A meta-analysis of prospective studies found cannabis use associated with approximately 3 times the risk of developing new manic symptoms, and with worsening mania in those already diagnosed with bipolar disorder.
Read this if you have bipolar disorder or a family history and use cannabis.
OR 2.97: ~3x risk of new-onset manic symptoms with cannabis use
What the researchers found
Researchers conducted a systematic review following PRISMA guidelines, searching five databases for prospective studies on cannabis use and mania. Six articles met inclusion criteria, covering 2,391 individuals who had experienced manic symptoms with a mean follow-up of 3.9 years.
Studies supported an association between cannabis use and worsened manic symptoms in people with existing bipolar disorder diagnoses. A meta-analysis of two studies found cannabis use was associated with approximately 3 times the risk (OR 2.97, 95% CI: 1.80-4.90) of developing new-onset manic symptoms.
The authors noted their conclusions were preliminary due to the small number of studies and variable quality, but the direction and magnitude of the association was consistent across analyses.
Why it matters
While cannabis-psychosis links are well-studied, the cannabis-mania relationship receives less attention. A nearly 3-fold risk increase for new manic symptoms is clinically significant and relevant for both prevention messaging and management of people with or at risk for bipolar disorder.
The numbers in context
6 studies, 2,391 individuals with mania. Mean follow-up: 3.9 years. Meta-analysis OR: 2.97 (95% CI: 1.80-4.90) for new-onset manic symptoms. Cannabis worsened mania in those with existing bipolar disorder.
How the study worked
Systematic review following PRISMA guidelines, searching PsychINFO, Cochrane, Scopus, Embase, and MEDLINE for prospective studies. Six studies met criteria (2,391 individuals, mean follow-up 3.9 years). Meta-analysis of two studies estimated the odds ratio for new-onset manic symptoms.
What this study cannot tell us
Only 6 studies met criteria, and only 2 were included in the meta-analysis. Variable study quality. The small evidence base makes conclusions preliminary. Confounders may not be fully addressed across all studies.
How to read the evidence
Systematic review and meta-analysis of prospective studies, but limited by small number of qualifying studies.
When this study was published
Published in 2015. Cannabis-mania research has continued with additional prospective studies.
The bigger picture
The cannabis-psychosis discussion has largely focused on schizophrenia-like symptoms. This review broadens that conversation to include bipolar mania, another major psychiatric condition. If cannabis is both a risk factor for mania onset and a worsening factor for existing bipolar disorder, this is important clinical information.
Questions still open
- Does the risk of mania differ by cannabis potency or frequency of use? Could cannabis trigger manic episodes in people with undiagnosed bipolar vulnerability? Would CBD-dominant cannabis products carry the same risk?
Common questions
Can cannabis trigger mania?
Should people with bipolar disorder avoid cannabis?
Read the original research
Cannabis use and mania symptoms: a systematic review and meta-analysis.
Journal of affective disorders, 171, 39-47
Citation
Gibbs, Melanie; Winsper, Catherine; Marwaha, Steven; Gilbert, Eleanor; Broome, Matthew; Singh, Swaran P. (2015). Cannabis use and mania symptoms: a systematic review and meta-analysis.. Journal of affective disorders, 171, 39-47. https://doi.org/10.1016/j.jad.2014.09.016
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