The observed gateway effect of e-cigarette use among teens is “likely to be small,” with only a tiny proportion of experimental vapers going on to smoke regular cigarettes, suggests a piece of research published online in the journal Tobacco Control.

If anything, young vapers are less likely to go on to smoke regular cigarettes than their peers who try other tobacco products first, the findings indicate.

The potential gateway impact of e-cigarettes in teen smoking uptake has been hotly contested. Several studies have linked teen vaping to a heightened risk of smoking.

However, the research indicates that most of these studies have looked only at initial uptake, and not continued use. And for obvious reasons, no clinical trials can actually test whether e-cigarette use inevitably leads to smoking.

To try and produce a more nuanced analysis of the issues, the researchers compared first experimentation with different types of tobacco products among 40,000 US teens, using responses to the National Youth Tobacco Survey from 2014 to 2017.

The teens were asked if they had ever tried a cigarette, even if it was only a puff or two. Those who said yes, were classified as ever smokers; those who had smoked at least one cigarette in the past 30 days were also classified as ever smokers; while those who had smoked more than 100 cigarettes to date were classified as established smokers.

Teens in each of these groups who had tried e-cigarettes first were compared with those who had first used other combustible tobacco products, such as cigars, cigarillos, hookahs, or pipes, and those who had first used non-combustible tobacco products, such as snuff and chewing tobacco.

The three groups of smokers who had first tried e-cigarettes were then matched with teens with similar social, demographic, and behavioural characteristics, including vulnerability to taking up smoking, but who hadn’t tried e-cigarettes first.

This was done using a statistical technique called PSM, which simulates clinical trials and reduces the influence of other potentially important factors.

The most common ‘starter’ product was cigarettes, the findings showed, followed by other combustibles, e-cigarettes, and non-combustibles. This is despite e-cigarettes being more frequently used than any other product from 2015 onwards.

Girls were less likely than boys to have tried any tobacco products, but, overall, the likelihood of experimentation rose with increasing age.

Compared with those who first used tobacco alternatives to cigarettes, those who first tried e-cigarettes were less likely to have ever smoked cigarettes.

Less than 1% of teens who tried e-cigarettes became established smokers, a proportion that was significantly smaller than any other category.

The conversion rate from ever to established smoking was much lower for teens who tried e-cigarettes first: 2.7%, compared to 9% for first time combustible product consumers and almost 16% for first time non-combustible product consumers. These findings were supported by the PSM analysis.

“The association of subsequent use of e-cigarettes was stronger for adolescents initiating with cigarettes than the association of subsequent cigarette smoking for e-cigarette initiators,” wrote the researchers.

“This underlines the fact that cigarettes act as a more prominent gateway for any product use,” they explained.

This is an observational study, and as such, does not establish causality; not all factors that might have potentially influenced the findings, such as behaviour and mental health issues, were accounted for.

Nevertheless, the findings of their analysis lead the researchers to conclude, “Over the time period considered, e-cigarettes were unlikely to have acted as an important gateway towards cigarette smoking, and may, in fact, have acted as a gateway away from smoking for vulnerable adolescents….The postulated gateway effect is likely to be small.”

According to a previous study published by researchers from the University of Pittsburgh, published in the American Journal of Medicine, young adults who use electronic cigarettes are more than four times as likely to begin smoking tobacco cigarettes within 18 months as their peers who do not vape.

The World Health Organization estimates that tobacco kills up to one half of its regular users via cardiovascular disease, lung and other cancers, and respiratory illnesses.

Another study published in Frontiers in Communication said that promotional vaping Instagram posts outnumber anti-vaping content 10,000 to 1.

Despite “The Real Cost” awareness campaign launched by the FDA in 2018, nearly one third of American teenagers are estimated to use e-cigarettes. The current study highlights the limited impact of the FDA campaign, while also using deep learning – an artificial intelligence method – to better understand the marketing tactics used by vaping companies.