Maartje Boer

CHAPTER 6 154 Abstract Social media have become increasingly integrated into the daily lives of adolescents. There are concerns about the potential detrimental effects of adolescents’ social media use (SMU) on their mental health. Using a three- wave longitudinal study among 2,109 secondary school adolescents ( M age = 13.1, SD age = 0.8), the present study examined whether high SMU intensity and addiction-like SMU problems were bidirectionally associated with low mental health, and whether these associations were mediated by increased levels of upward social comparisons, cybervictimization, decreased subjective school achievements, and less face-to-face contact with friends. In doing so, mental health was measured by depressive symptoms and life satisfaction. Findings from random intercept cross-lagged panel models showed a direct unidirectional association between SMU problems and mental health: SMU problems were associated with decreased mental health one year later, but not vice versa. SMU problems also predicted increased levels of upward social comparisons and cybervictimization one year later. Yet, these processes did not mediate the observed effect of SMU problems on decreased mental health. Over time, SMU intensity and mental health were not associated in any direction, neither directly, nor indirectly through any of the mediators. Findings of our study suggest that harmful effects of SMU intensity may be limited and highlight the potential risk of SMU problems to adolescent mental health. Keywords : social media use, problematic social media use, social media addiction, mental health, adolescents.