The Journal of the American Medical Association has published a paper  looking at what happens to 14 year old adolescents from Los Angeles County schools who had never smoked tobacco products, but had used an e-cigarette at least once. Unsurprisingly, some of these teenagers go on to smoke. Unsurprisingly, some commentators will claim this study shows a gateway effect. Before a new moral panic takes hold, there are three main points to draw out:
(1) they were observing teenage experimentation. The observations are actually of “ever use” (taking one puff or more) both for e-cigarettes and with smoking, rather than regular or daily use. What the study is actually observing is teenage experimentation or messing about, not consolidated addictive behaviour. We don’t even know if those who started vaping then tried smoking carried on smoking, returned to vaping or did neither. The most that can be said of ever-users is that they show a willingness to experiment – and this is all the researchers have discovered… that some kids experiment with smoking and vaping – and other risky behaviours – because that’s the sort of teens they are.
(2) they did not and could not find a gateway effect. It is not possible to conclude that smoking is caused by prior e-cigarette use from this data (and the authors are clear about that) so no-one should be stating that this establishes a gateway or even hints at it. Rather than e-cigarette use causing smoking, both e-cigarette use and smoking may be caused by other independent risk factors – adolescent characteristics that incline them to both smoking and vaping (or, more precisely to experimenting with smoking and vaping). Although they tried to adjust for this, it is hard to see how it could be done convincingly for this population and these behaviours.
(3) they have not recognised that e-cigarettes might be displacing smoking in three ways. They have not reported on what happened to those who started smoking first and then took up e-cigarettes. They have not shown whether those who started on e-cigarettes but did not go on to smoke may have tried smoking in the absence of e-cigarettes (i.e. smoking initiation was avoided). They have not shown the availability of e-cigarettes might cause those who started smoking to stop subsequently by switching back to e-cigarettes or using them to quit.
Given the way the study is described in the media release it is bound to be wilfully misunderstood (predictably see Tobacco Free Kids hyping it up) and will probably contribute to greater global misunderstanding of this issue. So I am providing a commentary for journalists and other interested parties by commenting on the media briefing sent out from JAMA – my comments are marked ‘comment’ and coloured blue – the rest is from the media advisory. I have provided links to the actual articles and two associated commentaries that were referenced in the media advisory.
Update 25 September. An excellent critique by Prof Lynn Kozlowski: Vaping as a ‘gateway’ to smoking is still more hype than hazard
Media Briefing: Teens Who Use E-Cigarettes May Be More Likely to Begin Smoking
Comment on the title: adolescents who use e-cigarettes may be more likely to begin smoking, but not necessarily because they used e-cigarettes. The most likely explanation is that whatever it is that inclines young people to smoke (actually to experiment), also inclines them to use e-cigarettes. It could be one or more independent factors such as smoking parents, peer group bonding, poor educational attainment, mental illness, rebellious nature etc that make an adolescent more likely to both try smoking and vaping. This idea is sometime known as ‘shared liability’ or common risk-factors. The authors have tried to adjust for these factors, but it difficult to choose the right risk factors and give them due weighting – and to ensure they apply to the actual population under observation. However, the newsworthy findings of the paper depend entirely on showing that it is something other than these common risk factors that is leading teenagers from vaping to smoking.
Among high school students in Los Angeles, those who had ever used electronic cigarettes were more likely to report initiation of smokable (“combustible”) tobacco (such as cigarettes, cigars, and hookah) use over the next year compared with nonusers, according to a study in the August 18 issue of JAMA.
Comment: this is is not surprising – as above these behaviours have common risk-factors. There is nothing here that suggests the use of e-cigarettes caused the smoking (the authors do acknowledge this in passing). To the extent that e-cigarettes remain in use or displace tobacco consumption this is a good thing because it is reducing smoking. Experience with e-cigarettes may also mean that they switch to vaping at a later stage, if they start to be concerned about their smoking and health. Again, that is a good thing.
The authors are using an especially weak indicator of e-cigarette use: that is “ever use”, which can mean ‘tried one puff once’. ‘Ever use’ is a more appropriate marker for a teenager’s ‘willingness to experiment‘ as a personal characteristic than as a way of characterising a nicotine-using behaviour. Teenage willingness to experiment is the key to understanding these findings.
Combustible tobacco, which has well-known health consequences, has long been the most common nicotine-delivering product used. Electronic cigarettes (e-cigarettes), which are devices that deliver inhaled aerosol usually containing nicotine, are becoming increasingly popular, particularly among adolescents, including teens who have never used combustible tobacco. According to 2014 U.S. estimates, 16 percent of 10th graders reported use of e-cigarettes within the past 30 days, of whom 43 percent reported never having tried combustible cigarettes. Whether use of e-cigarettes is associated with risk of initiating combustible tobacco use has not been known, according to background information in the article.
