title: Premorbid cannabis use is associated with more symptoms and poorer functioning in schizophrenia spectrum disorder.
abstract: Cannabis use disorder is associated with an earlier age at onset and a more severe outcome of schizophrenia spectrum disorders. The role of cannabis use before the onset of illness (premorbid cannabis use) has not been fully investigated. We here examined how amount and type of premorbid cannabis use was associated with the later course of illness including current substance use, symptoms and level of functioning in schizophrenia spectrum disorder.
  
  
  
  We used a naturalistic sample of patients with DSM-IV schizophrenia spectrum disorders with a comprehensive history of illness and substance use. Data on premorbid substance use was obtained from comprehensive self-report. The relationship to outcome was investigated using regression models that included current substance use and premorbid functioning.
  
  
  
  Pre-schizophrenia cannabis use was significantly associated with more severe psychotic symptoms and impaired functioning. Higher levels of premorbid cannabis use were associated with higher levels of current psychotic symptoms. These associations were independent of current substance use and premorbid functioning. Early use of cannabis (age <17 years) was associated with earlier age at onset of psychosis, independently of potential confounders.
  
  
  
  Pre-psychosis cannabis use affects illness outcome in schizophrenia spectrum disorders, and is associated with lower age at onset of psychosis. These findings of independent negative effects of premorbid cannabis use in schizophrenia suggest that a limitation of the general use of cannabis may have beneficial health effects.
authors.affiliation: Division of Mental Health and Addiction,Oslo University Hospital,Oslo,Norway.
authors.forename: P A
authors.initials: PA
authors.lastname: Ringen
authors.affiliation: Department of mental disorders,Norwegian Institute of Public Health,Oslo,Norway.
authors.forename: R
authors.initials: R
authors.lastname: Nesvåg
authors.affiliation: Division of Psychiatry,Haukeland University Hospital,Bergen,Norway.
authors.forename: S
authors.initials: S
authors.lastname: Helle
authors.affiliation: Division of Mental Health and Addiction,Oslo University Hospital,Oslo,Norway.
authors.forename: T V
authors.initials: TV
authors.lastname: Lagerberg
authors.affiliation: NORMENT, K. G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo,Oslo,Norway.
authors.forename: E H
authors.initials: EH
authors.lastname: Lange
authors.affiliation: Division of Psychiatry,Haukeland University Hospital,Bergen,Norway.
authors.forename: E M
authors.initials: EM
authors.lastname: Løberg
authors.affiliation: Department of Psychiatric Research,Diakonhjemmet Hospital,Oslo,Norway.
authors.forename: I
authors.initials: I
authors.lastname: Agartz
authors.affiliation: Division of Mental Health and Addiction,Oslo University Hospital,Oslo,Norway.
authors.forename: O A
authors.initials: OA
authors.lastname: Andreassen
authors.affiliation: Division of Mental Health and Addiction,Oslo University Hospital,Oslo,Norway.
authors.forename: I
authors.initials: I
authors.lastname: Melle
mesh_terms: D000328:Adult; D019969:Amphetamine-Related Disorders / Q000453:epidemiology / Q000523:psychology; D019970:Cocaine-Related Disorders / Q000453:epidemiology / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology / Q000523:psychology*; D008385:Marijuana Smoking / Q000453:epidemiology / Q000523:psychology*; D009664:Norway / Q000453:epidemiology; D011618:Psychotic Disorders / Q000453:epidemiology / Q000523:psychology*; D012559:Schizophrenia / Q000453:epidemiology / Q000503:physiopathology*; D012565:Schizophrenic Psychology; D055815:Young Adult
keywords: Age at onset; cannabis; premorbid; psychosis; schizophrenia