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Teen Vaping Part One

Should We Be Worried About Teen Vaping? An In-Depth Look at the Facts and the Arguments

The issue of teen vaping is controversial, to say the least. It seems like every other week a story claims that vaping is addicting teens who’ve never smoked, and that those teens are more likely to progress to smoking cigarettes in the future.


Youth smoking is something that basically everybody – vaping advocates and detractors alike – wants to stop, and so gateway claims are used to justify placing restrictions on e-cigarettes. Even if vaping isn’t that bad, the argument goes, if it leads to smoking then we need to stop youth from vaping however we can. 


The Surgeon General’s report on youth e-cigarette use is a perfect example of this line of reasoning. After outlining the evidence, Vivek Murthy and the other authors discuss several changes to policy intended to reduce the appeal of e-cigarettes to youth.


For vaping advocates, these claims and recommended policies – like raising the taxes on e-cigarette products or banning specific flavors – are obviously unwelcome. They reject the evidence presented that supposedly shows that vaping is a gateway to smoking, often claiming that the fact that the youth smoking rate has been declining rate since vaping became more popular shows that the concerns are unfounded.


If you aren’t firmly entrenched in one camp or the other, this back-and-forth of claim and counter-claim can be tough to navigate. Short of picking through the data with a fine-toothed comb, how can you work out if the pro-vapers or the anti-vapers have it right? How can you work out if either of them is right?


One thing that makes this whole issue so complicated is that there are two sides to this debate. Firstly, there is the scientific debate. Do many teens who don’t smoke start vaping? Are they really more likely to progress to smoking if they vape?


Secondly, there is a more ideological, political side to the debate. Is it right to do anything that could be seen as promoting vaping for adult smokers if it means non-smoking teens will be more likely to pick up the habit? Shouldn’t we be trying to get adults to quit nicotine entirely and teens to never start using it? Or should we be pragmatic about vaping, and acknowledge that while it isn’t perfect, adults or teens vaping is better than them smoking?


To get to the bottom of the scientific issues, we’ve looked through the evidence on the issue, and caught up with two researchers in the field: Carl V. Phillips, who wrote an interesting paper on gateway effects and runs the blog Anti-THR Lies, and Michael Siegel, who runs the The Rest of the Story blog and is currently a professor at the Boston University School of Public Health.


And to delve into the more ideological and political issues, along with Michael and Carl, we caught up with Nick “Grimm” Green, a reviewer who you can find at and on YouTube, Morten Moe, a reviewer and blogger over at the Vaping Giraffe, and Steve K., who runs the blog Steve K.’s Vaping World.


This post is split into two parts. First, we take on the scientific issues surrounding the youth vaping and gateway debates, and then in the companion post, we take a look at the rhetoric, ideology and politics that drive the discussion.


Teen Vaping, Part 1: A Gateway to Bad Science


The Surgeon General’s Report on Teen Vaping: Did Vivek Murthy Put Politics Before Science?


The Surgeon General’s report was released late last year and is quickly becoming the Bible of youth vaping claims. Like the landmark reports on smoking and lung cancer and second-hand smoke in the last half-century or so, the report is meaty and gives the impression of being a comprehensive analysis of the evidence on the topic. However, the report isn’t quite as robust as it may seem.


I asked Carl Phillips what he thought of the report’s treatment of the evidence, and the response definitely didn’t pull any punches:


Carl V. Phillips - Anti THR LiesFaux credulous.


That is, the authors pretended to believe basically any bit of (what they would consider) bad news that was asserted by anyone. I say “pretended” and “faux” because, while they are not exactly serious scientists, it seems unlikely the authors are really are so dim as to believe all that. This is reinforced by the fact that they did not seem to believe any of the analysis that disputes those claims.


This is standard and predictable for “official” reports (in this field and most others): A political actor decides what the message is going to be, based on political goals, and then commissions a report that is designed to support the thesis. The authors may have a bit of independence, but are rarely at liberty to contradict the chosen message and, in any case, are selected because they have already demonstrated they endorse the politically-motivated conclusions.

