E-cigarettes aren't likely to keep kids away from traditional cigarettes, a U.S. study suggests.

Instead, researchers found, adolescents who experimented with e-cigarettes ended up smoking traditional cigarettes just as much as teens who never tried vaping.

"The findings show that e-cigs do nothing to deter the amount of combustible smoking in youth," said lead study author Jessica Barrington-Trimis of the Keck School of Medicine at the University of Southern California in Los Angeles.