The study found that students who have used electronic cigarettes (e-cigarettes) by the time they start ninth grade are more likely than others to start smoking traditional cigarettes and other combustible tobacco products within the next year.
Electronic cigarettes deliver nicotine to the lungs by heating a liquid solution that contains nicotine and other chemicals to produce an aerosol that the user inhales, a process often called "vaping."
The study compared tobacco use initiation among 222 students who had used e-cigarettes, but not combustible tobacco products, and 2,308 who had neither used e-cigarettes or combustible tobacco products when initially surveyed at the start of ninth grade.
Over the following six months leading into the start of 10th grade, 25.2 per cent of e-cigarette users had used combustible tobacco products, compared to just 9.3 per cent of nonusers.
"While teen tobacco use has fallen in recent years, this study confirms that we should continue to vigilantly watch teen smoking patterns," said National Institute on Drug Abuse (NIDA) Director Nora D Volkow.
Data were collected as part of a longitudinal survey of substance use and mental health among high school students in Los Angeles. The study surveyed students from 10 public high schools selected because of their diverse demographic characteristics and proximity.
The analysis focused on 2,530 students who initially reported never using combustible tobacco and underwent follow-up assessments after six and 12 months.
Students were asked about lifetime and past six-month use of e-cigarettes, combustible cigarettes, full-size cigars, little cigars/cigarillos, hookah water pipes, and blunts.
"While we cannot conclude that e-cigarette use directly leads to smoking, this research raises concerns that recent increases in youth e-cigarette use could ultimately perpetuate the epidemic of smoking-related illness," Leventhal said.
The study was published in the journal JAMA.