‘– Carl V. Phillips (Anti-THR Lies)


This is hardly a glowing assessment of the report, but it’s hard to read-through the main conclusions presented and assume the report is going to be completely unbiased. Even simple issues are mischaracterized in order to further a political position, as Michael Siegel adds:


Michael Siegel - the Rest of the StoryThe Surgeon General was very misleading to the public because he characterized vaping as a form of “tobacco use.” This is deceptive because electronic cigarettes do not contain any tobacco. It is not true that vaping is a form of tobacco use. The Surgeon General indicated that vaping is the predominant form of tobacco use among youth. This is false. Vaping is not a form of tobacco use. I think the net effect of the report was to lump e-cigarettes in with real ones. This completely undermines the public’s appreciation of the unique hazards associated with combusted tobacco.

– Michael Siegel (The Rest of the Story)


And it isn’t just Phillips and Siegel that take issue with the report. A comment to the Science Media Centre from Peter Hajek (who directs the Tobacco Dependence Research Unit at Queen Mary University of London) reads:


The new US report’s conclusions do not tally with what the actual data show. It is simply not true that e-cigarettes are a tobacco product or that vaping lures children to smoking or that it creates dependence in non-smokers. The prevalence of smoking among young people is at all time low and regular use of nicotine containing e-cigarettes among never-smokers is extremely rare. On-going vigilance is needed, but so far, e-cigarettes have acted as a gateway away from smoking, for adults and adolescents alike.

– Peter Hajek


Despite this scathing criticism from much of the scientific community, the report’s conclusions were roundly repeated in the media, with headlines like “Surgeon General sounds the alarm on teens and e-cigarettes” hitting high-profile news outlets and being shared widely around social media.


But this is par for the course. Any piece of research that so much as hints that vaping could be a gateway to smoking is leapt on immediately and even completely unjustified conclusions find themselves repeated until they become lodged in the public consciousness. A report from the Surgeon General is bound to generate headlines, and all the more so if it hits on a hot-button topic like teen vaping and the possibility it serves as a gateway to smoking.


The Facts About Teen Vaping and Whether Vaping is a Gateway to Smoking


This all raises the questions: why did the Surgeon General’s report attract so much criticism? What does the evidence really say about the gateway effect and teen vaping?


The Gateway From Vaping to Smoking: A Run-Through of the Claims


Before we look at the evidence on the issue of teen vaping and whether vaping leads teens into smoking, it makes sense to get a clear picture of what is being claimed. Different versions of the claim appear in various places, but anti-vaping campaigns like Still Blowing Smoke provide a good example of the key claims made:


1) E-liquid flavorings make teens more likely to try vaping.

2) E-cigarette companies market to teens.

3) Large numbers of non-smoking teens are starting to vape.

4) Non-smoking teens who try vaping get addicted to nicotine. 

5) The now-addicted teens progress to smoking cigarettes.


Although there are many ways each of these points could be expanded, and there are alternative ways are putting forward the “gateway” case, this covers the key aspects of the narrative. The last three points are really the crucial ones, but the first two are so widely offered as explanations that they have a clear role in the claims made.


Claim 1: E-Liquid Flavorings Make Teens More Likely to Try Vaping


The first claim is one of the most commonly-encountered points about youth vaping. Ordinarily, it’s presented and responded to without evidence. “Bubble gum e-liquid appeals to kids,” says a group like the Campaign for Tobacco-Free Kids, and the response from vapers is “adults also like flavors! People don’t get all angry about flavored vodka!”


But is there any evidence we can turn to instead?


The most commonly-cited study on the topic comes from early 2015, and it compared teen non-smokers with adult smokers when it comes to flavor preferences. A bunch of flavors – for example, gummy bear and whisky – were paired with either e-cigarettes, bottled water or ice cream, and then the participants were asked to rate their interest in trying the product.


The results showed that teen non-smokers were much less interested in vaping than adult smokers, regardless of the flavor offered. Oddly, the e-juice they expressed most interest in was single malt scotch flavor.


