Meta-analysis of the Association Between the Level of Cannabis Use and Risk of Psychosis - PMC
Skip to main content
Official websites use .gov
.gov website belongs to an official<br>government organization in the United States.
Secure .gov websites use HTTPS
A lock (
Lock
Locked padlock icon
) or https:// means you've safely<br>connected to the .gov website. Share sensitive<br>information only on official, secure websites.
Search PMC Full-Text Archive
Search in PMC
Journal List
User Guide
PERMALINK
Copy
As a library, NLM provides access to scientific literature. Inclusion in an NLM database does not imply endorsement of, or agreement with,<br>the contents by NLM or the National Institutes of Health.
Learn more:<br>PMC Disclaimer
PMC Copyright Notice
Schizophr Bull<br>. 2016 Feb 15;42(5):1262–1269. doi: 10.1093/schbul/sbw003
Meta-analysis of the Association Between the Level of Cannabis Use and Risk of Psychosis
Arianna Marconi<br>Arianna Marconi
1Department of Psychosis Studies, King’s College London, Institute of Psychiatry Psychology & Neuroscience, London, UK;
Find articles by Arianna Marconi
1, Marta Di Forti<br>Marta Di Forti
1Department of Psychosis Studies, King’s College London, Institute of Psychiatry Psychology & Neuroscience, London, UK;
Find articles by Marta Di Forti
1, Cathryn M Lewis<br>Cathryn M Lewis
2King’s College London, Institute of Psychiatry Psychology & Neuroscience, MRC SGDP Centre, London, UK
Find articles by Cathryn M Lewis
2, Robin M Murray<br>Robin M Murray
1Department of Psychosis Studies, King’s College London, Institute of Psychiatry Psychology & Neuroscience, London, UK;
Find articles by Robin M Murray
1, Evangelos Vassos<br>Evangelos Vassos
2King’s College London, Institute of Psychiatry Psychology & Neuroscience, MRC SGDP Centre, London, UK
Find articles by Evangelos Vassos
2,*
Author information
Article notes
Copyright and License information
1Department of Psychosis Studies, King’s College London, Institute of Psychiatry Psychology & Neuroscience, London, UK;
2King’s College London, Institute of Psychiatry Psychology & Neuroscience, MRC SGDP Centre, London, UK
✉*To whom correspondence should be addressed; King’s College London, Institute of Psychiatry Psychology & Neuroscience, MRC SGDP Centre, Box P082, De Crespigny Park, London SE5 8AF, UK; tel: +44-20-7848-5433, fax: +44-20-7848-0866, e-mail: evangelos.vassos@kcl.ac.uk
Issue date 2016 Sep.
© The Author 2016. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email: journals.permissions@oup.com
PMC Copyright notice
PMCID: PMC4988731 PMID: 26884547
Abstract
Cannabis use has been reported to induce long-lasting psychotic disorders and a dose-response relationship has been observed. We performed a systematic review of studies that investigate the association between the degree of cannabis consumption and psychosis and a meta-analysis to quantify the magnitude of effect. Published studies were identified through search of electronic databases, supplemented by manual searches of bibliographies. Studies were considered if they provided data on cannabis consumption prior to the onset of psychosis using a dose criterion (frequency/amount used) and reported psychosis-related outcomes. We performed random effects meta-analysis of individual data points generated with a simulation method from the summary data of the original studies. From 571 references, 18 studies fulfilled inclusion criteria for the systematic review and 10 were inserted in the meta-analysis, enrolling a total of 66 816 individuals. Higher levels of cannabis use were associated with increased risk for psychosis in all the included studies. A logistic regression model gave an OR of 3.90 (95% CI 2.84 to 5.34) for the risk of schizophrenia and other psychosis-related outcomes among the heaviest cannabis users compared to the nonusers. Current evidence shows that high levels of cannabis use increase the risk of psychotic outcomes and confirms a dose-response relationship between the level of use and the risk for psychosis. Although a causal link cannot be unequivocally established, there is sufficient evidence to justify harm reduction prevention programs.
Key words: psychotic disorders, schizophrenia, dose response, drug use, systematic review
Introduction
The United Nations Office on Drugs and Crime (UNODC) reports that 3.9% of the global adult population uses cannabis, with a total number of 180.6 million of cannabis users worldwide.1 This outweighs the number of users of all other illicit substances considered together. In some countries, cannabis is categorized as a drug of abuse and its use is strictly prohibited, while in others it is perceived as a benign, relatively harmless substance.2–6 However, cannabis use has been widely reported to induce acute psychotic experiences,7–9 to affect the severity of psychotic symptoms,10,11 and previous meta-analyses...