title: Cannabis use is associated with 3years earlier onset of schizophrenia spectrum disorder in a naturalistic, multi-site sample (N=1119).
abstract: BACKGROUND
  Patients with schizophrenia spectrum disorders and substance use may have an earlier onset of illness compared to those without substance use. Most previous studies have, however, too small samples to control for confounding variables and the effect of specific types of substances. The present study aimed to examine the relationship between substance use and age at onset, in addition to the influence of possible confounders and specific substances, in a large and heterogeneous multisite sample of patients with schizophrenia spectrum disorders.
  
  
  METHODS
  The patients (N=1119) were recruited from catchment areas in Oslo, Stavanger and Bergen, Norway, diagnosed according to DSM-IV and screened for substance use history. Linear regression analysis was used to examine the relationship between substance use and age at onset of illness.
  
  
  RESULTS
  Patients with substance use (n=627) had about 3years earlier age at onset (23.0years; SD 7.1) than the abstinent group (n=492; 25.9years; SD 9.7). Only cannabis use was statistically significantly related to earlier age at onset. Gender or family history of psychosis did not influence the results.
  
  
  CONCLUSIONS
  Cannabis use is associated with 3years earlier onset of psychosis.
authors.affiliation: Division of Psychiatry, Haukeland University Hospital, Bergen, Norway. Electronic address: siri.helle@helse-bergen.no.
authors.forename: Siri
authors.initials: S
authors.lastname: Helle
authors.affiliation: Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway; NORMENT K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Norway.
authors.forename: Petter Andreas
authors.initials: PA
authors.lastname: Ringen
authors.affiliation: Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway; NORMENT K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Norway.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Melle
authors.affiliation: Division of Psychiatry, Centre for Clinical Research in Psychosis, Stavanger University Hospital, Norway; Department of Clinical Medicine, University of Bergen, Norway.
authors.forename: Tor-Ketil
authors.initials: TK
authors.lastname: Larsen
authors.affiliation: Division of Psychiatry, Haukeland University Hospital, Bergen, Norway.
authors.forename: Rolf
authors.initials: R
authors.lastname: Gjestad
authors.affiliation: Division of Psychiatry, Haukeland University Hospital, Bergen, Norway; Department of Clinical Medicine, University of Bergen, Norway.
authors.forename: Erik
authors.initials: E
authors.lastname: Johnsen
authors.affiliation: Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway; NORMENT K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Norway.
authors.forename: Trine Vik
authors.initials: TV
authors.lastname: Lagerberg
authors.affiliation: Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway; NORMENT K.G. Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Norway.
authors.forename: Ole A
authors.initials: OA
authors.lastname: Andreassen
authors.affiliation: Division of Psychiatry, Haukeland University Hospital, Bergen, Norway; Department of Clinical Medicine, University of Bergen, Norway.
authors.forename: Rune Andreas
authors.initials: RA
authors.lastname: Kroken
authors.affiliation: Division of Psychiatry, Centre for Clinical Research in Psychosis, Stavanger University Hospital, Norway; Network for Medical Sciences, Faculty of Social Sciences, University of Stavanger, Norway.
authors.forename: Inge
authors.initials: I
authors.lastname: Joa
authors.affiliation: Division of Psychiatry, Centre for Clinical Research in Psychosis, Stavanger University Hospital, Norway.
authors.forename: Wenche
authors.initials: W
authors.lastname: Ten Velden Hegelstad
authors.affiliation: Division of Psychiatry, Haukeland University Hospital, Bergen, Norway; Department of Clinical Psychology, University of Bergen, Norway.
authors.forename: Else-Marie
authors.initials: EM
authors.lastname: Løberg
mesh_terms: D000328:Adult; D017668:Age of Onset; D002188:Cannabis; D005190:Family; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000150:complications* / Q000453:epidemiology*; D009664:Norway / Q000453:epidemiology; D011618:Psychotic Disorders / Q000150:complications* / Q000453:epidemiology*; D012044:Regression Analysis; D012559:Schizophrenia / Q000150:complications* / Q000453:epidemiology*; D012737:Sex Factors; D055815:Young Adult
keywords: Age at onset; Cannabis; Non-affective psychosis; Schizophrenia; Substance; Substance use