I belatedly realized I should have circulated this more widely. Comments still welcome — a version is under review at a journal at the time of this posting, but there is still time for to improve it based on peer review before that process is completed. The paper expands on the analysis presented in this post.
Abstract: The “gateway” claim, that use of low-risk tobacco products causes would-be nonsmokers to start smoking, is increasingly being invoked in policy discussions. However, the evidence cited as supporting this claim does not distinguish between this claim and competing hypotheses that observed associations are caused by confounding or by smokers attempting to employ tobacco harm reduction. Two recent papers by Glantz and colleagues are claimed by the authors to demonstrate a gateway effect of e-cigarettes causing smoking among youth. The present analysis demonstrates that this conclusion and others drawn by the authors are not supported by their results.