Cannabis expectancies mediate the association between social media use and cannabis experimentation in early adolescents: A prospective cohort study.

BACKGROUND: Social media exposure may influence early cannabis use behaviors in adolescents, potentially increasing the risk of future problematic use. Minimal prior research has investigated the role of cannabis expectancies (i.e., beliefs about the anticipated positive or negative effects of cannabis) and their role in mediating cannabis use initiation in early adolescence. OBJECTIVE: To examine the prospective association between social media use and cannabis experimentation in a diverse U.S. sample of early adolescents, and to determine the extent to which cannabis expectancies mediate this relationship. METHODS: We utilized longitudinal data from the Adolescent Brain Cognitive Development Study (N = 7691, mean age 12.0 at Year 2 follow-up, 2018-2020) to estimate associations between daily social media time (Year 2) and cannabis use outcomes (Year 4) using sequential modeling approaches, adjusting for confounders including friends' cannabis use, and testing cannabis expectancies (Year 3) as a mediator. RESULTS: Social media time (Year 2) was significantly associated with cannabis experimentation (Year 4) (B = 0.18, 95 % CI: 0.13-0.24, p < 0.001). At Year 3, positive cannabis expectancies predicted higher likelihood of experimentation one year later, while negative expectancies predicted lower likelihood. Positive cannabis expectancies mediated 19.8 % and negative cannabis expectancies mediated 13.6 % of the social media-cannabis use association. CONCLUSIONS: Given the association between social media exposure on cannabis use and the mediating role of expectancies for adolescents, future research may explore interventions that limit both social media time and address expectancies to prevent early initiation of cannabis use.