Vaping among young people is associated with higher subsequent consumption of tobacco, marijuana or alcohol

The article presents solid and rigorous work, befitting publication in a high-impact journal such as Tobacco Control. Its umbrella review format, including 56 systematic reviews and meta-analyses, gives it great methodological strength in synthesising a large body of evidence. Although it is acknowledged that many of the primary studies are observational and that many of the reviews included are of low quality according to AMSTAR-2, the consistency of the findings and the relevance of the topic to global public health reinforce the validity and relevance of the work. Overall, this is a high-quality scientific article with a direct impact on the current debate on youth vaping regulation.

The study confirms and expands the existing evidence on the risks of vaping in young people. Although partial reviews had already been published, this is the first umbrella review focused exclusively on young people and a wide range of outcomes (physical and mental), representing a novel and necessary contribution. The findings are consistent with previous theories such as the ‘gateway’ effect to smoking and other substances, and add relevant data on mental health (risk of depression, suicidal ideation and behaviour), fertility, oral health and injuries.

In terms of implications, the results strongly support the need to strengthen regulatory policies: limiting the sale and advertising of e-cigarettes to minors, controlling designs that are attractive to adolescents, and increasing prevention and counter-marketing campaigns against industry strategies. The fact that the findings are published in a leading journal gives them even more weight for consideration in the formulation of international public health policies.

[Regarding possible limitations], the article itself acknowledges several:

• The methodological quality of the included reviews is mostly low or critically low, which limits the robustness of the conclusions.
• The predominance of observational studies makes it difficult to establish definitive causality, although the consistency of the associations suggests a probable link.
• There is heterogeneity in populations, exposure measures and outcomes, which may influence the reported effect sizes.
• Some areas (such as cardiovascular effects, addiction, neurodevelopment or fertility) still have little evidence and require further longitudinal research.

Even so, these limitations do not invalidate the central message: vaping among young people is clearly associated with multiple risks, and health authorities must act accordingly.

Although the use of electronic cigarettes is a much more recent behaviour than tobacco consumption, numerous studies have been conducted to assess the health impact of using these devices. Systematic reviews have also been published which, by analysing the results of different individual studies together, provide more robust scientific evidence.

The study just published in Tobacco Control follows the “umbrella review” approach to obtain a synthesis of 56 systematic reviews of the impact of electronic cigarette use on health among young people under 25, which in turn were based on 384 different scientific articles. The results presented by the authors show an association between the use of electronic cigarettes and the development or exacerbation of various health problems such as bronchial asthma and other respiratory conditions, burns and other unintentional injuries, and, most notably, the initiation of tobacco use and other addictive products such as cannabis derivatives and alcoholic beverages. Of particular note is the fact that 21 systematic reviews have shown that young people who use electronic cigarettes are three times more likely to subsequently start smoking tobacco than those who do not use these devices.

Public health policies on tobacco control have among their main objectives the prevention of smoking initiation during adolescence and youth. As e-cigarette use is known to be very common among young people and adolescents, it is very important to understand how it affects their tobacco use and to act accordingly. The available scientific evidence, such as that gathered in this new study, shows that the spread of e-cigarette use among young people and adolescents can lead to an increase in subsequent tobacco use, as well as contributing to various diseases. It is necessary to implement activities to prevent the use of electronic cigarettes among young people, such as the development of communication campaigns based on evidence provided by behavioural sciences, as well as the control of the marketing of devices designed specifically to attract younger consumers, such as disposable electronic cigarettes or those that incorporate certain flavours and designs.

This research is a compilation of observational studies, each of which compares vaping users against non-users. As such, it can say that vaping users are more likely to engage in certain behaviours, but whether vaping is truly a cause of these behaviours is beyond the scope of the data. However, the associations demonstrated are both extensive in scope and strong in magnitude – it is clear that vaping users are at higher risk of many diseases than non-users. A causal explanation to the findings is both plausible and consistent with the evidence provided but such a finding can only be made conclusively by a randomized trial. Given that a large-scale long-term trial would be impractical and potentially unethical, it is likely that we will never have conclusive evidence demonstrating that vaping behaviour is a cause of health outcomes. Vaping users need to make decisions about their behaviour based on evidence that is inherently uncertain, but links vaping usage with a host of negative outcomes.

This umbrella review brings together in one place issues relating to young people, e-cigarettes and health effects. It reported on 56 systematic reviews of which 53 were rated critically low or low quality, meaning authors should be extremely cautious before making any conclusions.

The authors reported that the reviews found consistently that vaping was associated with subsequent smoking. This replicates the findings of many previous reviews and indeed research I have been involved in. However, the authors incorrectly state that this supports ‘a causal relationship’ in other words that vaping causes smoking (the so-called ‘gateway’ effect). It is well-established that consistency does not mean causality. In this case, individual-level studies that were the focus of these reviews do not take into account all the possible influences on these behaviours, such as being sensation-seeking or impulsive which might make young people more likely to vape and to smoke. Our research also showed the opposite relationship - that trying a tobacco cigarette was associated with subsequent vaping. Indeed, a recent well conducted systematic review published using gold standard methods, reported a similar finding to the umbrella review for individual-level studies - but it found the opposite in studies examining population-level trends in vaping and smoking, so as youth vaping increased in a population, smoking reduced. Given these authors also talked about limited evidence, we need more and better research to be able to make confident conclusions about the relationship between youth e-cigarette use and health outcomes.

The umbrella review’s finding of a relationship between vaping and subsequent substance use suffers from similar issues. Furthermore, findings on other health outcomes were often examined in cross-sectional studies, which take a snapshot of people at one point in time. These simply show a relationship, such as that between vaping and mental health but cannot say anything about what came first, and hence whether vaping caused the mental health condition or whether the mental health condition caused young people to vape.

Nevertheless, we are all keen to protect young people’s health and concerns about youth smoking and vaping have prompted the government to introduce its Tobacco & Vapes Bill and its passage through Parliament should be accelerated.