title: Onset of opportunity to use cannabis and progression from opportunity to dependence: Are influences consistent across transitions?
abstract: BACKGROUND
  There is a developing body of research looking at cannabis use opportunity, but little research examining timing of opportunity to use cannabis.
  
  
  OBJECTIVE
  Identify factors associated with (1) earlier opportunity to use cannabis and (2) faster progression from opportunity to cannabis dependence.
  
  
  METHODS
  Cross-sectional study of 3824 Australian twins and siblings, measuring age of onset of cannabis use opportunity and DSM-IV cannabis dependence. Survival analysis identified factors associated with faster progression to opportunity or dependence.
  
  
  RESULTS
  Factors associated with both speed of progression to opportunity and dependence were conduct disorder (opportunity HR 5.57, 95%CI 1.52-20.47; dependence HR 2.49, 95%CI 1.91-3.25), parental drug problems (opportunity HR 7.29, 95%CI 1.74-30.62; dependence HR 3.30, 95%CI 1.63-6.69), weekly tobacco use (opportunity HR 8.57, 95%CI 3.93-18.68; dependence HR 2.76, 95% CI 2.10-3.64), and female gender (opportunity HR 0.69, 95%CI 0.64-0.75; dependence HR 0.44, 95%CI 0.34-0.55). Frequent childhood religious attendance (HR 0.74, 95%CI 0.68-0.80), parental conflict (HR 1.09, 95%CI 1.00-1.18), parental alcohol problems (HR 1.19, 95%CI 1.08-1.30) and childhood sexual abuse (HR 1.17, 95%CI 1.01-1.34) were uniquely associated with transition to opportunity. Depressive episode (HR 1.44, 95%CI 1.12-1.85), tobacco dependence (HR 1.36, 95%CI 1.04-1.78), alcohol dependence (HR 2.64, 95%CI 1.53-4.58), other drug use (HR 2.10, 95%CI 1.64-2.69) and other drug dependence (HR 2.75, 95%CI 1.70-4.43) were uniquely associated with progression to dependence.
  
  
  CONCLUSIONS
  The profile of factors associated with opportunity to use cannabis and dependence only partially overlaps, suggesting targeting of interventions may benefit from being tailored to the stages of drug use.
authors.affiliation: Addictions Department, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, England, UK. Electronic address: lindsey.hines@kcl.ac.uk.
authors.forename: Lindsey A
authors.initials: LA
authors.lastname: Hines
authors.affiliation: Addictions Department, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, England, UK.
authors.forename: Katherine I
authors.initials: KI
authors.lastname: Morley
authors.affiliation: Addictions Department, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, England, UK.
authors.forename: John
authors.initials: J
authors.lastname: Strang
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Arpana
authors.initials: A
authors.lastname: Agrawal
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Elliot C
authors.initials: EC
authors.lastname: Nelson
authors.affiliation: School of Social Sciences, University of the Sunshine Coast, Queensland, Australia.
authors.forename: Dixie
authors.initials: D
authors.lastname: Statham
authors.affiliation: QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.
authors.forename: Nicholas G
authors.initials: NG
authors.lastname: Martin
authors.affiliation: Addictions Department, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, England, UK.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Lynskey
mesh_terms: D000328:Adult; D017668:Age of Onset; D001315:Australia / Q000453:epidemiology; D003430:Cross-Sectional Studies; D039721:Diagnostic and Statistical Manual of Mental Disorders; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000175:diagnosis / Q000453:epidemiology*; D008385:Marijuana Smoking / Q000453:epidemiology*; D008875:Middle Aged; D012042:Registries; D012307:Risk Factors; D035781:Siblings; D016019:Survival Analysis; D014427:Twins / Q000706:statistics & numerical data; D055815:Young Adult
keywords: Cannabis; Dependence; Etiology; Opportunity; Risk factors; Substance use; Survival analysis; Transitions
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