Psychiatric effects of cannabis

Br J Psychiatry. 2001 Feb:178:116-22. doi: 10.1192/bjp.178.2.116.


Background: Cannabis is commonly regarded as an innocuous drug and the prevalence of lifetime and regular use has increased in most developed countries. However, accumulative evidence highlights the risks of dependence and other adverse effects, particularly among people with pre-existing psychiatric disorders.

Aims: To re-evaluate the adverse effects of cannabis in the general population and among vulnerable individuals, including those with serious psychiatric disorders.

Method: A wide-ranging review of the topics related to these issues. Results and conclusions An appreciable proportion of cannabis users report short-lived adverse effects, including psychotic states following heavy consumption, and regular users are at risk of dependence. People with major mental illnesses such as schizophrenia are especially vulnerable in that cannabis generally provokes relapse and aggravates existing symptoms. Health workers need to recognise, and respond to, the adverse effects of cannabis on mental health.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Affective Symptoms / chemically induced*
  • Cannabis / adverse effects*
  • Cognition Disorders / chemically induced
  • Female
  • Humans
  • Male
  • Marijuana Abuse / epidemiology
  • Marijuana Abuse / psychology*
  • Psychoses, Substance-Induced / etiology*
  • Psychotic Disorders / epidemiology
  • Psychotropic Drugs / adverse effects*
  • Risk Factors
  • Substance Withdrawal Syndrome / etiology


  • Psychotropic Drugs