A Longitudinal Study of the Relationship between Marijuana, E-Cigarette, and Cigarette Use in Youth

Background. There is emerging evidence linking youth use of Electronic (e-) cigarettes to subsequent cigarette and marijuana use, raising public health concerns.

Methods. We collected self-reports from 1,165 Oregon adolescents (52% female; 36% Hispanic) longitudinally from 8^th to 11^th grade (8 total surveys) regarding their lifetime (ever use) and current use (last 30 days) of marijuana, e-cigarettes, and conventional cigarettes. If applicable, students also reported the delivery method of their current marijuana use.

Results. At the time of the baseline 8^th grade survey, 32% of students had already tried all three substances. By the 11^th grade, 46% reported lifetime use of marijuana, 48% reported lifetime use of e-cigarettes, and 40% reported lifetime use of cigarettes. More students transitioned from e-cigarettes to marijuana than to conventional cigarettes, and e-cigarettes were the first substance used for most students who initiated use during the study. Participants who were co-using marijuana and e-cigarettes in 11^th grade had an increased likelihood of consuming marijuana via vaping, dabbing, and edibles, compared to those who were only using marijuana.

Conclusions. Co-use of substances was quite high. E-cigarettes were the first substance used for about 14% of youth in this sample, and more of these youth subsequently used marijuana than cigarettes. While research has focused on the progression from e-cigarettes to conventional cigarettes in youth, these findings indicate that more attention should be focused on the subsequent initiation of marijuana.