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Updated: Jun 13, 2026

Brain Morphology of Cannabis Users With or Without Psychosis: A Pilot MRI Study
Published on: August 18, 2020
[The influence of cannabis on the course of bipolar disorder: a longitudinal analysis]
I Winter-van Rossum1, M M Boomsma, D E Tenback
1Lilly Nederland B.V., Houten. winter_van_rossum_inge@lilly.com
Background:
Research shows that the use of cannabis has a negative impact on the onset and outcome of schizophrenia, but little is known about possible effects on mood disorders.
Aim:
To study the influence of cannabis use on clinical and social treatment outcomes in patients with bipolar disorders who had been treated for a period of 12 months.
Method:
3459 bipolar patients were enrolled in an observational study. The influence of cannabis on various clinical and social treatment outcomes was examined over a period of one year. In addition, tests were applied in order to find out whether third, mediating variables had effects on possible associations between cannabis use and treatment outcomes.
Results:
During 12 months of treatment cannabis users showed less compliance and higher levels of illness severity, mania and psychosis than did non-users. In addition, cannabis users were less satisfied with their lives and had less chance of forming relationships than non-users. There was little evidence that associations between cannabis use and treatment outcomes were mediated by third variables.
Conclusion:
Cannabis use clearly had an independent impact on clinical treatment outcomes in patients with bipolar disorder, but the impact on social outcomes was only modest.
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