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The association between cannabis use and depression: a systematic review and meta-analysis of longitudinal studies

Published online by Cambridge University Press:  24 June 2013

S. Lev-Ran*
Affiliation:
Social Aetiology of Mental Illness (SAMI) CIHR Training Program, Centre for Addiction and Mental Health, Toronto, Ontario, Canada Social and Epidemiological Research Department, Centre for Addiction and Mental Health, Toronto, Ontario, Canada Addictions Program, Centre for Addiction and Mental Health, Toronto, Ontario, Canada Addiction Medicine Services, Department of Psychiatry, Sheba Medical Center, Tel Hashomer, Israel
M. Roerecke
Affiliation:
Social and Epidemiological Research Department, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
B. Le Foll
Affiliation:
Addictions Program, Centre for Addiction and Mental Health, Toronto, Ontario, Canada Translational Addiction Research Laboratory, Centre for Addiction and Mental Health, Toronto, Ontario, Canada Departments of Family and Community Medicine, Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada
T. P. George
Affiliation:
Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada Schizophrenia Program, Centre for Addiction and Mental Health, Toronto, Ontario, Canada Division of Brain and Therapeutics, Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada
K. McKenzie
Affiliation:
Social Aetiology of Mental Illness (SAMI) CIHR Training Program, Centre for Addiction and Mental Health, Toronto, Ontario, Canada Social and Epidemiological Research Department, Centre for Addiction and Mental Health, Toronto, Ontario, Canada Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada Social Equity and Health Research Program, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
J. Rehm
Affiliation:
Social and Epidemiological Research Department, Centre for Addiction and Mental Health, Toronto, Ontario, Canada Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
*
* Address for correspondence: S. Lev-Ran, Addiction Medicine Services, Department of Psychiatry, Sheba Medical Center, Tel Hashomer, Israel. (Email: shauli.levran@gmail.com)

Abstract

Background

Longitudinal studies reporting the association between cannabis use and developing depression provide mixed results. The objective of this study was to establish the extent to which different patterns of use of cannabis are associated with the development of depression using meta-analysis of longitudinal studies.

Method

Peer-reviewed publications reporting the risk of developing depression in cannabis users were located using searches of EMBASE, Medline, PsychINFO and ISI Web of Science. Only longitudinal studies that controlled for depression at baseline were included. Data on several study characteristics, including measures of cannabis use, measures of depression and control variables, were extracted. Odds ratios (ORs) were extracted by age and length of follow-up.

Results

After screening for 4764 articles, 57 articles were selected for full-text review, of which 14 were included in the quantitative analysis (total number of subjects = 76058). The OR for cannabis users developing depression compared with controls was 1.17 [95% confidence interval (CI) 1.05–1.30]. The OR for heavy cannabis users developing depression was 1.62 (95% CI 1.21–2.16), compared with non-users or light users. Meta-regression revealed no significant differences in effect based on age of subjects and marginal difference in effect based on length of follow-up in the individual studies. There was large heterogeneity in the number and type of control variables in the different studies.

Conclusions

Cannabis use, and particularly heavy cannabis use, may be associated with an increased risk for developing depressive disorders. There is need for further longitudinal exploration of the association between cannabis use and developing depression, particularly taking into account cumulative exposure to cannabis and potentially significant confounding factors.

Information

Type
Original Articles
Copyright
Copyright © Cambridge University Press 2013 

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