Cannabis Use Linked to Increased Risk of Bipolar Disorder and Mania: Study
A meta-analysis of longitudinal studies found that cannabis use was associated with more than twice the risk of developing bipolar disorder and nearly twice the risk of subsequent manic or hypomanic symptoms compared with non-use. These associations were observed in individuals without bipolar disorder or relevant mood symptoms at baseline, highlighting the potential importance of cannabis avoidance in reducing the risk of future mood disturbances. The study was published in the Journal of Affective Disorders by Cecilia S. and colleagues.
To estimate the potential association between cannabis, use and later development of bipolar spectrum disorders, researchers carried out a pre-registered systematic review and meta-analysis on PubMed and Web of Science from their beginning up until October 2025. The methodological protocol entailed longitudinal studies that involved the comparison of cannabis users and non-users who did not have baseline bipolar disorder at all.
Meta-analysis was performed using random effect models that provided unadjusted risk ratio estimates (RR) of two different outcome measures, namely incidence of bipolar disorder and mania or hypomania. The methodological quality of the included studies was assessed with the use of the Newcastle–Ottawa Scale (NOS).
Key findings:
- The systematic review synthesized data across 19 longitudinal studies encompassing a total cohort of 6,960,517 participants (mean age 23.8 ± 11.8 years; 49% female), yielding high methodological consistency.
- Across 8 studies involving 206,572 participants, cannabis use was associated with a statistically significant twofold increase in the risk of incident bipolar disorder (RR = 2.46, 95% CI = 1.57–3.84; k = 8).
- Across 6 studies encompassing 57,243 participants, cannabis exposure was associated with a twofold higher risk of developing manic or hypomanic symptoms (RR = 2.11, 95% CI = 1.07–4.18; k = 6).
- Included studies demonstrated good to high methodological quality, with Newcastle–Ottawa Scale scores ranging from 6 to 9.
- Risk estimates remained robust across various cannabis exposure definitions and age cohorts, with moderator analyses identifying key clinical sources of heterogeneity.
In summary, based on meta-analytic evidence involving more than 6.9 million people, there is strong support for the fact that cannabis use raises the prospective risk of bipolar disorder and manic features. The findings of the study highlight that cannabis is an important modifiable risk factor, and thus should be considered in prevention programs.
Reference:
Sanjuan-Ortiz, C., Querol, P., Aymerich, C., Laherran, N., Ditlevsen, F., Navalón, P., Rojo-Bofill, L. M., Young, A. H., Celso, A., Sharma, A., Di Forti, M., Murray, R. M., Correll, C. U., & de Pablo, G. S. (2027). Cannabis use and subsequent onset of manic symptoms and bipolar disorder: A systematic review and meta-analysis. Journal of Affective Disorders, 416, 122588. https://doi.org/10.1016/j.jad.2026.122588
