The study's lead author, Stanton Glantz, a professor of medicine at the University of California, San Francisco, who has been critical of the devices, said the results suggested that e-cigarettes, whose use is growing rapidly among youth and adults, were leading to less quitting, not more.
"The use of e-cigarettes does not discourage, and may encourage, conventional cigarette use among U.S. adolescents," the study concluded. It was published online in JAMA Pediatrics on Thursday.
But other experts said the data did not support that interpretation. . They said that just because e-cigarettes are being used by youths who smoke more and have a harder time quitting does not mean that the devices themselves are the cause of those problems. It is just as possible, they said, that youths who use the devices were heavier smokers to begin with or would have become heavy smokers.
"The data in this study do not allow many of the broad conclusions that it draws," said Thomas J. Glynn, a researcher at the American Cancer Society.
The study is likely to further stir the debate over what electronic cigarettes mean for the nation's 45 million smokers, three million of whom are adolescents. Some experts worry that e-cigarettes is a gateway to smoking real cigarettes for young people, though most say the data is too skimpy to settle the issue. Others hope the devices could be a path to quitting.
So far, the overwhelming majority of young people who use e-cigarettes also smoke real cigarettes, a large federal survey published last year found.
Still, while e-cigarette use among youth doubled from 2011 to 2012, cigarette smoking for youth has continued to decline. The smoking rate hit a record low in 2013 of 9.6 percent, down by two-thirds from its peak in 1997.
The new study drew on broad federal survey data from more than 17,000 middle school and high school students in 2011 and more than 22,000 in 2012. But instead of following the same students over time – which many experts say is crucial to determine whether there has been a progression from e-cigarettes to actual smoking — the study examined two different groups of students, essentially creating two snapshots.
Image: Teen smoking e-cigarette, via Shutterstock