Abstract
BACKGROUND: Rising internalizing problems (e.g., depression and anxiety) among youth, particularly among females, have raised concerns about potential societal causes. Social media use (SMU) has emerged as a key focus, given its widespread adoption since the early 2010s. While small to moderate correlations are typically reported between SMU and internalizing problems on the individual level, a complementary community-based perspective allows for assessing the effects of living in environments with high or low social media use on youth mental health. METHODS: This study investigates the effect of SMU on internalizing symptoms among Norwegian youth in a longitudinal study at the municipality level. The study uses data from the nationwide Ungdata surveys (2014-2024), covering 528 cohorts across 181 municipalities, comprising 40 014 individual responses. Anxiety and depressive symptoms were assessed using items adapted from the Hopkins Symptom Checklist and the Depressive Mood Inventory, respectively. We applied a Bayesian multilevel model, accounting for time-varying and time-constant confounders. RESULTS: An additional hour of average SMU corresponded to a 0.70 [0.26, 1.14] SD increase in anxiety scores for boys but showed no clear association for girls (-0.03 [-0.31, 0.24]). For depressive symptoms, a one-hour increase in average SMU corresponded to an increase of 0.25 [0.03, 0.46] for boys, with no clear effect for girls (0.02 [-0.15, 0.19]). The models accounted for a substantial proportion of variance in T2 outcomes (r² = 0.6 - 0.8). CONCLUSION: Assuming that all relevant factors influencing both social media use and youth mental health were accounted for, the findings suggest that living in municipalities with high social media use may have a small effect on youth mental health among boys, while no effect was observed among girls.