However, there are many other studies relevant to the issue too. Many of them show that young vapers are more interested in sweet flavors than tobacco ones, but along with this, others show that most vapers (adult or youth) prefer these flavors to tobacco ones. Particularly importantly, one study found that high school students who were smokers were the most likely to have tried and to prefer sweeter flavors, compared to the never-smokers.


All of this research underlines what should be a fairly obvious fact: things that taste like chocolate or something else sweet have a broader appeal than things that taste like tobacco. This is true for teens just like it’s true for adults, and it’s true for never-smokers just like it’s true for smokers.


But there are other factors that motivate the decision to vape. One example study is often cited because it found that 81.5 % of teen vapers said “I use the product because they come in flavors I like.” This has issues of its own – it was a yes-no question, so of course if you vape you’re likely to say “yes I enjoy the flavors” (discussed in more detail here) – but what’s often forgotten are the other reasons given. In particular, 79 % said they vaped because it’s less harmful to them, and 78 % said they did so because it’s less harmful to others. If you combine these responses to give one result for harm reduction reasons, regardless of who the harm is reduced for, almost 90 % vaped for harm reduction purposes.


On the whole, it seems there are more important reasons teens vape than for the flavors. Although the flavors do appeal to teens, they appeal to adults too, and there is no evidence whatsoever that teens who don’t smoke will start to vape specifically for the flavors.


Michael Siegel agrees that e-juice flavors appeal to youth, but crucially stresses the role they play for adult smokers too:


Michael Siegel - the Rest of the StoryI think it is quite clear that the flavors are one factor that makes vaping appealing to youth. However, it must be remembered that the very same flavors are what make vaping appealing to adult smokers as well. If we get rid of the flavors, we may reduce youth vaping, but we’ll also increase adult smoking.



– Michael Siegel (The Rest of the Story)




And he’s right. A survey of vapers found that the vast majority classed flavors as “important” or “very important” for quitting smoking with e-cigarettes. While most of the studies cited above are eager to recommend limiting the available flavors to reduce the appeal of vaping to teens, they don’t consider the likely negative effect it would have on adults trying to quit and avoid relapse by vaping. Doing the math on this wouldn’t be easy, but that’s the cost-benefit analysis that would have to be conducted to even start to justify a move to ban flavors.


 Claim 2: E-Liquid Companies Market to Teens


This claim is much easier to address because it is rarely – if ever – attempted to be supported by evidence. The Surgeon General’s report has a long section on e-cigarette marketing, but presents no evidence that vaping companies purposefully market to youth. It cites research showing that teens see ads for vaping devices, but it would be hard to put ads out there without any young people seeing them.


There are a couple of studies mentioned in the report that do suggest that vaping ads may encourage smoking. One looked at National Youth Tobacco Survey (NYTS) data and found an association between reporting having seen e-cig ads and having tried one. This is pretty flimsy evidence, though, because you’d expect that people more interested in vaping or who’ve already vaped are more likely to remember seeing ads.


The other was a randomized trial, which offers better evidence that seeing ads could have an effect, but the difference was tiny. Out of the teens who didn’t see the ads, 92 % said they wouldn’t try an e-cig soon, but this only reduced to 88 % for those who saw the ads. However, they saw four ads back to back; far from a realistic scenario.


Overall, there is no evidence whatsoever that e-cigarette companies are targeting teens with advertisements. This makes sense, because advertising to minors as a company in such a heavily scrutinized industry would basically be asking for problems. Plus, even when teens do see ads, the effect seems to be tiny.


Claim 3: Large Numbers of Non-Smoking Teens Are Starting to Vape


This is where the claims start becoming directly relevant to the gateway issue, and where the evidence for them starts to really fall to pieces. Most of the time, people making this claim use data from the NYTS, which has shown rising teen use of e-cigarettes since it started collecting data on them.


