Reciprocal relationship among perceived sleep quality, smartphone overdependence, and depression in Korean adolescents: a cross-lagged analysis using national big data

Adolescent depression is a critical public health concern, with growing links to excessive smartphone use and perceived poor sleep quality. However, the reciprocal relationships among these factors remain poorly understood. This longitudinal study examined the directional and temporal pathways linking smartphone overdependence, sleep quality, and depressive symptoms over time. Data were drawn from the Korea Children and Youth Panel Survey, including 2,052 adolescents who completed three consecutive waves from 2020 to 2022. Smartphone overdependence was measured using the Smartphone Addiction Self-Diagnosis Scale, perceived sleep quality was assessed with a single item developed by the National Institute of South Korea, and depressive symptoms were evaluated using the 13-item Brief Psychiatric Diagnostic Test. An autoregressive cross-lagged panel model was used to evaluate temporal and predictive relationships among these variables. The analysis revealed that poor sleep quality consistently predicted later smartphone overdependence and depressive symptoms. Depressive symptoms also predicted declines in sleep quality, indicating a bidirectional relationship. These findings highlight the importance of sleep as a central target for integrated interventions and may inform broader mental health policies aimed at improving adolescent well-being.