To date, results from several longitudinal studies indicate that e-cigarette use among nonsmoking youth increases the likelihood of future use of conventional cigarettes.5 — 10 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.11 This finding was robust and remained significant when adjusting for known risk factors associated with cigarette smoking, including demographic,
psychosocial, and behavioral
variables such as cigarette susceptibility.