To date, results from several longitudinal studies indicate that e-cigarette use among nonsmoking youth increases the likelihood of future use of conventional cigarettes. Specifically, the pooled odds ratio (OR) in a recent meta-analysis of studies of adolescents and young adults (aged 14–30) indicates that those who had ever used e-cigarettes were 3.62 times more likely to report using cigarettes at follow-up compared with those who had not used e-cigarettes.