Patterns of Youth Cigarette Experimentation and Onset of Habitual Smoking.

INTRODUCTION: Although research suggests that youth e-cigarette experimentation is associated with later combustible cigarette experimentation, it is unclear how this relates to habitual smoking. This study assesses how minors' patterns of combustible cigarette and e-cigarette experimentation relate to habitual smoking at ages 18-21 years. METHODS: Between November 2016 and May 2017, a cross-sectional, online survey of current and retrospective cigarette use was fielded among individuals aged 18-21 years who had tried combustible cigarettes or e-cigarettes (n=1,424). Logistic regressions tested how experimentation patterns prior to age 18 years related to two indicators of current habitual smoking: daily smoking and current established smoking (past 30-day use among those who had smoked ≥100 cigarettes). RESULTS: Respondents who first tried combustible cigarettes or e-cigarettes as minors (n=1,096) were more likely to be current established users (64%) than those who first experimented at ages 18-21 years (41%). Experimentation patterns in individuals aged <18 years beginning with combustible cigarettes were the most predictive of later smoking. Relative to those who first experimented at ages >17 years (n=328), trying only combustible cigarettes as a minor yielded a 175% increase in one's odds of being an established smoker (AOR=2.75, 95% CI=1.99, 3.79) and a 161% increase for daily smoking (AOR=2.61, 95% CI=1.75, 3.90). Trying combustibles and then e-cigarettes yielded sizable increases in both habitual smoking measures, whereas trying e-cigarettes before combustibles yielded smaller effects. Trying only e-cigarettes as a minor yielded a 78% decrease in both outcomes, relative to those who did not try either product as minors. CONCLUSIONS: Minors who tried combustible cigarettes were more likely to be habitual smokers at ages 18-21 years than those who tried e-cigarettes alone.