- New review finds vaping involved in just 5.3% of teen cigarette experimentation in analysed cohorts
- Most ‘gateway’ studies excluded nearly two thirds of teen vapers and three quarters of new smokers from their main analysis
- Study design prevents detecting any potential ‘diversion’ effect, where vaping may displace cigarette uptake
- They warn that over-regulating vapes on ‘gateway’ grounds “may be detrimental to public health and tobacco control”
A new scientific review is challenging one of the most powerful arguments used to clamp down on vaping: the idea that vapes are acting as a major “gateway” into smoking for teenagers.
Published in the International Journal of Environmental Research and Public Health, the systematic review re-examines 22 longitudinal studies that tracked adolescent “never-smokers” over time to see whether vaping led them to try cigarettes.
These studies – and the meta-analyses built on them – have underpinned many headlines and policy statements claiming that teen vapers are several times more likely to become smokers.
But when the authors reconstructed the full picture, they found that these “gateway” analyses rested on a surprisingly small and highly selected slice of the teenage population.
Only 5% of smoking starts linked to vaping in these cohorts
The review team, led by French pulmonologist Bertrand Dautzenberg, went back to the original cohort data wherever possible. They added back in the adolescents who had been excluded from the “never-smoker” sub-cohorts – including teens who were already smoking, and those who both smoked and vaped at the start of the study.
Once they did that, a very different story emerged. Across 22 cohorts including around 129,800 adolescents, the authors estimate that “e-cigarettes contribute only to 5.3 per cent of T2 cigarette experimentation” – that is, only about one in twenty new teenage cigarette experimenters in these datasets followed the path “never-smoker → vaper → smoker”.
By contrast, in the reconstructed full cohorts:
- 74.0 per cent of teens who were smoking by follow-up had already tried cigarettes before the “gateway” analysis even started
- 20.6 per cent of new cigarette experimenters had never vaped at all
So while the sub-cohort odds ratios looked dramatic – adjusted odds ratios ranged from 1.41 to 8.30 for future smoking among never-smokers who had vaped – they were based on a narrow group that doesn’t represent how most teens actually start smoking.
The problem: who gets left out
The review highlights a key design choice shared across these longitudinal studies: before running the “gateway” analysis, researchers stripped out anyone who had ever tried a cigarette at the start of the study, and often anyone who was both smoking and vaping.
According to the 11 studies that reported the right data, this meant:
- 64.3% of teen vape experimenters at baseline were excluded because they were already “dual users”
- 74.1% of teens who had tried cigarettes by follow-up were excluded from the sub-cohorts used to claim a gateway effect
Those exclusions, the authors argue, introduce “a severe bias”. The results may be valid for that tiny, selected group of never-smokers, but they “cast major doubt on the external validity” of broad claims that vaping is driving youth smoking at the population level.
Gateway or diversion?
The review also pulls in other lines of evidence that are often missing from the gateway debate.
Epidemiological data from countries such as the United States and France show a sharp decline in teenage smoking over the same period that vaping has become widely available and popular with young people. At the same time, the age at which adolescents start smoking cigarettes has risen.
Modelling studies using US and New Zealand data suggest that to explain the observed trends in youth nicotine use, there must be a substantial “diversion effect” – where some teens who might previously have smoked instead vape. In one New Zealand analysis, this diversion effect was judged “the most plausible” explanation for more than half of the observed decline in youth smoking.
Several studies looking at the order in which products are tried also suggest that starting with vaping is linked to less progression into regular smoking than starting with cigarettes. In a large French survey, almost half of 17 to 18-year-olds who had ever tried cigarettes went on to daily smoking, compared with fewer than one in five of those who tried vapes first.
What the authors conclude
The review doesn’t claim that there is no pathway from vaping into smoking. It accepts that, for a small minority of adolescents, vaping may precede and possibly contribute to cigarette experimentation.
But the authors argue that focusing only on those never-smoker sub-cohorts, and then generalising their results to all adolescents, is scientifically unsound. They say the unilateral design of these longitudinal studies “prohibits highlighting any Diversion effect, which is the most likely mechanism accounting for the competition between these two products”.
They conclude that while complete nicotine abstinence remains the ideal, “over-regulation of e-cigarettes because of misinterpretation of longitudinal study results may be detrimental to public health and tobacco control.”
