- Cannabis exposure was associated with incident bipolar disorder: RR = 2.46, 95% CI = 1.57-3.84; k = 8; N = 206.572.
- Cannabis exposure was associated with subsequent manic/hypomanic symptoms: RR = 2.11, 95% CI = 1.07-4.18; k = 6; N = 57,243.
- Moderator analyses identified significant clinical and methodological sources of heterogeneity.
Why it matters
The findings add outcome-specific evidence that cannabis exposure is associated with later bipolar disorder and manic or hypomanic symptoms. This is relevant to prevention research because exposure may precede these outcomes, although the observational evidence cannot establish causation. The reported heterogeneity also cautions against assuming that the association is uniform across populations or study methods.
What to keep in mind
The included evidence was observational, and the pooled risk ratios were unadjusted. Significant clinical and methodological heterogeneity limits interpretation of a single overall estimate.