How Does Social Media Make Adolescents Lonely? Social Capital and Social Comparison as Heterogeneous Within-Person Mediators

Social media is often blamed for the “epidemic” of loneliness facing today’s adolescents, yet evidence remains mixed. Drawing on the extended active–passive social media use model, the current study tested two potential mechanisms linking social media use to adolescent loneliness—social capital and social comparison. Using a three-week experience-sampling study of 387 adolescents (Nobs = 35,356), we employed dynamic structural equation modelling to conduct longitudinal, within-person, and person-specific mediation analyses. Contrary to theoretical predictions, when adolescents engaged in more active social media use (e.g., messaging) than usual, they reported greater loneliness, and this effect was mediated by lower social capital. Supporting theoretical predictions, when adolescents engaged in more passive social media use (e.g., scrolling) than usual, they reported greater loneliness, and this effect was mediated by greater social comparison. Both indirect effects displayed significant heterogeneity across adolescents, and meaningful effects were concentrated among a subset of adolescents. Exploratory analyses also revealed that indirect effects varied over time within adolescents. Given the prevalence of adolescent loneliness, it is highly concerning that both active and passive social media use may contribute to this pressing issue. The mediating roles of social capital and social comparison suggest avenues for interventions to promote healthy social media use. Finally, between-person and across-time heterogeneity in effects highlights the need to avoid one-size-fits-all conclusions about social media and adolescent loneliness, and to consider individual difference and contextual factors that drive social media effects.