title: Association between cannabis and psychiatric hospitalization.
abstract: OBJECTIVE
  To investigate the relationship between cannabis use and mental health.
  
  
  METHODS
  A cross-sectional analysis in a sample of 17 698 individuals with a mean age of 22 years (SD: 4.2). Participants provided information on the amount and initial age of cannabis use and history of psychiatric hospitalizations through a web-based questionnaire. To quantify Δ(9) -tetrahydrocannabinol exposure, we operationalized cannabis use as the amount of money spent on cannabis per week over the last month. The odds ratio of having a history of psychiatric hospitalizations was the primary outcome measure.
  
  
  RESULTS
  We found a dose-response relationship between the amount of cannabis use and the odds for psychiatric hospitalization. Adjusted odds ratios for hospitalization increased with the amount of cannabis consumed from 1.6 (95% CI: 1.1-2.3) in incidental users to 6.2 (95% CI: 4.3-8.9) in heavy users (>€25/week). Our data suggested that concomitant drug use was an intermediate factor. Exposure to cannabis before the age of 12 years was found to carry a 4.8 (95% CI: 2.9-7.8) times increased odds for past psychiatric hospitalizations.
  
  
  CONCLUSIONS
  We conclude that early and heavy uses of cannabis are each and independently associated with poor mental health in its users.
authors.affiliation: Rudolf Magnus Institute of Neuroscience, Department of Psychiatry, University Medical Center, Utrecht, The Netherlands. c.schubart@umcutrecht.nl
authors.forename: C D
authors.initials: CD
authors.lastname: Schubart
authors.forename: M P M
authors.initials: MP
authors.lastname: Boks
authors.forename: E J
authors.initials: EJ
authors.lastname: Breetvelt
authors.forename: W A
authors.initials: WA
authors.lastname: van Gastel
authors.forename: R H H
authors.initials: RH
authors.lastname: Groenwold
authors.forename: R A
authors.initials: RA
authors.lastname: Ophoff
authors.forename: I E C
authors.initials: IE
authors.lastname: Sommer
authors.forename: R S
authors.initials: RS
authors.lastname: Kahn
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D003365:Costs and Cost Analysis; D003430:Cross-Sectional Studies; D003625:Data Collection; D013759:Dronabinol / Q000008:administration & dosage / Q000009:adverse effects / Q000191:economics; D005260:Female; D006213:Hallucinogens / Q000008:administration & dosage / Q000009:adverse effects / Q000191:economics; D006778:Hospitals, Psychiatric / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000191:economics / Q000628:therapy*; D008603:Mental Health; D009426:Netherlands; D016017:Odds Ratio; D010359:Patient Readmission / Q000706:statistics & numerical data*
chemical_list: D006213:Hallucinogens; D013759:Dronabinol