(Reuters Health) - Adolescents and young adults who try e-cigarettes are more than three times as likely to take up smoking traditional cigarettes as their peers who haven't tried the devices, a research review suggests.

E-cigarette use, or vaping, was as least as strong a risk factor for smoking traditional cigarettes as having a parent or sibling who smokes or having a risk-taking and thrill-seeking personality, researchers found.

"E-cigarette use among teens and young adults could increase the future burden of tobacco by creating a new generation of adult smokers who might have otherwise not begun smoking," said lead study author Samir Soneji of the Dartmouth Institute for Health Policy and Clinical Practice in New Hampshire.

Big tobacco companies, including Altria Group Inc, Lorillard Tobacco Co and Reynolds American Inc, are all developing e-cigarettes. The battery-powered devices feature a glowing tip and a heating element that turns liquid nicotine and other flavorings into a cloud of vapor that users inhale.

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Soneji and colleagues analyzed data from nine smaller studies with a total of 17,389 participants ages 14 to 30.

They didn't examine why many teens and young adults transitioned from vaping to smoking traditional cigarettes, but both options contain nicotine, an addictive drug, Soneji said by email.

The habit of vaping may also make the transition to smoking seem more natural, and teens in particular may gravitate toward friends who smoke once they try vaping, Soneji said.

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"To the extent that e-cigarette use mimics the behavior of smoking a cigarette - handling the e-cigarette, the action of puffing, and the inhalation of smoke - it sets the adolescent up for easily transitioning to smoking," Soneji said. "Like transitioning from driving a Tesla to driving a Chevy."

Seven studies looked at smoking initiation among more than 8,000 youngsters who had never smoked before. Data pooled from these studies showed that roughly 30 percent of e-cigarette users became smokers, compared with only about 8 percent of people who hadn't tried vaping. That translates into 3.6 times higher odds of smoking for people who have tried e-cigarettes, researchers report in JAMA Pediatrics.

One limitation of the study is that it included some results from earlier studies with a high drop-out rate, and it's not clear whether people who left these studies were different from participants who remained in ways that would make them more or less likely to smoke, the authors note. Researchers also lacked data on the type of e-cigarettes used, and they only looked at U.S. studies.

Even so, by pooling data from several smaller studies, the results offer stronger evidence that vaping can encourage young people to progress to smoking, said William Shadel, a researcher at RAND Corporation in Pittsburgh who wasn't involved in the current study.

"The results are particularly compelling because the studies took into account other variables that put kids at risk of cigarette smoking, like alcohol use and peer cigarette smoking," Shadel said by email. "These results should help to strengthen arguments for regulatory action that limits young people's access to e-cigarettes."

Enticing flavors of liquid nicotine used in e-cigarettes, like strawberry or chocolate, may make vaping appealing to some young people who might not like the taste of traditional cigarettes, said Dr. Brian Primack, a researcher at the University of Pittsburgh who wasn't involved in the study. Peer pressure may then encourage them to graduate to smoking.

"Young people report that there is a lot of pressure among e-cigarette only users to smoke a 'real' cigarette," Primack said by email. "It may be somewhat analogous to the fact that teens who use flavored alcohol are often pressured socially to step up their game to harder forms of alcohol."

There's one clear way for young people to avoid this.

"The biggest thing that people can do is never start using them in the first place," Primack said.

SOURCE: bit.ly/2tbQ8JY JAMA Pediatrics, online June 26, 2017.