Three years ago, Thomas Frieden, director of the U.S. Centers for Disease Control and Prevention (CDC),warned that "many kids are starting out with e-cigarettes and then going on to smoke conventional cigarettes." That fear is one of the main justifications for the CDC's hostility toward vaping and the Food and Drug Administration's onerous new e-cigarette regulations, which are expected to cripple the industry. Yet there is no evidence that Frieden's claim is true and considerable evidence that it's not, especially since smoking rates among teenagers have fallen to record lows even as more and more of them experiment with vaping. Two new studies cast further doubt on the idea that e-cigarettes are a "gateway" to the real thing.
Frieden and other e-cigarette alarmists make much of the fact that the percentage of teenagers who report vaping has risen dramatically in recent years. They like to focus on the percentage of teenagers who have ever tried e-cigarettes and the percentage who have used them in the last month, without asking how many are experimenters or occasional users and how many are daily vapers—the sort who might get hooked on nicotine and eventually progress to conventional cigarettes. It turns out there's a good reason for the CDC's lack of curiosity on this point: Survey data show that few teenagers who have never smoked use e-cigarettes and that even fewer do so on a regular basis.
"Many fear that e-cigarette use by non-smoking students will lead many to nicotine addiction and subsequent cigarette smoking," notes University of Michigan health economist Kenneth Warner in an American Journal of Preventive Medicine article published last month. But based on data from the Monitoring the Future Study (MTF), which surveys students in the eighth, 10th, and 12th grades, Warner finds that "non-smoking high school students are highly unlikely to use e-cigarettes" and even less likely to use them regularly. Among the 12th-graders who had never tried conventional cigarettes, 94 percent had not used an e-cigarette in the previous month. Among the never-smokers who reported using e-cigarettes in the previous month, 60 percent used them on only one or two days. Less than 1 percent of never-smokers had vaped on 20 or more days in the previous month.
The MTF numbers, which are similar to the findings of British surveys, suggest it is quite unlikely that "many kids are starting out with e-cigarettes and then going on to smoke conventional cigarettes," because nonsmokers rarely use e-cigarettes often enough to develop a nicotine habit. Another point Warner emphasizes makes Frieden's claim even less plausible: "A large proportion of students use e-cigarettes containing no nicotine." Warner cites a 2014 study that found most never-smoking Connecticut teenagers who vaped used nicotine-free e-liquid.
The significance of that point is underlined by another recently published analysis of MTF data. Richard Miech and three of his colleagues at the University of Michigan's Institute for Social Research (which conducts the survey) report in the journal Tobacco Control that nearly two-thirds of teenagers who have tried vaping consumed "just flavoring" the last time they did it. "Nicotine use came in a distant second," Miech et al. write, "at about 20 percent in 12th and 10th grade and 13 percent in 8th grade." The other options were marijuana and "don't know."
The MTF data indicate that the more frequently teenagers vape, the more likely they are to vape nicotine. Among high school seniors, 47% of those who had vaped six or more times in the previous month reported consuming nicotine, compared to 23 percent of those who had vaped one to five times in the previous month. But "in no case did the prevalence of nicotine vaping reach 50% or greater." In other words, "the majority of US youth who use vaporisers and e-cigarettes do not vape nicotine," a fact that "challenges many common assumptions and practices."
Consider the CDC's practice of counting vaping as "tobacco use," which leads it to claim there has been "no decline in overall youth tobacco use since 2011," even though that is clearly not true. It was already absurd to pretend teenagers were using tobacco when they weren't, especially since the CDC used that inaccurate terminology to imply that the rising popularity of vaping somehow cancels out the health gains from the continuing decline in smoking, a far more dangerous habit. Now that it's clear the typical adolescent vaper is not even using nicotine, the CDC cannot assume any chemical connection between e-cigarettes and tobacco. In fact, as Miech et al. note, even calling e-cigarettes "electronic nicotine delivery systems" (as both the CDC and the FDA do) is misleading, at least in the context of adolescent vaping.
The researchers point out that counting every vaper as a tobacco user doubles the supposed prevalence of tobacco use among 12th-graders and nearly triples it among 10th- and eighth-graders. If vapers are counted as tobacco users only when they vape nicotine (still a dubious maneuver), the effect is much less dramatic. "If vaporiser users are considered nicotine users only if they last vaped nicotine in the last 30 days," Miech et al. say, "then national estimates of nicotine prevalence increase by a much smaller percentage of 23–38 percent across the three grades," compared to the increases of 100 percent to 200 percent seen with the CDC's method.
As you might expect, never-smokers are less inclined to use e-fluids containing nicotine than current or former smokers are. But even if we ignore that difference, the MTF results indicate that only one-third of adolescent vapers are vaping nicotine. That share rises to almost one-half (47 percent) among teenagers who vape six or more times a month. If you multiply that percentage by the 0.7 percent of never-smokers who (according to Warner's study) report vaping on 20 to 30 days in the previous month, you have about 0.3 percent of nonsmokers who are vaping nicotine often enough that they might develop a long-term habit.
If some of those teenagers decide, for whatever mysterious reason, that they'd rather get their nicotine from a source that is smellier, less comfortable, and a lot more dangerous, that would be a pretty rare phenomenon. And even then, it would be impossible to say with any confidence that those same teenagers never would have smoked if e-cigarettes did not exist. At the same time, some of the never-smokers and many of the former smokers who become regular vapers might otherwise be smoking and therefore facing much bigger health risks.
"Cross-sectional studies such as NYTS [National Youth Tobacco Survey] and MTF cannot determine whether the association between concurrent growth in e-cigarette use and reduction in smoking among students is causal or coincidental," Warner writes. "Nor can they assess whether there is a gateway effect from vaping to smoking." It's true that such studies cannot definitively answer the question of whether the availability of e-cigarettes has hastened or retarded the decline in adolescent smoking. Maybe smoking rates among teenagers would have fallen even faster if e-cigarettes had never been introduced.
But probably not. Warner notes that in 2014, following three years in which adolescent experimentation with e-cigarettes exploded, "The MTF data indicated the largest annual percentage decline in smoking in the nearly 40-year history of the survey." That welcome development may surprise you if you've been listening to the CDC.
This article originally appeared at Forbes.com.