Cannabis use and subsequent onset of manic symptoms and bipolar disorder: A systematic review and meta-analysis.

What was studied

This review asked if cannabis use is linked to later bipolar disorder or manic symptoms. The team looked at these outcomes apart. It searched PubMed and Web of Science up to October 2025. It used studies that followed people over time. They compared people who did and did not use cannabis. None had bipolar disorder at the start. Study quality was rated with the Newcastle-Ottawa Scale. The total sample was 6,960,517.

What they found

Cannabis use was linked with higher risk of bipolar disorder. The risk ratio was 2.46. It was also linked with higher risk of manic or hypomanic symptoms. That risk ratio was 2.11. Further analyses found clinical and method reasons why results varied. Quality scores ranged from 6 to 9. This points to good to high quality.

What it means for patients

The authors say cannabis use was linked to higher risk of later bipolar-spectrum outcomes. They say routine checks of cannabis use may be warranted. They pair this with prevention to delay and cut use.

Why it is not certain yet

The risk ratios were not adjusted for other factors. The studies were observational. Observational data show links, not cause. Results varied between studies. Only studies with data that could be pulled out were pooled.

Source

Cannabis use and subsequent onset of manic symptoms and bipolar disorder: A systematic review and meta-analysis.

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