Use of Electronic Cigarettes as a Predictor of Cannabis Experimentation: A Longitudinal Study Among German Youth.

INTRODUCTION: Experimentation with e-cigarettes is rising among youth, and there are concerns that e-cigarettes could be a new risk factor for initiating substance use. This study aimed to investigate whether e-cigarette use longitudinally predicts experimentation with cannabis. AIMS AND METHODS: During 2017-2019, a prospective cohort study with an observation period of 18 months was conducted with 3040 students from Germany who had never used cannabis (mean age = 14.8, range: 13-18 years). A multiple Poisson regression was used to investigate whether e-cigarette use was an independent predictor of future cannabis use. RESULTS: Lifetime e-cigarette use was reported by 29.4% of the survey population (n = 894) at baseline, and 17.4% (n = 529) initiated cannabis use during the observation period. Among e-cigarette ever users, the initiation rate was 34.5% compared with 10.4% of never users. Results were robust to adjustment for age, sex, migrant status, type of school, sensation seeking, peer cannabis use, the use of alcohol and conventional cigarettes (ARR = 1.83; 95% CI: 1.48-2.25). Further analyses revealed that the association between e-cigarette use and cannabis experimentation was stronger among youth with low sensation-seeking scores (ARR = .77, CI: .61-.97) and no conventional cigarette use (ARR = .48, CI: .37-.64) at baseline. CONCLUSIONS: E-cigarette use is associated with a subsequent initiation of cannabis use. This association seems to be stronger for youth who have a lower risk for substance use in general. Future studies need to investigate whether this is only true for experimental or also more frequent cannabis use. IMPLICATIONS: The study indicates a prospective association between e-cigarette use and initiation of cannabis experimentation independent of other risk factors. It suggests that e-cigarette use is more strongly associated with cannabis initiation for youth with a lower propensity to use substances (low sensation-seekers and non-smokers).