Exploring genetic confounding of the associations between excessive screen time and depressive symptoms in adolescence and early adulthood

BackgroundDigital devices have become a major aspect of childrens life. Associations between screen time and mental health have been observed, but the causality remains unclear. This study aimed to investigate the associations between excessive screen time and later depressive symptoms, and to test the robustness of these associations when accounting for genetic confounding. MethodsThis study used data from the Avon Longitudinal Study of Parents and Children (ALSPAC), a prospective cohort of children born between 1991 and 1992 in the UK. Different forms of screen time and depressive symptoms at ages 16, 22 and 26 were assessed through self-completion questionnaires. Screen time > 2 hours per day was defined as excessive. Depressive symptoms at age 26 were measured using the Short Mood and Feelings Questionnaire (SMFQ). Polygenic scores for mental health problems were calculated. Linear regression models were used to examine the associations between screen time at ages 16, 22 and 26 and depressive symptoms at age 26, adjusting for sociodemographic confounders and polygenic scores. Genetic sensitivity analysis (Gsens) was used to test for genetic confounding in these associations. ResultsA total of 3,005 participants were included in analysis. Some, but not all, forms of excessive screen time were associated with higher SMFQ scores, e.g. more than 2 hours of television time per day at age 16 ({beta}: 0.07 [95%CI 0.04, 0.11] for weekdays; {beta}: 0.06 [0.02, 0.09] for weekends) and more than 2 hours of gaming time at age 22 ({beta}: 0.07 [95%CI 0.03, 0.10] for weekdays; {beta}: 0.07 [0.04, 0.11] for weekends). These associations persisted after adjusting for sociodemographic confounders and polygenic scores but were attenuated to the null in the genetic sensitivity analysis ({beta}=0.02 [-0.02, 0.06] for the association with >2 hours of television time at age 16 on weekdays; {beta}=-0.01 [-0.05, 0.03]) for >2 hours of gaming time at age 22 on weekdays). ConclusionsFor most measures of screen time, there were no associations with depressive symptoms. Where associations were seen, they were completely attenuated in genetic sensitivity analysis, implying genetic confounding is present in the relationship between excessive screen time and depressive symptoms in adolescents and young adults.