title: Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study.
abstract: OBJECTIVE
  To determine whether use of cannabis in adolescence increases the risk for psychotic outcomes by affecting the incidence and persistence of subclinical expression of psychosis in the general population (that is, expression of psychosis below the level required for a clinical diagnosis).
  
  
  METHODS
  Analysis of data from a prospective population based cohort study in Germany (early developmental stages of psychopathology study).
  
  
  METHODS
  Population based cohort study in Germany.
  
  
  METHODS
  1923 individuals from the general population, aged 14-24 at baseline.
  
  
  METHODS
  Incidence and persistence of subthreshold psychotic symptoms after use of cannabis in adolescence. Cannabis use and psychotic symptoms were assessed at three time points (baseline, T2 (3.5 years), T3 (8.4 years)) over a 10 year follow-up period with the Munich version of the composite international diagnostic interview (M-CIDI).
  
  
  RESULTS
  In individuals who had no reported lifetime psychotic symptoms and no reported lifetime cannabis use at baseline, incident cannabis use over the period from baseline to T2 increased the risk of later incident psychotic symptoms over the period from T2 to T3 (adjusted odds ratio 1.9, 95% confidence interval 1.1 to 3.1; P=0.021). Furthermore, continued use of cannabis increased the risk of persistent psychotic symptoms over the period from T2 to T3 (2.2, 1.2 to 4.2; P=0.016). The incidence rate of psychotic symptoms over the period from baseline to T2 was 31% (152) in exposed individuals versus 20% (284) in non-exposed individuals; over the period from T2 to T3 these rates were 14% (108) and 8% (49), respectively.
  
  
  CONCLUSIONS
  Cannabis use is a risk factor for the development of incident psychotic symptoms. Continued cannabis use might increase the risk for psychotic disorder by impacting on the persistence of symptoms.
authors.affiliation: Department of Psychiatry and Neuropsychology, South Limburg Mental Health Research and Teaching Network, EURON, Maastricht University Medical Center, Maastricht, Netherlands.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Kuepper
authors.forename: Jim
authors.initials: J
authors.lastname: van Os
authors.forename: Roselind
authors.initials: R
authors.lastname: Lieb
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Wittchen
authors.forename: Michael
authors.initials: M
authors.lastname: Höfler
authors.forename: Cécile
authors.initials: C
authors.lastname: Henquet
mesh_terms: D000293:Adolescent; D005260:Female; D005500:Follow-Up Studies; D005858:Germany / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D002189:Marijuana Abuse / Q000150:complications* / Q000453:epidemiology; D011605:Psychoses, Substance-Induced / Q000453:epidemiology / Q000209:etiology*; D012307:Risk Factors; D012423:Rural Health; D012959:Socioeconomic Factors; D014504:Urban Health; D055815:Young Adult