title: Cannabis use and age at onset of symptoms in subjects at clinical high risk for psychosis.
abstract: OBJECTIVE
  Numerous studies have found a robust association between cannabis use and the onset of psychosis. Nevertheless, the relationship between cannabis use and the onset of early (or, in retrospect, prodromal) symptoms of psychosis remains unclear. The study focused on investigating the relationship between cannabis use and early and high-risk symptoms in subjects at clinical high risk for psychosis.
  
  
  METHODS
  Prospective multicenter, naturalistic field study with an 18-month follow-up period in 245 help-seeking individuals clinically at high risk. The Composite International Diagnostic Interview was used to assess their cannabis use. Age at onset of high risk or certain early symptoms was assessed retrospectively with the Interview for the Retrospective Assessment of the Onset of Schizophrenia.
  
  
  RESULTS
  Younger age at onset of cannabis use or a cannabis use disorder was significantly related to younger age at onset of six symptoms (0.33 < r(s) < 0.83, 0.004 < P < 0.001). Onset of cannabis use preceded symptoms in most participants.
  
  
  CONCLUSIONS
  Our results provide support that cannabis use plays an important role in the development of psychosis in vulnerable individuals. Cannabis use in early adolescence should be discouraged.
authors: Department of Psychiatry, Academic Medical Center, University of Amsterdam, the Netherlands.
authors: S
authors: S
authors: Dragt
authors: D H
authors: DH
authors: Nieman
authors: F
authors: F
authors: Schultze-Lutter
authors: F
authors: F
authors: van der Meer
authors: H
authors: H
authors: Becker
authors: L
authors: L
authors: de Haan
authors: P M
authors: PM
authors: Dingemans
authors: M
authors: M
authors: Birchwood
authors: P
authors: P
authors: Patterson
authors: R K R
authors: RK
authors: Salokangas
authors: M
authors: M
authors: Heinimaa
authors: A
authors: A
authors: Heinz
authors: G
authors: G
authors: Juckel
authors: H
authors: H
authors: Graf von Reventlow
authors: P
authors: P
authors: French
authors: H
authors: H
authors: Stevens
authors: S
authors: S
authors: Ruhrmann
authors: J
authors: J
authors: Klosterkötter
authors: D H
authors: DH
authors: Linszen
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D017668:Age of Onset; D001526:Behavioral Symptoms / Q000175:diagnosis / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007406:Interview, Psychological / Q000379:methods; D008297:Male; D002189:Marijuana Abuse / Q000150:complications / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology / Q000523:psychology; D010342:Patient Acceptance of Health Care / Q000523:psychology; D011446:Prospective Studies; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology / Q000209:etiology / Q000523:psychology; D011619:Psychotropic Drugs / Q000627:therapeutic use*; D012307:Risk Factors; D057566:Self Report
chemical_list: D011619:Psychotropic Drugs