Importance Social media’s association with adolescent well-being remains debated. Heavy use has been associated with distress, while abstinence may cause missed connections. Objective To investigate 3-year longitudinal associations between after-school social media use and adolescent well-being using a large longitudinal cohort dataset modeled within a repeated cross-sectional framework. Design, Setting, and Participants This cohort study included Australian students in grades 4 through 12 (2019-2022). After-school social media use was self-reported and grouped as none, moderate, or highest. Well-being was assessed using 8 validated indicators (eg, happiness, life satisfaction, emotional regulation), dichotomized as high vs low. Well-being was assessed concurrently with social media use during the annual school-based survey in each year of data collection. Data analysis was conducted from June to July 2025. Exposures Self-reported after-school social media use between 3 pm and 6 pm (weekdays), classified into 3 categories: none (0 h/wk), moderate (gt;0 to lt;12.5 h/wk), and highest (≥12.5 h/wk). Main Outcomes and Measures The primary outcome was overall well-being, measured as the mean score across 8 validated domains (happiness, optimism, life satisfaction, worry, sadness, perseverance, emotional regulation, and cognitive engagement), dichotomized as high vs low (lt;3 on a scale of 1-5). Secondary outcomes were each individual well-being indicator, similarly dichotomized. Mixed-effects logistic models were used for analyses, stratified by sex and adjusted for demographic covariates. Results The analytic sample included 100 991 adolescents, contributing 173 533 observations (86 582 49.9% observations from female participants; mean SD age, 13.5 2.2 years). A U-shaped association was observed between after-school social media use and well-being. Compared with moderate users, adolescents with the highest use had greater odds of low well-being (grades 7-9, girls: odds ratio OR, 3.13 95% CI, 2.88-3.39; boys: OR, 2.25 95% CI, 1.86-2.72), while nonusers also had higher odds of low well-being in later adolescence (grades 10-12, girls: OR, 1.79 95% CI, 1.41-2.27; boys: OR, 3.00 95% CI, 2.01-4.46). These patterns were consistent across survey years and robust to sensitivity analyses. Conclusions and Relevance In this cohort study of students in grades 4 through 12, social media’s association with adolescent well-being was complex and nonlinear, varying by age and sex. While heavy use was associated with poorer well-being and abstinence sometimes coincided with less favorable outcomes, these findings are observational and should be interpreted cautiously.
Singh et al. (2026) studied this question.