Chadi N, et al. - Researchers conducted this systematic review and meta-analysis to describe and quantify the connection between electronic cigarette (e-cigarette) and marijuana use among adolescents and young adults. From inception to October 2018, PubMed, Embase, and Web of Science & ProQuest Dissertations and Theses were searched. Twenty-one of the 835 studies that were initially listed met selection criteria. The meta-analysis covered three longitudinal studies and 18 cross-sectional studies with 128,227 candidates. In adolescents and young adults who used e-cigarettes, there was a significant increase in the odds of past or current and subsequent marijuana use. Such results emphasize the importance of addressing the rapid increase in youth use of e-cigarettes as a means of helping to reduce the use of marijuana in this population.