The most recent data (from 2015) shows that about 16 % of high school students were classed as “current vapers,” compared to 1.5 % in 2011. But this isn’t “current” vaping in the way you’d think: it’s actually the number of students who’d vaped in the 30 days prior to the survey. If you just focus on the ones who’ve never smoked, the number classed as “current” vapers even by this broad definition shrinks dramatically.


But the big problem is much simpler. Vaping on one day of the last month doesn’t make you a “current” vaper. Really, what people think of when you say someone is a current vaper is somebody who regularly vapes, and still does so at the time of the survey. The good news is that the NYTS does ask about how often they vaped. Unfortunately, this is never reported when the results are first released; you have to wait several months before you can dig into the numbers and get the details.


But the data does get released eventually. In 2015, there were 13,681 students in the survey who’d never smoked a cigarette. Of these, just 1.1 % had vaped on 6 or more days out of the past 30. If you just focus on the never-smokers who’d vaped on 20 or more days, this figure shrinks dramatically to 0.27 %, or just 37 students out of almost 13,700 never-smokers. By focusing on regular vaping, the supposed problem shrinks so quickly it makes your head spin.


Going from this basic data to a claim that e-cigarettes are a gateway to smoking is even more problematic, as Michael Siegel pointed out when I spoke to him:


Michael Siegel - the Rest of the StoryWhile e-cigarette use has skyrocketed among youth, smoking rates have continued to plummet. This is not consistent with the hypothesis that vaping is a gateway to smoking. In fact, the evidence indicates the opposite. Vaping appears to be displacing the smoking culture among youth. It is further de-normalizing smoking, rather than re-normalizing smoking. The current evidence shows that there are very few nonsmoking youth who experiment with e-cigarettes and then become regular vapers, much less progress to become regular smokers. In fact, a recent study published in Tobacco Control could not find a single youth (out of a sample of 350) who progressed from being a nonsmoking recent vaper to a current cigarette smoker.

– Michael Siegel (The Rest of the Story)


Claim 4: Non-Smoking Teens Who Try Vaping Get Addicted to Nicotine


This is where the gateway hypothesis really starts to sink it’s teeth in. A key part of the logic of the claim is that nicotine addiction is what drives the progression from vaping to smoking. Without addiction, you could argue that the act of vaping is similar enough to the act of smoking that it would make teens progress from one to the other, but this is tenuous at best.


In a nutshell, the addiction element is really important. Unfortunately, the NYTS doesn’t ask about whether the teens who vaped consumed nicotine. However, the Monitoring the Future survey does. In the 2016 survey, it found that just a quarter of the teens who’d tried vaping had knowingly used nicotine (and about another 6 % said they “didn’t know”). In other words, the vast majority of teen e-cigarette users didn’t consume nicotine.


More information on this point could easily be even more devastating for the gateway hypothesis. The question is: how many of the never-smoking teens who vaped consumed nicotine? We don’t know, but every implication is that it won’t be many of them.


Claim 5: The Now-Addicted Teens Progress to Smoking Cigarettes


This is the big point. There is a problem right away in that the two previous claims don’t hold much weight, but let’s ignore that for the moment. The question is: do never-smoking teens who use e-cigarettes end up smoking regularly? Is vaping a gateway?


Michael Siegel responds:


Michael Siegel - the Rest of the StoryThere is no evidence that vaping is a gateway to smoking. It is difficult to find youth who started out as nonsmokers, tried vaping, and then became addicted to vaping before progressing to become addicted smokers. The evidence all points in the other direction. Vaping culture appears to be displacing the smoking culture, not propping it up.


– Michael Siegel (The Rest of the Story)


This is simple enough. His comments are also backed up by analyses of the studies which are claimed to support the gateway hypothesis. Typically, these look to see if teens who’ve vaped at least once go on to smoke at least once, and usually they find that there are some youth who progress from vaping to smoking in this way. However, the numbers are always very low (because, as we’ve learned, vaping among non-smokers is rare), and most people think of the gateway effect as referring to regular vaping and regular smoking, not “at least once” for both.


