Teens who use e-cigarettes are at higher risk of transitioning to smoking conventional cigarettes than their peers who don’t use vaping devices, a new report concludes.

The findings, from the National Academies of Sciences, Engineering and Medicine, is the most comprehensive analysis of existing research on e-cigarettes, according to The New York Times.

“E-cigarettes cannot be simply categorized as either beneficial or harmful,” David Eaton, chair of the committee that wrote the report, said in a news release. “In some circumstances, such as their use by non-smoking adolescents and young adults, their adverse effects clearly warrant concern. In other cases, such as when adult smokers use them to quit smoking, they offer an opportunity to reduce smoking-related illness.”