More evidence that using cannabis may cause earlier onset of psychosis

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This meta-analysis adds more weight to the argument that cannabis use plays a causal role in the development of psychosis in some patients.

The review pooled 83 studies that reported on age at onset of psychotic illness in substance-using and non–substance-using groups.

The study found that:

  • Age at onset of psychosis for cannabis users was 2.70 years younger (standardized mean difference = –0.414) than for nonusers
  • For those with broadly defined substance use, the age at onset of psychosis was 2.00 years younger (standardized mean difference = –0.315) than for nonusers
  • Alcohol use was not associated with a significantly earlier age at onset of psychosis

Large, M. Sharma, S. Compton, MT. Slade, T. Nielssen, O. Cannabis Use and Earlier Onset of Psychosis: A Systematic Meta-analysis. Arch Gen Psychiatry. 2011;68(6):555-561. doi:10.1001/archgenpsychiatry.2011.5 [Abstract]

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Andre Tomlin

Andre Tomlin

André Tomlin is an Information Scientist with 20 years experience working in evidence-based healthcare. He's worked in the NHS, for Oxford University and since 2002 as Managing Director of Minervation Ltd, a consultancy company who do clever digital stuff for charities, universities and the public sector. Most recently André has been the driving force behind the Mental Elf and the National Elf Service; an innovative digital platform that helps professionals keep up to date with simple, clear and engaging summaries of evidence-based research. André is a Trustee at the Centre for Mental Health and an Honorary Research Fellow at University College London Division of Psychiatry. He lives in Bristol with his wife, dog and three little elflings.

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