Progression from marijuana use to daily smoking and nicotine dependence in a national sample of U.S. adolescents.

Background: While it has been demonstrated that smoking cigarettes in adolescence increases the likelihood of progressing to marijuana use, few studies have considered the reverse scenario in which early use of cannabis leads to greater tobacco smoking.

Methods: Participants (n=5963), who had never smoked cigarettes daily by wave I of the National Longitudinal Study of Adolescent Health, were followed 6 years (waves I-III) from adolescence into young adulthood. Measures of marijuana use (lifetime use, monthly use, age at first use), as assessed at wave I within 12-16 (n=3712) and 17-21 (n=2251) year-olds, were separately modeled as predictors of three tobacco-related outcomes: (1) age at onset of daily cigarette smoking, (2) lifetime nicotine dependence, (3) current nicotine dependence.

Results: In the older cohort (17-21-year-olds at wave I), lifetime (>10 times) and past-month marijuana use at wave I were predictive of an earlier initiation into daily cigarette smoking and a greater likelihood of developing nicotine dependence by wave III. Furthermore, age at first use of cannabis was negatively associated with risk of nicotine dependence in the older, but not younger cohort.

Conclusion: After controlling for baseline measures of tobacco smoking and other demographic risk factors, the use of marijuana in adolescence was modestly associated with daily cigarette smoking and nicotine dependence in young adulthood.