title: Psychiatric effects of cannabis.
abstract: 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.
  
  
  OBJECTIVE
  To re-evaluate the adverse effects of cannabis in the general population and among vulnerable individuals, including those with serious psychiatric disorders.
  
  
  METHODS
  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.
authors.affiliation: Department of Forensic Psychiatry, Institute of Psychiatry, De Crespigny Park, Denmark Hill, London SE5 8AF, UK.
authors.forename: A
authors.initials: A
authors.lastname: Johns
mesh_terms: D000342:Affective Symptoms / Q000139:chemically induced*; D002188:Cannabis / Q000009:adverse effects*; D003072:Cognition Disorders / Q000139:chemically induced; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology / Q000523:psychology*; D011605:Psychoses, Substance-Induced / Q000209:etiology*; D011618:Psychotic Disorders / Q000453:epidemiology; D011619:Psychotropic Drugs / Q000009:adverse effects*; D012307:Risk Factors; D013375:Substance Withdrawal Syndrome / Q000209:etiology
chemical_list: D011619:Psychotropic Drugs