One recent study is a great example of the problems with most gateway studies. Firstly, it makes the mistake of focusing on vaping and smoking “at least once” instead of regularly. Secondly, it doesn’t adequately consider whether or not the teens who progressed to smoking from vaping would have started smoking anyway. And thirdly, as Michael Siegel points out in a blog post, the number of non-smoking teens who’d vaped and then progressed to smoking was pathetically low: just four participants.


This is just one example of many, and the short version is that all of the evidence on the topic sufferers from similar – and in many cases, more obvious – issues. Another example is a 2014 study from Stanton Glantz. This basically found an association between vaping and smoking at a single point in time, with no indication which came first nor anything that could establish that one caused the other. In fact, this study could equally validly be interpreted as showing the exact opposite: that teen smokers switch to vaping for harm reduction purposes.


Many studies on the topic are better than this, but if you realize that it takes a lot more than just “tried vaping then tried smoking” to establish a gateway, then you understand the issues with most of the studies claiming to find a gateway.


Getting Technical: A Clear Hypothesis and the Problem of Plausibility


Carl V. Phillips’ paper on the limitations of the evidence claiming that vaping is a gateway to smoking essentially concludes that none of the evidence we have is enough to answer the question one way or another. I asked him if this was a fair reading, and he responded with an important clarification that gets right to the heart of what it means to say vaping is a gateway to smoking:


Carl V. Phillips - Anti THR LiesYou actually have to step it back a bit and ask “what question?” If the hypothesis is “there has been one gateway case ever”, let alone “there will be a gateway case eventually”, then the answer is undoubtedly “yes”, and no evidence is really needed. There are enough exposed at-risk individuals (i.e., those who could become a gateway case and who try vaping) that this falls into the “if it is not impossible then it is inevitable” zone. This is in spite of the fact that we should not expect this gateway effect to happen much, for reasons I go into in the paper.


By contrast, if the hypothesis is “vaping causes everyone who does it to start smoking within a week” then it is pretty easy to disprove with available evidence. If it is “vaping causes many people to become smokers ten years later”, then there it is difficult to imagine any possible evidence that could inform it. I trust you see my point.


So we have to start by specifying what seems to be a reasonable version of the claim. We have to do it since the proponents of the claim never actually define what they are claiming. It seems reasonable to go with something like “regular vaping causes 10% of the would-be nonsmokers who do it to become smokers within two years.” Then your conclusion is right: It is theoretically possible to assess this scientifically, but no evidence we actually have should move our prior belief about whether that is true by very much.

– Carl V. Phillips (Anti-THR Lies)


The point that “the proponents of the claim never actually define what they are claiming” is absolutely central to going beyond the basics of the gateway claim. In science, you need a clear, testable hypothesis. You need a way to formulate the proposal you’re making so that it can actually be shown to be false.


For the gateway claims that are so widespread in the vaping debate, no such attempt is made. Even if there was really high-quality evidence on the topic, proponents could always move the goalposts and say something like Carl’s example – “vaping causes many people to become smokers ten years later” – and say that the evidence just isn’t long-term enough. This is essentially why Public Health England went so far as to say that gateway terminology be abandoned altogether until a clear definition is provided.


And then there is the all-too-rarely raised issue of plausibility. It’s simply assumed that vaping will lead to smoking, as Carl also points out:


Carl V. Phillips - Anti THR LiesGateway proponents have tricked everyone, including their critics, into not questioning the underlying premise that it is reasonable to expect vaping to often cause smoking. In reality it seems rather unlikely. While this is a little more plausible than the original “cannabis use causes opioid/cocaine/etc. use” version of the gateway claim, it still makes only a tiny bit more sense than claiming that vaping causes risky sexual behavior. 


– Carl V. Phillips (Anti-THR Lies)


Some bloggers do question this, though, and Clive Bates in particular has done a great job of it. In a blog post on the topic, he asks (among other pertinent questions):


  • Why would someone who wouldn’t otherwise have smoked decide to vape but not try smoking?

