The head of the CDC recently talked to the folks at Web MD specifically about e-cigarettes. In what should come as a surprise to no one is that many parallels were wrongly drawn to tobacco cigarettes. Kudos to the website for directly asking about the study that indicates the gateway theory may be a red herring.
First of all, I told you so. Second, wha? Yes, they were older and used to be adolescent, the idea was to see if they grew up to smoke. It's like that old joke of looking for your keys by the streetlight because it's easier to see over there.