Regular Cannabis Use Lowers Remission Rates in Bipolar Disorder
In a 24-month study, regular cannabis use was associated with significantly lower remission rates in patients with bipolar I and schizoaffective disorder, with the worst outcomes in those who also smoked tobacco.
Quick Facts
What This Study Found
Researchers followed 234 patients with bipolar I disorder or schizoaffective disorder for 24 months. About 11% were regular cannabis users (three or more times per week).
Cannabis use was significantly associated with lower likelihood of achieving remission. The pattern differed by sex: in women, cannabis was linked to lower depression remission, while in men, it was linked to lower mania remission.
The lowest remission rates were in patients who used both cannabis and tobacco, followed by tobacco-only users, with non-smokers having the best outcomes.
Key Numbers
234 participants analyzed; 25 (10.7%) regular cannabis users; 24-month follow-up; combined cannabis and tobacco group had the lowest remission rates; sex-specific effects on depression (women) versus mania (men)
How They Did This
Prospective observational study following 239 patients with bipolar I or schizoaffective disorder (bipolar type) over 24 months. Regular cannabis use defined as three or more times per week. Outcomes measured using the Hamilton Depression Rating Scale and Young Mania Rating Scale at evaluations throughout the follow-up period.
Why This Research Matters
This study provides longitudinal evidence that cannabis use complicates bipolar disorder treatment, and reveals that the impact may differ between men and women and interact with tobacco use.
The Bigger Picture
For people with bipolar spectrum disorders, cannabis use appears to work against the goals of treatment. The interaction with tobacco and sex-specific effects suggest that substance use management needs to be individualized within bipolar treatment plans.
What This Study Doesn't Tell Us
Observational design cannot prove cannabis caused worse outcomes. Regular cannabis users may differ from non-users in ways not fully captured. Small number of cannabis users (n=25) limits statistical power. Dose and potency were not measured.
Questions This Raises
- ?Why does cannabis appear to affect depression in women but mania in men with bipolar disorder?
- ?Would reducing cannabis use improve remission rates?
- ?Does the type or potency of cannabis matter?
Trust & Context
- Key Stat:
- Combined cannabis and tobacco users had the lowest remission rates
- Evidence Grade:
- Prospective 24-month follow-up with validated outcome measures, though limited by small cannabis user subgroup and observational design.
- Study Age:
- Published in 2015. Treatment approaches for bipolar disorder have continued to evolve.
- Original Title:
- Impact of Cannabis Use on Long-Term Remission in Bipolar I and Schizoaffective Disorder.
- Published In:
- Psychiatry investigation, 12(3), 349-55 (2015)
- Authors:
- Kim, Sung-Wan, Dodd, Seetal, Berk, Lesley, Kulkarni, Jayashri, de Castella, Anthony, Fitzgerald, Paul B, Kim, Jae-Min, Yoon, Jin-Sang, Berk, Michael
- Database ID:
- RTHC-00991
Evidence Hierarchy
Follows a group of people over time to track how outcomes develop.
What do these levels mean? →Frequently Asked Questions
Why did cannabis affect men and women differently?
In women, cannabis was linked to lower depression remission, while in men it was linked to lower mania remission. The biological mechanisms are unclear, but sex differences in cannabinoid receptor density and hormonal interactions may play a role.
Does this mean cannabis causes bipolar episodes?
The study found an association between cannabis use and lower remission rates but cannot prove causation. It is possible that people with more severe illness are also more likely to use cannabis.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-00991APA
Kim, Sung-Wan; Dodd, Seetal; Berk, Lesley; Kulkarni, Jayashri; de Castella, Anthony; Fitzgerald, Paul B; Kim, Jae-Min; Yoon, Jin-Sang; Berk, Michael. (2015). Impact of Cannabis Use on Long-Term Remission in Bipolar I and Schizoaffective Disorder.. Psychiatry investigation, 12(3), 349-55. https://doi.org/10.4306/pi.2015.12.3.349
MLA
Kim, Sung-Wan, et al. "Impact of Cannabis Use on Long-Term Remission in Bipolar I and Schizoaffective Disorder.." Psychiatry investigation, 2015. https://doi.org/10.4306/pi.2015.12.3.349
RethinkTHC
RethinkTHC Research Database. "Impact of Cannabis Use on Long-Term Remission in Bipolar I a..." RTHC-00991. Retrieved from https://rethinkthc.com/research/kim-2015-impact-of-cannabis-use
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.