The phenotypic and genetic relationship between adolescent mental health and time spent on social media, gaming, and TV.

Screen use is linked to adverse mental health outcomes in adolescents, but how associations vary across psychiatric diagnoses, mental symptoms, and types of screen-based activities remain unclear. The contribution of genetic factors to these associations is also largely unknown. We analysed data from 23,790 adolescents (aged 14-16) in the Norwegian Mother, Father, and Child Cohort Study (MoBa), linking questionnaire responses on screen use to registry-based psychiatric diagnoses and self-reported symptoms. Using regression models, we assessed associations between mental health outcomes and gaming, social media use, and TV watching. We also evaluated whether genetic liability to psychiatric disorders, as indexed by polygenic scores (PGSs), was associated with screen use, and estimated the degree of genetic confounding. Spending 3-4 h/day or more on any screen-based activity was associated with increased odds of a lifetime diagnosis of depressive, anxiety/stress-related, and hyperkinetic disorders. Similarly, minimal social media engagement was associated with increased odds of psychiatric diagnoses, particularly pervasive developmental disorders. Associations with self-reported symptoms closely followed those observed for clinical diagnoses. PGSs for major depression, anorexia nervosa, attention-deficit hyperactivity disorder, and autism spectrum disorder were associated with screen use, suggesting shared genetic liability. Moreover, a substantial proportion of the phenotypic associations appeared to be attributable to genetic confounding. Our findings suggest a complex, bidirectional relationship between screen use and adolescent mental health. Both high and low screen use may reflect underlying mental health vulnerabilities, with shared genetic susceptibility playing an important role. These results support the need for individualized, context-sensitive screen use guidelines.