title: Risk factors predicting changes in marijuana involvement in teenagers.
abstract: BACKGROUND
  Marijuana use during adolescence has various adverse psychological and health outcomes. It is poorly understood whether the same risk factors influence different stages in the development of marijuana involvement.
  
  
  OBJECTIVE
  To establish which risk factors best explain different stages of marijuana involvement.
  
  
  METHODS
  Data were collected at 2 points using computer-assisted personal interview (wave 1 and wave 2 were separated by 1 year). Twenty-one well-established risk factors of adolescent substance use/abuse were used to predict 5 stages of marijuana involvement: (1) initiation of experimental use, (2) initiation of regular use, (3) progression to regular use, (4) failure to discontinue experimental use, and (5) failure to discontinue regular use. Data were analyzed using logistic regression analysis.
  
  
  METHODS
  Middle school and high school students (N = 13 718, aged 11-21 years) participating in the National Longitudinal Study of Adolescent Health (Add Health).
  
  
  RESULTS
  Three risk factors (own and peer involvement with substances, delinquency, and school problems) were the strongest predictors of all stages. Their combined presence greatly increased risk of initiation of experimental (odds ratio, 20) and regular (odds ratio, 87) marijuana use over the next year. Personality, family, religious, and pastime factors exerted stage-specific, sex-specific, and age-specific influences.
  
  
  CONCLUSIONS
  Assessment of substance, school, and delinquency factors is important in identifying individuals at high risk for continued involvement with marijuana. Prevention and/or intervention efforts should focus on these areas of risk.
authors.affiliation: Division of Psychological Medicine, College of Medicine, Cardiff University, Cardiff, Wales.
authors.forename: Marianne B M
authors.initials: MB
authors.lastname: van den Bree
authors.forename: Wallace B
authors.initials: WB
authors.lastname: Pickworth
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D000328:Adult; D000367:Age Factors; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007604:Juvenile Delinquency / Q000523:psychology; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D002189:Marijuana Abuse / Q000175:diagnosis* / Q000517:prevention & control / Q000523:psychology*; D008960:Models, Psychological; D010379:Peer Group; D011379:Prognosis; D012307:Risk Factors; D012737:Sex Factors; D012917:Social Adjustment