Cannabis, COMT and psychotic experiences

Stanley Zammit*, Michael J. Owen, Jonathan Evans, Jon Heron, Glyn Lewis

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

90 Citations (Scopus)

Abstract

Background: A putative interaction between cannabis and variation at rs4680 within the catechol-methyl-transferase (COMT) gene on psychosis has been reported, but not adequately replicated. Aims: To examine whether the relative risk of developing psychosis following use of cannabis is dependent upon variation within COMT. Method: A longitudinal study of 2630 individuals from the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort who completed questionnaire-based assessments for cannabis use at age 14 and incident psychotic experiences at age 16. Six SNPs within COMT were genotyped. Results: There was no evidence of an interaction under multiplicative models between cannabis use and COMT on the risk of developing psychotic experiences in our primary analyses. In sensitivity analyses we observed highly variable evidence of interaction, whereby psychotomimetic effects of cannabis were greater in methionine homozygotes under some scenarios, but in valine homozygotes under others. Conclusions: Cannabis increases risk of psychosis irrespective of underlying COMT genotypes. These findings argue against the widely held belief that the relative risk of developing psychosis following use of cannabis is dependent upon variation within COMT. The public health message about the potential increase in risk of psychotic disorders following cannabis use should not be tempered by reports that this harm is subgroup specific in the absence of robust evidence of replication. Declaration of interest: S.Z. and M.J.O. have received contributions from pharmaceutical companies as honoraria for talks.

Original languageEnglish
Pages (from-to)380-385
Number of pages6
JournalBritish Journal of Psychiatry
Volume199
Issue number5
DOIs
Publication statusPublished - Nov 2011

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