Predictors of age at onset of tobacco and cannabis use in Danish adolescents

INTRODUCTION: Early onset of tobacco and cannabis use predicts later substance abuse and risk behaviour and has large health consequences. OBJECTIVES: 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. CONCLUSION: 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.