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Brain Morphology of Cannabis Users With or Without Psychosis: A Pilot MRI Study

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Published on: August 18, 2020

Cannabis, COMT and psychotic experiences.

Stanley Zammit¹, Michael J Owen, Jonathan Evans

¹Department of Psychological Medicine & Neurology, MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Heath Park, Cardiff CF14 4XN, UK. zammits@cardiff.ac.uk

The British Journal of Psychiatry : the Journal of Mental Science

|September 28, 2011

Summary

Cannabis use increases psychosis risk regardless of COMT gene variations. This study found no evidence that genetic differences in the catechol-O-methyltransferase (COMT) gene alter the risk of psychosis from cannabis use.

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Area of Science:

Neuroscience
Genetics
Psychiatry

Background:

Previous research suggested a link between cannabis use, COMT gene variations (rs4680), and psychosis risk.
This interaction hypothesis lacked sufficient replication.

Purpose of the Study:

To investigate if cannabis use elevates psychosis risk differently based on variations in the catechol-O-methyltransferase (COMT) gene.
To test the hypothesis that COMT genotype modifies the association between cannabis use and psychotic experiences.

Main Methods:

A longitudinal study of 2630 participants from the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort.
Assessed cannabis use at age 14 and psychotic experiences at age 16.
Genotyped six single nucleotide polymorphisms (SNPs) within the COMT gene.

Main Results:

Primary analyses showed no evidence of interaction between cannabis use and COMT genotype on psychosis risk under multiplicative models.
Sensitivity analyses yielded inconsistent results, with some scenarios suggesting greater cannabis effects in methionine homozygotes and others in valine homozygotes.

Conclusions:

Cannabis use elevates psychosis risk independently of COMT gene variations.
Findings challenge the notion that COMT genotype influences the cannabis-psychosis risk relationship.
Public health messaging on cannabis risks should not be qualified by unproven subgroup-specific harm.