Recreational screen use and internalizing problems from preadolescence to young adulthood in a longitudinal twin cohort with co-twin comparison.

The mental health impact of increasing recreational screen use among youth has raised substantial concerns, yet questions about causality remain unresolved. Here, leveraging a co-twin control design, we examined associations between screen use and internalizing problems from childhood to early adulthood among 21,797 Swedish twins, accounting for shared familial factors. Recreational screen use was associated with increased internalizing symptoms and clinical diagnosed depression and anxiety. However, these associations were substantially attenuated within discordant twin pairs and did not remain statistically significant after correction for multiple testing. These findings suggest that shared genetic and environmental factors partly explain the association between youth screen use and mental health. Although co-twin estimates provided limited evidence for clear causal effects, the association between heavy interactive screen use and clinical risk highlights the need to understand potential mechanisms linking digital behaviours and youth mental health.