The study concluded that: "e-cigarettes generate smaller changes in lung function but similar nicotinergic impact to tobacco cigarettes."

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.

The problem is that in this cross-sectional study, there is no way to determine the direction of the observed relationship.

"Smoking is not uniformly more hazardous than simply taking an exam."

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