London, Aug 18 (IANS): Researchers have identified a "robust association" between e-cigarette use among teenagers and the increased probability of smoking a cigarette within a year.

"The findings suggest that among the teenagers who had never smoked, the use of e-cigarettes was a strong predicator that within 12 months they would have tried a conventional cigarette," said lead investigator Mark Conner, Professor at University of Leeds in Britain. 

The research, published in the journal Tobacco Control, surveyed 2,836 adolescents from 20 schools in England. 

Some had tried tobacco but the vast majority were non-smokers. A third had used an e-cigarette.

They were re-surveyed a year later and asked if they had tried a conventional cigarette, and how often.

Among the adolescents who had never smoked but had tried an e-cigarette, 118 out of 343 reported smoking at least one cigarette (34 per cent) over the year. 

Among the group who had not smoked and never used an e-cigarette, the figure was 124 out of 1383 (just under nine per cent).

The survey data revealed that e-cigarette use was a greater risk factor for starting smoking in those with no smoking friends than for those who had a friendship network where most smoked.

"Adolescents who have used e-cigarettes and who initially have no friends who smoke may be at particular risk of starting to smoke cigarettes," study co-author Sarah Grogan from Manchester Metropolitan University said. 

"This is particularly interesting as it runs contrary to the suggestion that adolescents who try e-cigarettes would have been likely to try smoking anyway due to factors such as peer pressure from friends who smoke," Grogan said.