Comment: it is at all not surprising to find an association between e-cigarette use and smoking. But even among teens who never used tobacco, e-cigarette use may be beneficial rather than harmful. It depends what they would have done in the absence of e-cigarettes. If they would have become smokers (likely because of the shared liability idea) then their e-cigarette use might be a diversion from smoking or reducing it and therefore beneficial.
An especially striking feature of the data is that almost half (49%) of those who had ever used e-cigarettes but had never smoked declared ‘substance use’ (see table 1) – again suggesting that the authors are observing nothing much more than teenage experimentation but placing too much weight on the order in which it happens (a way of implying that one leads to another). The study says very little about this, but substance use is just another risky behaviour.
Adam M. Leventhal, Ph.D., of the Keck School of Medicine of the University of Southern California, Los Angeles, and colleagues examined whether adolescents who reported ever using e-cigarettes were more likely to initiate the use of combustible tobacco (cigarettes, cigars, and hookah) during the subsequent year. The study included 2,530 students from ten public high schools in Los Angeles who reported never using combustible tobacco at study entry (fall 2013, 9th grade, average age = 14 years) and completed follow-up assessments at 6 months (spring 2014, 9th grade) or 12 months (fall 2014, 10th grade). At each time point, students completed self-report surveys on any use of combustible tobacco products.
The researchers found that e-cigarette users (n = 222) were more likely than never users (n = 2,308) to report past 6-month use of any combustible tobacco product at the 6-month follow-up (31 percent vs 8 percent) and at the 12-month follow-up (25 percent vs 9 percent). Baseline e-cigarette use was associated with a greater likelihood of use of any combustible tobacco product averaged across the 2 follow-up periods in the analyses adjusted for sociodemographic, environmental, and intrapersonal risk factors for smoking. In addition, relative to baseline e-cigarette never users, e-cigarette ever users were more likely to be using at least 1 more combustible tobacco product averaged across the 2 follow-up assessments.
Comment: the most reasonable interpretation of the results is that they are observing teenage experimentation – of cigarettes, drugs, e-cigarettes. If they have characteristics that lead them to experiment, then they are likely to experiment with many things. Note this is quite an unusual subset of the American population – only 16% identified as white, nearly half were Hispanic. Of the 222 students who had used e-cigarettes but not smoked, about half (109) declared substance use. They are attempting to correct for risk factors for smoking, but what they are actually have is observations of experimentation – who is to say the risk factors are the same? Being a smoker/vaper and trying a cigarette/e-cigarette are quite different behaviours. Or, to put it more bluntly, they found “people who try stuff, try stuff”:
@Clive_Bates Impulsivity data suggests whole thing boils down to: People who try stuff, try stuff…
— Marcus Munafo (@MarcusMunafo) August 20, 2015
“These data provide new evidence that e-cigarette use is prospectively associated with increased risk of combustible tobacco use initiation during early adolescence. Associations were consistent across unadjusted and adjusted models, multiple tobacco product outcomes, and various sensitivity analyses,” the authors write.
Comment: the use of ‘associated’ here means ‘can be observed’ or ‘correlated’. It does not mean ’caused by’.
They add that “some teens may be more likely to use e-cigarettes prior to combustible tobacco because of beliefs that e-cigarettes are not harmful or addictive, youth-targeted marketing, availability of e-cigarettes in flavors attractive to youths, and ease of accessing e-cigarettes due to either an absence or inconsistent enforcement of restrictions against sales to minors.”
Comment. This is pure speculation – there is nothing in the research that shows a causal link between e-cigarette use and smoking, let alone any way of identifying specific factors within e-cigarette use to which a causal link can be attributed. There is no evidence that particular flavours attract young people or any more than adults. Young people are right to believe that e-cigarettes are much less harmful and addictive than cigarettes (it is unclear what the authors think). There isn’t any good evidence that marketing targets youth rather than adult smokers. This paragraph has the beneficial effect of revealing investigator bias.
The reference to ‘prior’ use betrays a confusion about causal pathways. Real gateway effects have little to do with the order in which behaviours start: did the thing they started doing first lead to the thing that they started doing next? In fact the order is not important – what matters is if one behaviour (vaping) causes another more harmful behaviour (smoking) to consolidate into an addictive habit which would not have happened in the absence of the less harmful behaviour. In theory a teen could start smoking first but only continue to smoke because they subsequently took up vaping as well: there is no evidence that this happens, but I raise it to make the point that in causation the starting order doesn’t matter.
“Further research is needed to understand whether this association may be causal.”
Comment. In other words, “We would like to make it clear that nothing in this research shows that prior e-cigarette use causes adolescent smoking“. They include this rather important qualification almost as an afterthought in the media briefing, though it is stated more clearly in the article. It is worth bearing in mind that US teenage smoking rates have been falling at an accelerated rate over the period that adolescent e-cigarette use has been rising. The authors should have discussed this population level phenomenon because it is important context that provides a ‘reality check’ on the implied story in this research.
 Leventhal AM, Strong DR, Kirkpatrick MG, Unger JB, Sussman S, Riggs NR, et al. Association of Electronic Cigarette Use With Initiation of Combustible Tobacco Product Smoking in Early Adolescence. JAMA [Internet]. American Medical Association; 2015 Aug 18;314(7):700.
