Cannabis use and earlier onset of psychosis

January 01, 0001

Cannabis use and earlier onset of psychosis

This meta-analysis by Australian and US authors was conducted to establish the extent to which use of cannabis, alcohol, and other psychoactive substances affects the age at onset of psychosis. They included studies in English comparing the age at onset of psychosis in cohorts of patients who use substances with age at onset of psychosis in non-substance-using patients. The searches yielded 443 articles, from which 83 studies met the inclusion criteria.

They found: "Meta-analysis found that the age at onset of psychosis for cannabis users was 2.70 years younger than for nonusers; for those with broadly defined substance use, the age at onset of psychosis was 2.00 years younger than for nonusers. Alcohol use was not associated with a significantly earlier age at onset of psychosis. Differences in the proportion of cannabis users in the substance-using group made a significant contribution to the heterogeneity in the effect sizes between studies, confirming an association between cannabis use and earlier mean age at onset of psychotic illness."

The authors concluded: "The results of meta-analysis provide evidence for a relationship between cannabis use and earlier onset of psychotic illness, and they support the hypothesis that cannabis use plays a causal role in the development of psychosis in some patients. The results suggest the need for renewed warnings about the potentially harmful effects of cannabis."

Both the medical community and the public should be aware of this risk.


For the full abstract, click here.

Arch Gen Psychiatry 68(6):555-561, June 2011 © 2011 to the American Medical Association
Cannabis Use and Earlier Onset of Psychosis-A Systematic Meta-analysis. Matthew Large, Swapnil Sharma, Michael T. Compton, Tim Slade, Olav Nielssen. Correspondence to Dr. Large: [email protected]

Category: Z. Social Problems, P. Psychological. Keywords: cannabis, psychosis, substance abuse, meta-analysis of cohort studies, journal watch.
Synopsis edited by Dr Linda French, Toledo, Ohio. Posted on Global Family Doctor 21 June 2011

Pearls are an independent product of the Cochrane primary care group and are meant for educational use and not to guide clinical care.

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