A study of some 40,000 US adolescents has found an association between smoking and e-cigarette use but failed to provide evidence that e-cigarettes act as a gateway to smoking, Reuters reported.

Published in JAMA Pediatrics, the study found that adolescents who have smoked but who also use e-cigarettes were less likely to have given up smoking than those who did not use e-cigarettes. The study’s authors, prominent opponents of e-cigarettes Lauren Dutra and Stanton Glantz, concluded that the "use of e-cigarettes does not discourage, and may encourage, conventional cigarette use among US adolescents."
But critics of the study have commented that its results do not support this conclusion. Dr Michael Siegel, professor of community health sciences at Boston University School of Public Health, commented that while the study did find a correlation between smoking and the use of e-cigarettes, no evidence was found to prove that e-cigarettes were a gateway to smoking. "I could equally argue that what this study shows is that people who are heavy smokers are attracted to e-cigarettes because they are looking to quit," Siegel said.
Funded by the National Cancer Institute and conducted by the University of California San Francisco's Center for Tobacco Control Research and Education, the study’s aim was to better understand the relationship between e-cigarettes, smoking, and smoking cessation among US adolescents.