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Cannabis use and mental health in young people: cohort study

BMJ 2002; 325 doi: https://doi.org/10.1136/bmj.325.7374.1195 (Published 23 November 2002) Cite this as: BMJ 2002;325:1195
  1. George C Patton, professor of adolescent health (gpatton{at}cryptic.rch.unimelb.edu.au)a,
  2. Carolyn Coffey, epidemiologista,
  3. John B Carlin, director of unitb,
  4. Louisa Degenhardt, research fellowc,
  5. Michael Lynskey, visiting research fellowd,
  6. Wayne Hall, professor of bioethicse
  1. a Centre for Adolescent Health, Murdoch Children's Research Institute, Parkville, Victoria 3052, Australia
  2. b Clinical Epidemiology and Biostatistics Unit, Murdoch Children's Research Institute
  3. c National Drug and Alcohol Research Centre, University of New South Wales, Sydney 2052, Australia
  4. d Department of Psychiatry, Washington University School of Medicine, St Louis, MO 63110, USA
  5. e Office of Public Policy and Ethics, Institute for Molecular Bioscience, University of Queensland, Brisbane 4072, Australia
  1. Correspondence to: G Patton
  • Accepted 15 August 2002

Abstract

Objective: To determine whether cannabis use in adolescence predisposes to higher rates of depression and anxiety in young adulthood.

Design: Seven wave cohort study over six years.

Setting: 44 schools in the Australian state of Victoria.

Participants: A statewide secondary school sample of 1601 students aged 14-15 followed for seven years.

Main outcome measure: Interview measure of depression and anxiety (revised clinical interview schedule) at wave 7.

Results: Some 60% of participants had used cannabis by the age of 20; 7% were daily users at that point. Daily use in young women was associated with an over fivefold increase in the odds of reporting a state of depression and anxiety after adjustment for intercurrent use of other substances (odds ratio 5.6, 95% confidence interval 2.6 to 12). Weekly or more frequent cannabis use in teenagers predicted an approximately twofold increase in risk for later depression and anxiety (1.9, 1.1 to 3.3) after adjustment for potential baseline confounders. In contrast, depression and anxiety in teenagers predicted neither later weekly nor daily cannabis use.

Conclusions: Frequent cannabis use in teenage girls predicts later depression and anxiety, with daily users carrying the highest risk. Given recent increasing levels of cannabis use, measures to reduce frequent and heavy recreational use seem warranted.

What is already known on this topic

What is already known on this topic Frequent recreational use of cannabis has been linked to high rates of depression and anxiety in cross sectional surveys and studies of long term users

Why cannabis users have higher rates of depression and anxiety is uncertain

Previous longitudinal studies of cannabis use in youth have not analysed associations with frequent cannabis use

What this study adds

What this study adds A strong association between daily use of cannabis and depression and anxiety in young women persists after adjustment for intercurrent use of other substances

Frequent cannabis use in teenage girls predicts later higher rates of depression and anxiety

Depression and anxiety in teenagers do not predict later cannabis use; self medication is therefore unlikely to be the reason for the association

Footnotes

  • Editorial by Rey and Tennant

  • Funding National Health and Medical Research Council and Victorian Health Promotion Foundation.

  • Competing interests None declared.

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