title: Cannabis abuse and the course of recent-onset schizophrenic disorders.
abstract: OBJECTIVE
  We sought to examine the relation between cannabis abuse and the symptomatic course of recent-onset schizophrenia and related disorders.
  
  
  METHODS
  A prospective cohort study over a year using monthly Brief Psychiatric Rating Scale assessments.
  
  
  METHODS
  Cannabis-abusing patients (n = 24) were compared with nonabusers (n = 69). Eleven patients were mild and 13 were heavy cannabis-abusing patients.
  
  
  RESULTS
  Significantly more and earlier psychotic relapses occurred in the cannabis-abusing group (P = .03). This association became stronger when mild and heavy cannabis abuse were distinguished (P = .002). No confounding effect of other variables, eg, other street drugs, was found. In all but one patient, cannabis abuse preceded the onset of the first psychotic symptoms for at least 1 year.
  
  
  CONCLUSIONS
  Cannabis abuse and particularly heavy abuse can be considered a stressor eliciting relapse in patients with schizophrenia and related disorders and possibly a premorbid precipitant.
authors.affiliation: Psychiatric Center, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: D H
authors.initials: DH
authors.lastname: Linszen
authors.forename: P M
authors.initials: PM
authors.lastname: Dingemans
authors.forename: M E
authors.initials: ME
authors.lastname: Lenior
mesh_terms: D000293:Adolescent; D000328:Adult; D000553:Ambulatory Care; D015331:Cohort Studies; D015897:Comorbidity; D005260:Female; D005500:Follow-Up Studies; D006760:Hospitalization; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D011379:Prognosis; D011446:Prospective Studies; D012008:Recurrence; D012559:Schizophrenia / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology; D012565:Schizophrenic Psychology