E-cigarettes are expanding tobacco product use among youth:
In the first national analysis of the impact of e-cigarettes on trends in youth smoking in the United States, UCSF researchers did not find evidence that e-cigarettes have caused youth smoking to decline. In fact, combined e-cigarette and cigarette use among adolescents in 2014 was higher than total cigarette use in 2009, according to the study.

Read more at: https://medicalxpress.com/news/2017-01-e-cigarettes-tobacco-product-youth.html#jCp