Abstract
As an extension of a previous cross-sectional study, this study employed prospective data to test positive outcome expectancy beliefs as mediators of social media's influence on e-cigarette use progression among young adults. Self-report data were collected from 2327 young adult college students (Mean age = 21.2; SD = 2.1; 54% women) between 2017 and 2019, every 6-month, at 3 time-points. Structural equation modeling was used to test the mediational models. Among baseline never e-cigarette users, higher affect regulation expectancies-e.g., beliefs that e-cigarette use results in feeling good, reduced boredom and stress-mediated the effects of higher baseline social media e-cigarette exposure on e-cigarette use onset one year later. Among baseline lifetime e-cigarette users, higher positive sensory, positive "smoking" experience, and affect regulation expectancy beliefs mediated the effects of higher social media e-cigarette exposure at baseline on increased current e-cigarette use one year later. E-cigarette content on social media may persuade young adults to try e-cigarettes by imparting the sense that e-cigarettes make one feel good and help reduce stress. E-cigarette content on social media that promote e-cigarette flavors and e-cigarettes as cleaner and a socially more acceptable alternative to cigarettes may work to escalate e-cigarette use among experimenters. Efforts to prevent e-cigarette use onset and escalation may need to target the outcome expectancy beliefs influenced by social media.