title: Predictors of age at onset of tobacco and cannabis use in Danish adolescents.
abstract: BACKGROUND
  Early onset of tobacco and cannabis use predicts later substance abuse and risk behaviour and has large health consequences.
  
  
  OBJECTIVE
  The aim of this study was to examine risk factors for the age at onset of smoking and cannabis use among a group of Danish children between 7 years and 18 years of age.
  
  
  METHODS
  Four hundred and eighty randomly selected children and their parents participated in a study about the prevalence of asthma. The study included questions about alcohol, tobacco and cannabis use. The children were interviewed face-to-face while the parents answered a questionnaire.
  
  
  RESULTS
  The age at onset of daily smoking was significantly associated with the adolescents' tendency to binge drink [hazard ratio 4.78, 95% confidence interval (CI) (1.85-12.34), P = 0.001) and to use hard drugs [hazard ratio 2.81, 95% CI (1.03-7.78), P = 0.047], whereas the age at onset of cannabis use was significantly associated with binge drinking [hazard ratio 3.29, 95% CI (1.51-7.20), P = 0.003] and cigarette smoking [hazard ratio 2.51, 95% CI (1.26-5.00), P = 0.009]. There were no significant effect of the parents' smoking and alcohol habits, their socioeconomic or marital status on the adolescent' age at onset of smoking or cannabis.
  
  
  CONCLUSIONS
  This study shows a close connection between adolescent tobacco and cannabis use and alcohol habits. Knowledge of this is important when planning future prevention strategies.
authors.affiliation: Department of Gastroenterology, Hvidovre Hospital, Copenhagen, Denmark.
authors.forename: Ida Kim
authors.initials: IK
authors.lastname: Wium-Andersen
authors.forename: Marie Kim
authors.initials: MK
authors.lastname: Wium-Andersen
authors.forename: Ulrik
authors.initials: U
authors.lastname: Becker
authors.forename: Simon Francis
authors.initials: SF
authors.lastname: Thomsen
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D017668:Age of Onset; D000428:Alcohol Drinking / Q000009:adverse effects*; D000435:Alcoholic Intoxication / Q000453:epidemiology; D002648:Child; D003430:Cross-Sectional Studies; D003718:Denmark; D005260:Female; D006801:Humans; D015994:Incidence; D007407:Interviews as Topic; D008297:Male; D008385:Marijuana Smoking / Q000453:epidemiology*; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology*