A team of public health researchers found "very low-certainty evidence" to support a commonly held belief that nicotine vaping is a gateway to cigarette smoking for young people.
"One of the substantial concerns from some members of the public health community about vaping is that it might cause more young people to smoke," says Jamie Hartmann-Boyce , assistant professor of health policy and management at the University of Massachusetts Amherst and senior author of a new review paper published in the journal Addiction . "Some – but not all – evidence from our study possibly suggests the opposite – that vaping may contribute to declines in youth smoking, particularly in the US."
But it's a very tricky, contentious issue, and the findings from the 123 studies that the team reviewed – with some 4 million participants under age 29 in the US, Canada and Western Europe – can be interpreted in a variety of ways.
The researchers, including lead authors Monserrat Conde and Rachna Begh of the University of Oxford in the United Kingdom, stress that the only clear finding from their research is that there is no clear finding. "We need more studies to establish any causal links," Conde says.
"The studies themselves are not straightforward study designs, because you can't randomize kids to vape or not vape – it just wouldn't be ethical," Hartmann-Boyce says. "But it means that that there are so many different ways to interpret the findings of these studies."
For example, data from 21 of the larger studies were mixed, but on balance suggested that as rates of vaping went up among young people, smoking rates went down. And when vaping was restricted, smoking rates went up. However, not all studies showed this, and some found the opposite effect, the authors note.
At the individual level, the study clearly found that young people who vape appear to be more likely to go on to smoke than people who do not vape, but it was unclear whether one caused the other – in other words, whether these young people went on to smoke because they had vaped. It's possible some of the youth who vape would otherwise have become smokers if they didn't vape, Hartmann-Boyce adds.
"There's enough non-smoking kids who start vaping in the US that if vaping was in a consistent and widespread way causing kids to start smoking, we would start seeing that in our population-level smoking data," Hartmann-Boyce says. "And we haven't seen that at all."
In fact, smoking rates among youth have been steadily declining for years, according to statistics from the U.S. Centers from Disease Control and Prevention (CDC). The number of high school students who reported smoking cigarettes in the past 30 days has dropped from 15.8% in 2011 to 4.6% in 2020 to 1.7% in 2024.
"The smoking rates among kids have declined steeply, and whether or not that's due to vaping or something else is up in the air," Hartmann-Boyce says. "But it's difficult to argue that - in the US population - youth vaping is en masse causing kids to smoke. The data doesn't support that so far."
The researchers looked at this complicated issue because it has implications for public health policy. Previous research from Hartmann-Boyce and team shows that nicotine e-cigarettes can help adults stop smoking. But if research showed that vaping causes youth to start smoking, that would be a "powerful reason" to restrict e-cigarettes.
