E-cigarettes are electronic devices designed to deliver nicotine with flavorings. They are marketed as an aide for stopping smoking. However, a new study has revealed that it may instead nudge teens towards tobacco. Teenagers who used an e-cigarette were more likely to take up smoking a year later than those who never did, said the paper.
Researchers in the United States interviewed more than 2,300 Hawaiian school children, their average age just under 15 years, in 2013, and asked them if they had ever smoked or 'vaped' - inhaling and blowing out the vapor generated by an e-cigarette.
A year later, about half the group was questioned again.
"Adolescents who use e-cigarettes are more likely to start smoking cigarettes. This result together with other findings suggests that policies restructuring adolescents' access to e-cigarettes may have a rationale from a public health standpoint," concluded the authors of the study published in Tobacco Control.
But experts not involved in the study said the evidence was flimsy, and did not prove that e-cigarettes cause smoking.
"Does one lead to the other? Or does using e-cigs define a certain population of teens, i.e. the ones most likely to start smoking anyway?" said a commentary compiled by the Science Media Center.
According to the study, just under 31% of the teens sampled had used an e-cigarette at least once in 2013, while about 15% had smoked at least one cigarette.
The US Centers for Disease Control and Prevention estimates that from 2011 to 2014, e-cigarette use among high school students grew from 1.5-13.4%.
Health experts and watchdogs are embroiled in debate as to whether e-cigarettes, often not strictly regulated, are safe, or even useful as a smoking cessation aid.
Earlier this month, another US-based study said that e-cigarettes lowered the odds of successfully quitting - but that research too was criticized as flawed.