Abstract for: Trends in Electronic Cigarette Use and Conventional Smoking: Quantifying a Possible 'Diversion' Effect among U.S. Adolescents

Electronic cigarettes (ECs) have become popular since ~2010, and their impact on conventional smoking is hotly debated. While some fear that ECs act as a “gateway” to nicotine use, others point out their harm reduction potential. A critical, yet understudied, question is whether ECs divert adolescents from conventional smoking. Stock-and-flow structures for cigarette use, EC use, and dual use were modeled, with 'Gateway' and 'diversion' effects increasing dual use, and decreasing cigarette use, respectively. The model was calibrated using data from the US National Youth Tobacco Survey (NYTS). A base-case, counterfactual scenario representing the absence of ECs was estimated by projecting trends calibrated with 2000-2010 smoking prevalence, into 2011-2018. Observed trends in EC and/or cigarette use are more consistent with a net diversion effect than a gateway effect. The magnitude of the net diversion effect is estimated to be 0.74, based on parameter optimization to achieve the best fit with observed data over 2011-2018.ECs may divert adolescents away from conventional cigarette smoking, which is favorable for population-level harm reduction. This is the first study to empirically estimate the potential of ECs to divert from cigarette use.