BackgroundYoung adults are more vulnerable than older adults to engagement with online tobacco marketing and to the use of electronic nicotine delivery systems (ENDS) products. Our study examined the longitudinal associations between engagement with pro- and anti-tobacco information on social media (SM) and young adults’ subsequent onset of symptoms of dependence on ENDS products one year later, which remain unclear. MethodsParticipants were college students in the Marketing and Promotions Across Colleges in Texas study. We analyzed data collected in spring 2018 (wave 8, baseline) and spring 2019 (wave 9), which involves 1,764 college students (Mean age = 24.48, 34.8% White) who reported having ever used any ENDS products but no ENDS dependence symptoms at baseline. Logistic regression analyses were conducted to examine the associations between pro- and anti-engagement with tobacco information at baseline and onset of ENDS dependence symptoms at one-year follow-up, controlling for baseline sociodemographic characteristics and tobacco smoking status. We also examined participant sex and depressive symptoms as moderators of the aforementioned associations. ResultsEngagement with both pro- (Odds Ratio = 1.73, p < 0.05) and anti- (Odds Ratio = 1.36, p < 0.05) tobacco information at baseline predicted the subsequent onset of symptoms of dependence on ENDS products one year later. The association between pro-engagement and subsequent onset of ENDS dependence symptoms was stronger among females than males (Exp(β) = 3.21, p < 0.05). Depressive symptomology did not moderate any of the associations. ConclusionsFindings suggest that engaging with tobacco information on SM, regardless of its valence, serves as a risk factor for the development of subsequent dependence symptoms among young adult ever ENDS users. Considering the uncertainty of ENDS products’ health effects, regulation of SM is encouraged to reduce young adults’ (re)posting thoughts or comments about the advantages of ENDS products.