To Örebro University

The mental health impact of increasing recreational screen use among youth has raised substantial concerns, yet questions about causality remain unresolved. Using data from ~22,000 Swedish twins followed from age 9 to 24, we examined associations between screen use and internalizing problems using multiple designs, including co-twin control comparisons, to strengthen causal inference. Associations between longer screen time and elevated internalizing symptoms during adolescence persisted in co-twin comparisons, supporting a potential causal link. Bidirectional associations were observed, with internalizing problems at younger ages also associated with later screen time increase. Adolescents who exceeded international screen time recommendations at ages 15 and 18 showed elevated internalizing symptoms at later ages, whereas those who reduced screen time to recommended levels did not. Heavy screen use at age 15, particularly during the weekdays, was associated with higher risk of clinical depression or anxiety. Findings support public health recommendations to limit recreational screen time.