Longitudinal trajectories of ADHD-like symptoms across adolescence and associations with problematic smartphone use: Evidence from a five-wave cohort study.

Adolescence is a period of marked change in mental health symptoms, yet longitudinal evidence on the developmental course of ADHD-like symptoms and their behavioral correlates remains limited. Using five-wave data from a Chinese accelerated cohort (N = 3414), we estimated nonlinear age-related trajectories of total ADHD-like symptoms and subdimensions (hyperactivity, attention deficit, impulsivity) from ages 10-18. Problematic smartphone use (PSU) was examined through cross-lagged time-varying associations in both directions and through latent trajectory groups. ADHD-like symptoms followed a U-shaped pattern, declining in early adolescence and increasing in later adolescence. Sex and subjective socioeconomic status were primarily associated with baseline differences, with higher initial severity among boys and lower-SES adolescents. Higher PSU at the preceding wave predicted higher subsequent ADHD-like symptoms across domains. Long-term PSU patterns were most clearly expressed in hyperactivity: adolescents in the persistently high PSU trajectory group exhibited the greatest symptom burden and a stronger late-adolescent upturn in this domain. Within this observational design, sustained high PSU was associated with-rather than shown to cause-elevated ADHD-like symptom trajectories across adolescence, and may index a potentially modifiable behavioral correlate warranting further study.