  • Why would they then decide that they want to progress from a clean, practically harmless, diverse, customisable, non-pariah product into something harmful, dirty, messy anti-social etc? It would be like going from colour TV to black and white; word processor to hand writing. Most smokers express delight at the switch from cigs to e-cigs.

  • What is the plausibility that someone would only experiment with e-cigs but not cigs – surely kids are trying a bit of everything?

  • Maybe nicotine addiction grips them? But if they were inclined to nicotine addiction, why wouldn’t they discover that cigarettes were for them from the outset?

  • Maybe they are lured in because e-cigs are safer? But if fear is a factor (unlikely anyway) why would they switch to something more dangerous?

— Clive Bates (The Counterfactual)


I struggle to see how anybody could come up with satisfactory answers to these questions that would suggest a vaping-to-smoking gateway is likely to be a big concern. The cold hard truth of the matter is that switching from vaping to smoking would be counter-intuitive and downright bizarre.


Getting More Technical: Confounding Variables and How to Actually Investigate Gateway Effects


At this point, the gateway hypothesis is always pretty much dead in the water, having never been adequately put together in the first place and with almost every component part crumbling under scrutiny. But that isn’t the end of the problems.


I asked Carl V. Phillips what he thought the biggest issues with the studies we have so far are, and as well as pointing out the issues with formulating a clear hypothesis (as discussed above), he made several really important points drawn from his academic work on the topic. While I don’t want to get into the specifics too much (Carl will be releasing his full responses as a blog post after this is published, and I’d recommend reading it all if you want to understand the science behind gateway effects), there is one point in particular that is really important.


He starts by making a classification. When you’re looking at something like a gateway claim, you have an exposure – in this case, trying vaping – and the outcome – starting to smoke. It’s implausible that everybody exposed will have the outcome, because people respond to exposures differently. Carl classifies the possible response types as follows:


  • Immune – These people won’t have the outcome even if they’re exposed. In other words: they won’t start smoking even if they do try vaping.
  • Doomed – These people will have outcome whether they’re exposed or not. These people will start smoking eventually, whether they vape or not.
  • Protective – These people will have the outcome, unless they’re exposed. These people would start smoking if they don’t vape, but if they do vape, they’ll stick to it rather than progressing.
  • Causal – These people won’t have the outcome, unless they’re exposed. These people wouldn’t smoke, but would start smoking if they try vaping. These are the “gateway” cases.


If you think about these four response types, the problems with much of the evidence claiming that e-cigs are a gateway to smoking becomes clear. Carl continues:


Carl V. Phillips - Anti THR LiesThe unknown proportions of doomed and immune types, in particular the different mix in the exposed and unexposed populations (known as confounding), means that most statistics cited as suggesting a gateway effect offer no such evidence. That is, we can be sure there is an excess of doomed-to-smoke types among vapers (as compared to never-vapers), and there is little doubt that this disparity dwarfs any actual gateway effect. Thus, if response type is not thoroughly measured or controlled for (and it never is), it is simply not possible to detect the gateway effect. Any association between the exposure and the outcome is plausibly explained by confounding; since there is no estimate of how much confounding there is, it is impossible to know if the association represents any causal relationship above and beyond the confounding.


Cutting the other way, if there are any protective types in the population (and there undoubtedly are), that will mask any gateway effect. So if there were no confounding, the association would be a measure of the net of causal types minus protective types. If there is a sufficient proportion of protective types, it would mean the net effect of vaping is to reduce smoking in the particular population. But this does not mean there is not also a gateway effect (i.e., there could still be some exposed causal types).

–  Carl V. Phillips (Anti-THR Lies)


In other words: we can be pretty sure that vapers are more likely to be doomed-to-smoke than non-vapers, and we can be pretty sure that some would-be-smokers will be stopped by the availability of vaping (protective types). The first group would make vaping look like it caused the smoking, but we know they’re doomed-to-smoke regardless. The second group would muddy the waters more: they’re diverted from smoking by vaping, and so would lead to less smoking than we’d have seen otherwise.


