While adolescents using e-cigarettes were more likely to be trying to quit, they were less likely to have stopped smoking and were smoking more, not less, the research found.
"We are witnessing the beginning of a new phase of the nicotine epidemic and a new route to nicotine addiction for kids," according to senior author Stanton A Glantz, from the University of California, San Francisco (UCSF).
E-cigarettes are battery-powered devices that look like cigarettes and deliver an aerosol of nicotine and other chemicals.
The devices are largely unregulated, with no effective controls on marketing them to minors, they said.
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In the study, researchers assessed e-cigarette use among youth in Korea, analysing smoking among some 75,000 Korean youth.
"Our paper raises serious concern about the effects of the Wild West marketing of e-cigarettes on youth," said Glantz.
The researchers reported that four out of five Korean adolescent e-cigarette users are "dual" smokers who use both tobacco and e-cigarettes.
"Use of e-cigarettes is associated with heavier use of conventional cigarettes, which raises the likelihood that actual use of e-cigarettes may increase harm by creating a new pathway for youth to become addicted to nicotine and by reducing the odds that an adolescent will stop smoking conventional cigarettes," researchers said.
Among students who used e-cigarettes, 8 per cent were concurrently smoking conventional cigarettes. After adjusting for demographics, current cigarette smokers in the study were found to be much more likely to use e-cigarettes than non-smokers.
Students no longer using cigarettes were rare among current e-cigarette users, the researchers said.
The study appears in the Journal of Adolescent Health.