In 109,308 UK Biobank participants, cannabis use showed a strong dose-dependent association with psychotic experiences, and people with high schizophrenia polygenic risk were disproportionately affected.
Psychiatrists, genetic counselors, psychosis researchers, and public health officials.
67% increased odds of delusions in high genetic risk group vs. 7% in low risk
What the researchers found
Cannabis ever-use was associated with 67% greater adjusted odds of delusions of reference among individuals in the top fifth of schizophrenia polygenic risk, but only 7% greater adjusted odds among the bottom fifth. The cannabis-psychosis association was strongest for persecutory delusions and showed clear dose-dependence.
Why it matters
This is among the largest studies to show gene-environment interaction between schizophrenia genetic risk and cannabis use, supporting the hypothesis that genetically vulnerable individuals face greater psychosis risk from cannabis.
The numbers in context
Sample: 109,308 participants. Top PRS fifth: 67% increased odds of delusions of reference with cannabis use. Bottom PRS fifth: 7% increased odds. Strongest association: persecutory delusions. Cannabis users had earlier onset and more distressing psychotic experiences.
How the study worked
Cross-sectional study of 109,308 UK Biobank participants examining self-reported cannabis use against four types of psychotic experiences (auditory hallucinations, visual hallucinations, persecutory delusions, delusions of reference), stratified by schizophrenia polygenic risk scores.
What this study cannot tell us
Cross-sectional design cannot establish temporal sequence. Self-reported cannabis use and psychotic experiences. UK Biobank participants may not be representative of the general population. Polygenic risk scores explain only a fraction of schizophrenia heritability.
How to read the evidence
Very large biobank sample with validated polygenic risk scores, though cross-sectional design limits causal inference.
When this study was published
Published in 2021.
The bigger picture
These findings point toward a future where polygenic risk scores could inform personalized harm reduction, identifying individuals for whom cannabis use carries disproportionate psychosis risk.
Questions still open
- Could polygenic risk scores eventually be used clinically to counsel individuals about cannabis risk? Does the type of cannabis product (high-THC vs. balanced) modify this gene-environment interaction?
Common questions
Does genetic risk change how cannabis affects psychosis risk?
What type of psychotic experience was most strongly linked to cannabis?
Read the original research
Cannabis, schizophrenia genetic risk, and psychotic experiences: a cross-sectional study of 109,308 participants from the UK Biobank.
Translational psychiatry, 11(1), 211
Citation
Wainberg, Michael; Jacobs, Grace R; di Forti, Marta; Tripathy, Shreejoy J. (2021). Cannabis, schizophrenia genetic risk, and psychotic experiences: a cross-sectional study of 109,308 participants from the UK Biobank.. Translational psychiatry, 11(1), 211. https://doi.org/10.1038/s41398-021-01330-w
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