Editorial: E-Cigarette Use and Subsequent Tobacco Use by Adolescents
The report by Leventhal and colleagues is the strongest evidence to date that e-cigarettes might pose a health hazard by encouraging adolescents to start smoking conventional tobacco products, writes Nancy A. Rigotti, M.D., of Massachusetts General Hospital and Harvard Medical School, Boston.
Comment. Note how the confidence firms up between the reporting of the research and introduction to the commentary: “strongest evidence to date that e-cigarettes might pose a health hazard by encouraging adolescents to start smoking“. The phrase ‘pose a health hazard’ implies a causal link – but they have not found a causal link.
Regardless of whether e-cigarettes are a gateway to tobacco product initiation, there is no reason for adolescents to use a product for which the hypothesized public health benefit is harm reduction for adult smokers. However, there is ample evidence that e-cigarettes are marketed in ways that appeal to children and adolescents. Prompt, effective action is needed to protect youth and reduce the demand for e-cigarettes by nonsmokers of all ages. A rational approach is to extend to e-cigarettes the same sales, marketing, and use restrictions that apply to combustible cigarettes.”
Comment. The author writes as though adolescents are making rational long-term choices, rather than understanding their behaviour or the causes of smoking – of course there is no need to vape or smoke, and most adolescents don’t. However, some do undertake risky behaviour – smoking, drugs, fighting, unprotected sex, binge-drinking, driving while intoxicated etc. Given that reality, there is a good reason for some teenagers to use e-cigarettes if it means they otherwise would have smoked. There is no reason why ‘harm reduction’ should start at 18 or why young addicted smokers should not turn to e-cigarettes. There is nothing in this research that justifies the author’s policy prescription – to treat e-cigarettes like cigarettes – nor is it somehow ‘rational’ not least because e-cigarettes are at least 95% lower risk than smoking. The author just ignores the obvious unintended consequence of clamping down hard on e-cigarettes – that it protects the cigarette trade from competition from much lower risk products. The authors have provided no impact assessment and not one jot of evidence argument – scientific, economic, commercial, ethical, legal – to support this idea. It reflects a tendency of some scientists (and journals) to greatly exceed their area of competence. How do they know this proposal won’t be worse for health than doing nothing at all?
Related Viewpoint: The Global Health Implications of e-Cigarettes
In an accompanying Viewpoint, Andrew Y. Chang, M.D., and Michele Barry, M.D., of the Stanford University School of Medicine, Stanford, Calif., discuss health considerations of e-cigarettes unique to low- and middle-income countries.
“Developing nations should not underestimate the availability and targeted marketing of electronic nicotine delivery systems (ENDS) within their borders and should place e-cigarettes under the purview of their medical and pharmaceutical regulatory boards. Low- and middle-income countries can feel empowered to exclude multinational tobacco companies from this regulatory process in accordance with Article 5.3 of WHO’s Framework Convention on Tobacco Control, which warns against the conflict of interest posed by the industry in this sphere.”
Comment. This commentary goes far beyond any conclusions that can be drawn from the related research. The effect of applying medical regulation has been to create a de facto prohibition everywhere it has been done. The only products likely to be legally available under such a regime would be commoditised simple devices made by tobacco companies. It is hard to see why these American-based academics think that consumer choice for nicotine users in developing countries should be restricted to only the most dangerous products – cigarettes. They have not provided any evidence of wrong-doing by tobacco companies with respect to e-cigarette business practices, but seem to be suggesting that is an important issue. Most neutral observers would regard the tobacco companies switching their product lines and customers to lower risk products as a welcome development, and (like me) push them to move faster in this direction.
“International nongovernmental organizations such as the Gates Foundation and the Bloomberg Initiative to Reduce Tobacco Use should support these efforts to provide consistency in control and enforcement of ENDS legislation. Even though e-cigarettes may have a future as smoking cessation tools, evidence to support this indication is lacking. More rigorous studies must be conducted regarding the awareness, usage patterns, and potential for harm of these devices in low-income countries, particularly Africa and South Asia, where data are currently missing.”
Comment: better advice would be to promote enforceable light touch regulation that allows e-cigarette use to displace smoking. The ‘death by red tape’ e-cigarette regulatory ideas of these academics amount to a protection of the cigarette trade and are more likely to add to the death toll than to reduce it.
Other comments on these papers
- Mike Siegel (The rest of the story): According to Campaign for Tobacco-Free Kids, New Study Suggests E-Cigs are a Gateway to Smoking
- Konstantinos Farsalinos (E-cigarette Research): A new study finding e-cigarettes are gateway to smoking? Not really
- Linda Bauld (Cancer Research UK): Young people and e-cigarettes what we know so far
- Bill Godshall (Smokefree Pennsylvania) has pulled it all together: FDA/NIH funded junk e-cig gateway study touted by JAMA intended to promote FDA e-cig ban