Cannabis Use Made Bipolar Disorder Treatment Outcomes Worse Over 12 Months
Among 3,459 bipolar disorder patients followed for 12 months, cannabis users showed less treatment compliance and higher levels of illness severity, mania, and psychosis compared to non-users.
Quick Facts
What This Study Found
In an observational study of 3,459 bipolar disorder patients (both inpatient and outpatient), researchers tracked the influence of cannabis use on treatment outcomes over one year.
Cannabis users exhibited less medication compliance and higher levels of overall illness severity, mania, and psychosis compared to non-users throughout the 12-month treatment period.
Cannabis users also experienced less life satisfaction and had a lower probability of being in a relationship.
There was little evidence that these associations were explained by third variables (mediators), suggesting an independent impact of cannabis on clinical outcomes in bipolar disorder.
The impact on psychopathological outcomes was pronounced, while the impact on social outcomes was more modest.
Key Numbers
3,459 bipolar patients followed for 12 months. Cannabis users had higher overall illness severity, mania, psychosis, lower treatment compliance, less life satisfaction, and lower relationship probability.
How They Did This
Observational longitudinal study (EMBLEM) enrolling 3,459 bipolar in- and outpatients. Cannabis exposure was assessed and clinical/social outcomes were tracked over 12 months. Mediation analysis tested whether third variables explained the cannabis-outcome associations.
Why This Research Matters
With a large sample and mediation analysis finding little evidence of confounding, this study provided relatively strong evidence that cannabis independently worsens bipolar disorder outcomes.
The Bigger Picture
While much research has focused on cannabis and schizophrenia, this study showed that cannabis also affects outcomes in bipolar disorder, broadening the evidence that cannabis use complicates the treatment of serious mental illness.
What This Study Doesn't Tell Us
Observational design cannot definitively establish causation. Cannabis users may have more severe illness at baseline. Self-reported cannabis use may be unreliable. The study did not quantify cannabis use amounts.
Questions This Raises
- ?Does cannabis use cause worse bipolar outcomes or do more severe patients use cannabis?
- ?Would cannabis cessation improve bipolar treatment response?
- ?Are certain bipolar subtypes more affected by cannabis use?
Trust & Context
- Key Stat:
- 3,459 bipolar patients: cannabis users had more mania, psychosis, and less treatment compliance
- Evidence Grade:
- Large longitudinal observational study with mediation analysis. Strong sample size but observational design limits causal inference.
- Study Age:
- Published in 2009. Subsequent research has generally supported the finding that cannabis use complicates mood disorder treatment.
- Original Title:
- Does cannabis use affect treatment outcome in bipolar disorder? A longitudinal analysis.
- Published In:
- The Journal of nervous and mental disease, 197(1), 35-40 (2009)
- Database ID:
- RTHC-00394
Evidence Hierarchy
Follows a group of people over time to track how outcomes develop.
What do these levels mean? →Frequently Asked Questions
Does cannabis make bipolar disorder worse?
This large study found that cannabis-using bipolar patients had worse outcomes across multiple measures. While observational data cannot prove causation, the mediation analysis found little evidence that other factors explained the association.
Could cannabis help with some bipolar symptoms?
Some bipolar patients report using cannabis for symptom management. However, this study found that cannabis users had worse overall outcomes including more mania and psychosis, suggesting that any perceived benefits may not outweigh the harms at a population level.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-00394APA
van Rossum, Inge; Boomsma, Maarten; Tenback, Diederik; Reed, Catherine; van Os, Jim. (2009). Does cannabis use affect treatment outcome in bipolar disorder? A longitudinal analysis.. The Journal of nervous and mental disease, 197(1), 35-40. https://doi.org/10.1097/NMD.0b013e31819292a6
MLA
van Rossum, Inge, et al. "Does cannabis use affect treatment outcome in bipolar disorder? A longitudinal analysis.." The Journal of nervous and mental disease, 2009. https://doi.org/10.1097/NMD.0b013e31819292a6
RethinkTHC
RethinkTHC Research Database. "Does cannabis use affect treatment outcome in bipolar disord..." RTHC-00394. Retrieved from https://rethinkthc.com/research/van-2009-does-cannabis-use-affect
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.