The Gateway Effect of E-cigarettes: Reflections on Main Criticisms.

Abstract

The recent spread of e-cigarette use has spurred not only enthusiasm about their harm reduction and smoking cessation potential but also concerns about possible risks from long-term use, and stalled cessation through dual use.1 Another main concern is that e-cigarette use is increasing among tobacco-naive youth2 than among only adult smokers who are using them for cessation and expectation of risk reduction.1 With youth smoking at all-time lows in several nations with advanced tobacco control programs,3–5 there are therefore concerns that e-cigarettes may stall or reverse these declines as youth who were likely to never use any form of nicotine become familiar with it, and start experimenting with other forms of nicotine delivery. These concerns were strengthened by the recent publication of a meta-analysis of longitudinal studies showing that e-cigarettes can serve as a gateway to later cigarette smoking among nicotine-naive youth.6 They were also emphasized by the 2018 report of the National Academies of Sciences, Engineering, and Medicine (NASEM),7 which concluded that such studies “provided “strong evidence of plausibility and specificity of a possible causal effect of e-cigarette use on smoking…” with the Committee “consider[ing] the overall body of evidence of a causal effect of e-cigarette use on risk of transition from never to ever smoking to be substantial” (pp. 16–32). By contrast, Public Health England concluded, “Despite some experimentation with these devices among never smokers, e-cigarettes are attracting very few young people who have never smoked into regular use”.8 Given the importance of putative gateway or “catalyst”9 effects in assessing the population impact of e-cigarettes, proponents of e-cigarettes were quick to criticize such evidence and their underlying gateway hypothesis.10–13 In the context of this debate, the gateway hypothesis is adapted to denote the use of less harmful forms of nicotine delivery (eg, e-cigarettes), leading to the use of more harmful ones (eg, combustible cigarettes).7,10–13 We here present and respond to three major criticisms that have been made of e-cigarettes’ gateway potential based on currently available evidence.