title: Change in cannabis use in the general population: a longitudinal study on the impact on psychotic experiences.
abstract: OBJECTIVE
  To prospectively assess the relationship between cannabis use and psychotic experiences over time.
  
  
  METHODS
  In a longitudinal design, young adults aged 18-27years (N=705) gave online information on cannabis use and completed the Community Assessment of Psychic Experiences (CAPE). These measures were repeated after an interval ranging from six months to five years.
  
  
  RESULTS
  A decrease in cannabis use was associated with a decrease in total psychotic experiences (β=-0.096, p=0.01) after adjustment for a range of potential confounders. An increase in cannabis use was associated with increased positive symptoms at follow-up (β=0.07, p=0.02), but was not significantly associated with increases in Negative and Depression symptom scores, nor with the total number of psychotic experiences.
  
  
  CONCLUSIONS
  In the first study to the association of change in cannabis use and psychotic experiences over time in the general population, we found an association between changes in cannabis use and changes in the frequency of psychotic experiences. While this does not prove a causal relationship between cannabis use and psychosis, our findings are consistent with studies suggesting that cessation of cannabis use may be beneficial in terms of reducing psychotic experiences.
authors.affiliation: Brain Center Rudolf Magnus, University Medical Center Utrecht, Department of Psychiatry, HP. B01.206, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands; Department of Psychiatry, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands; Department of Sexology & Psychosomatic Obstetrics and Gynaecology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: W A
authors.initials: WA
authors.lastname: van Gastel
authors.affiliation: Brain Center Rudolf Magnus, University Medical Center Utrecht, Department of Psychiatry, HP. B01.206, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. Electronic address: a.vreeker@umcutrecht.nl.
authors.forename: A
authors.initials: A
authors.lastname: Vreeker
authors.affiliation: Brain Center Rudolf Magnus, University Medical Center Utrecht, Department of Psychiatry, HP. B01.206, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands; Department of Psychiatry, Tergooi Hospital, Hilversum, The Netherlands.
authors.forename: C D
authors.initials: CD
authors.lastname: Schubart
authors.affiliation: Department of Psychosis Studies, Institute of Psychiatry, King's College, London, UK.
authors.forename: J H
authors.initials: JH
authors.lastname: MacCabe
authors.affiliation: Brain Center Rudolf Magnus, University Medical Center Utrecht, Department of Psychiatry, HP. B01.206, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
authors.forename: R S
authors.initials: RS
authors.lastname: Kahn
authors.affiliation: Brain Center Rudolf Magnus, University Medical Center Utrecht, Department of Psychiatry, HP. B01.206, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
authors.forename: M P M
authors.initials: MP
authors.lastname: Boks
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology*; D008385:Marijuana Smoking / Q000453:epidemiology*; D009426:Netherlands / Q000453:epidemiology; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000453:epidemiology*; D055815:Young Adult
keywords: Cannabis; Psychosis; Psychotic experience; Risk