Dual Use of Combustible Cigarettes and E-cigarettes: a Narrative Review of Current Evidence

E-cigarette use (vaping) among adults has increased, and various patterns of concurrent smoking and vaping (i.e., "dual use") have emerged. Understanding dual use is important for mitigating tobacco-related harm. This narrative review summarizes recent research on dual use, including prevalence and types of dual use, sociodemographic and psychiatric characteristics, nicotine dependence, reasons for dual use, harm perceptions, toxicant exposure, trajectories of dual use, and emerging treatments for dual use.Nearly half of e-cigarette users concurrently use cigarettes, and many smoke more frequently than they use e-cigarettes. This is concerning because dual users are exposed to both cigarette and potential e-cigarette toxicants and the data are mixed regarding the ability of e-cigarettes to promote smoking cessation.Further work is needed to identify ways to increase complete smoking abstinence and optimize harm reduction among dual users, including strategies to encourage e-cigarette cessation after stopping smoking.