First, in contrast to what Stan Glantz is arguing, dual use does not appear to be an "adverse consequence" of e-cigarette experimentation. Instead, it appears to be a positive effect that results in a substantial reduction in cigarette consumption among smokers who would almost certainly not have quit smoking altogether in the absence of electronic cigarettes.

Although the survey approach described above would lead to "invalid" results, I would never argue that survey studies should be thrown out and that we should only be conducting RCTs. My point is that there are strengths and limitations of various study designs, and causal inference is enhanced by having research evidence from multiple study designs. On balance, the strengths and weaknesses balance each other out, leading to a much greater ability to draw valid conclusions.

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