Without knowing how many of each of these there are, how can we be sure how many true “causal” cases there are? How can we be sure that when smoking rates go down as vaping rates go up, this isn’t just because more youths are protected from starting to smoke than are caused to smoke by trying vaping? There is a tangled web of causality and reverse-causality, not to mention the issue of groups who will either smoke or not smoke regardless of whether or not they try vaping. Without getting our hands dirty and making a serious attempt to disentangle this mess of different response types, we don’t have a hope of working out how many gateway cases there really are.


This means that most studies on the gateway effect are nonsense, because these things are really tough to identify and fairly control for using mathematical models. Unfortunately for supporters of vaping, this also means that our claims that “there is no gateway because smoking rates are declining” are basically unsupported too. There could easily be a gateway effect being masked by positive effects, like the protective types and the smokers who switch to vaping. The only good news from declining smoking rates is that we can be pretty sure that the net effect of vaping on the population is good.


If you’re now wondering whether there’s any hope at all, you’re pretty much on the right track. How can we ever hope to control for all of these things that could affect what we find? How could we ever find out if there’s a gateway effect?


I asked Carl:


Carl V. Phillips - Anti THR LiesAs I lay out my previous paper, the best chance of measuring the effects lies in either natural experiments or really good propensity scores.


An example of a natural experiment would be to take advantage of vaping being a fad among teenagers that has (or at least had) very uneven uptake. If someone were to identify high schools with high vaping rates and match them to demographically very similar schools with low rates, and then compare smoking rates, we could estimate the net effect (causal cases minus protective cases). That would not exactly measure the gateway effect because of that problem I just explained. But it would offer a measure of the net of causal minus protective types in the exposed population and this net seems to be what most political debates focus on (though a deeper dive into the moral philosophy suggests that saying protective and causal cases just cancel each other out is not an easily defensible position).


A propensity-score based approach would be to create the best available estimator of whether someone is destined to smoke (asking lots of questions about preferences, behaviors, and exposures) that is independent of vaping exposure, and then see if vaping exposure is associated with smoking among many who otherwise appear destined to not smoke. Since no propensity score is perfect, this would probably require some fairly sophisticated statistics as well as a serious stepwise approach.


I realize that is fairly opaque. Which is the real point: Using propensity measures or tracking natural experiments would require a lot more work than the standard practice of throwing together a half-assed survey about behaviors and a few demographic questions, and administering it to a convenient population. It would require skills that few who study tobacco use have. It would also require serious scientific honesty, because it is trivially easy to pretend to be seeking the truth using methods like that, but really just be dressing up a politically determined conclusion.

– Carl V. Phillips (Anti-THR Lies


The short version is that finding gateway effects is hard work, and the truth seems to be that there is little motivation to really do it. And this is where we need to leave the science and look at the politics of gateway claims, because ultimately, they’re more political than scientific anyway.


There is No Good Evidence For a Gateway Effect, But We Can’t (Completely) Refute it Either


To conclude the first part of this post, the cold hard truth is that gateway effects could exist. The problem, though, is that we don’t have the evidence we need to answer the question, because all the studies we have are weak to the point of being difficult to interpret.


Based on the very low number of never-smoking teens who regularly vape, the low number of vaping teens who actually consume nicotine, the still-declining smoking rate, the lack of plausibility of a gateway from vaping to smoking and the lack of good evidence to support it, we can make a very strong argument that the vaping-to-smoking gateway effect is unlikely to be a significant problem. But, as much as we might like to, we’re not in the position to completely discount the possibility either.


This is because when we’re talking about the science, our ideological or political opposition to gateway claims doesn’t matter; it matters what we can prove.


We’d like to thank Michael Siegel and Carl V. Phillips for their insightful comments, and for making this post possible!


Lee Johnson is a writer and vaper from the UK. He started vaping in 2012, and since then has contributed to E-Cigarette Reviewed, E-Cigarette Direct’s Ashtray Blog and Vaping360. He strongly believes smokers need accurate information about vaping and other reduced-harm alternatives to smoking. He has a degree in physics from the Open University and a passion for all forms of science.

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