Vaping and later smoking in young people: A systematic review

Vapes (e-cigarettes) are handheld devices that work by heating a liquid that usually contains nicotine and flavourings. E-cigarettes allow users to inhale nicotine in a vapour rather than smoke. Because they do not burn tobacco, e-cigarettes do not expose users to the same levels of chemicals that can cause diseases in people who smoke cigarettes.

Using an e-cigarette is commonly known as 'vaping'. For the purposes of this review, we define smoking as the act of inhaling smoke from burning tobacco, most commonly done via smoking cigarettes.

Since the widespread introduction of vapes over 10 years ago, young people have started using them. Many governments, researchers, and policy makers are worried that e-cigarettes might cause more young people to start smoking than would have otherwise. Smoking causes a lot of death and disease worldwide, so stopping young people smoking is a public health priority. Evidence shows nicotine e-cigarettes can help adults stop smoking. However, if vapes cause more young people to smoke than would have otherwise, this might be a powerful reason for governments to restrict access to e-cigarettes. On the other hand, if vapes cause fewer young people to smoke than would have otherwise, then policies that aim to restrict vapes will have the opposite of their intended effect.

We searched for studies that looked at whether smoking rates in groups of young people changed when vapes became more or less available, or were more or less used by young people. We also searched for studies that tracked individuals over time, to look at whether young people who said they vaped were more likely than young people who did not vape to later start smoking, quit smoking, or smoke more frequently.

We included studies published up to 3 April, 2023.

We found 123 studies, including around 4 million young people (aged 29 and younger) in total. Most studies took place in the USA, Canada, and Western Europe.

Not all of our studies were used in our main analysis. Instead, for our main results we focus on the larger studies.

Data from 21 of the studies looking at groups of young people were mixed, but on balance suggested that as rates of vaping went up among young people, smoking rates went down. When vaping was restricted, smoking rates went up. However, not all studies showed this, and some found the opposite effect.

Twenty-eight studies that tracked individuals over time showed that young people who vaped were more likely to start smoking than young people who did not vape. However, we cannot be sure that vaping was the reason they later started smoking.

Five studies showed that young people who both vaped and smoked were more likely to increase how much they smoked, compared with young people who smoked but did not vape. Again, whether one caused the other was unclear.

Four studies showed mixed findings on whether young people who vaped and smoked were more likely to quit smoking later, compared with young people who only smoked.

Our findings are very uncertain because of issues with the ways the studies were conducted, and some unexplained differences in the results of studies.

Though young people who vape are more likely to go on to smoke than young people who do not vape, it's unclear whether one causes the other. Overall, the introduction of vapes seems to have led to fewer young people smoking than would have otherwise, but this evidence is very uncertain, and future studies are likely to change our findings. We need more well-conducted studies in this area.