Neither the survey approach or the RCT approach is perfect. Both have major strengths and significant limitations. The best way to proceed is to conduct both types of studies and to synthesize the results across study designs, keeping in mind the methodological strengths and limitations of each individual study. Only by looking at this totality of the evidence can we draw valid scientific conclusions.

This assertion is based on a new study which found that electronic cigarette use, like smoking, results in reduced levels of exhaled nitric oxide. As Dr. Glantz writes:

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