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

• High levels of gaming, social media use, and TV watching were associated with increased odds of a lifetime diagnosis of depressive, anxiety/stress-related, and hyperkinetic disorders, which closely followed patterns observed for self-reported mental symptoms in healthy adolescents. • A U-shaped pattern emerged with minimal social media engagement also linked to higher odds of any psychiatric diagnosis, potentially reflecting impaired social functioning seen across mental disorders, and particularly neurodevelopmental disorders, which showed the strongest association with the lowest social media use. • Polygenic scores for major depression, anorexia nervosa, attention-deficit hyperactivity disorder, and autism spectrum disorder were significantly associated with screen use, suggesting shared genetic liability. • Associations between moderate-to-high screen use and most diagnoses were substantially confounded by genetic factors, underscoring the importance of integrating genetic perspective in the study of complex behavioural phenotypes. 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 hours/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.