Smartphones, Peer Relationships, and Depressive Symptoms: A Six-Year Growth Model of Adolescent Mental Health

From a media psychology perspective, understanding how digital behaviors influence mental health requires attention to individual differences and changes over time. This study examined longitudinal associations among smartphone use, peer relationships, and depressive symptoms using six waves of the Korean Children and Youth Panel Survey 2018 (KCYPS 2018), a nationally representative panel of South Korean adolescents (N = 2,460; ages 10–15). Multilevel growth modeling distinguished between- and within-person components of smartphone use and peer relationships. Higher average smartphone use and within-person increases in smartphone use were associated with higher depressive symptoms. More positive peer relationships were associated with lower depressive symptoms at both levels. Although within-person fluctuations in peer relationships did not consistently moderate the association between within-person smartphone use and depressive symptoms, this moderating role changed over time. Specifically, more positive-than-usual peer relationships showed an increasingly pronounced buffering pattern in this association across adolescence. Gender differences were also observed: girls reported higher baseline depressive symptoms, whereas boys showed steeper increases over time. These findings demonstrate the importance of distinguishing between- and within-person processes and considering adolescents’ social contexts when examining associations between smartphone use and mental health.