How does social tie strength work? A panel study exploring the effects of pro-e-cigarette content from peers, influencers, and brands on social media

Previous large-scale and experimental studies indicate that pro-e-cigarette content on social media is prevalent and fosters adolescents' positive attitudes and smoking behaviors. However, the influence of different information sources on social media remains understudied. Guided by social tie strength theory, this study investigates the longitudinal effects of pro-e-cigarette content from three sources—peers, influencers, and brands. Panel data from Waves 6 (T1, 2021–2022) and 7 (T2, 2022–2023) of the Population Assessment of Tobacco and Health (PATH) Study were analyzed. Youth aged 12–17 who were non-e-cigarette users at T1 were included (n = 613). Using mediation analysis, this study examined the effects of exposure to pro-e-cigarette content from peers, influencers, and brands on perceived social norms and e-cigarette susceptibility. The results suggested different sources had distinct effects. T1 exposure to pro-e-cigarette content from peers increased perceived e-cigarette social norms (b = .122, p < .05), which in turn led to greater e-cigarette susceptibility at T2 (OR = 1.589, p < .01). While exposure to influencer content did not significantly affect perceived social norms, it directly increased e-cigarette susceptibility at T2 (OR = 1.433, p < .05). Brand exposure showed no effect on perceived social norms or e-cigarette susceptibility. The strength of social ties can affect perceived social norms and susceptibility to e-cigarettes among youth, with stronger ties exerting a more pronounced impact. These findings offer insights for policymakers and media planners in designing e-cigarette educational campaigns via different social media sources.