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

Background

Digital devices have become a major aspect of children’s life. Associations between screen time and mental health have been observed, but the causality remains unclear. This study aimed to investigate the associations between screen time and later depressive symptoms, and to test the robustness of these associations when accounting for genetic confounding.

Methods

This 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. Average daily screen time was calculated. Depressive symptoms were measured using the Short Mood and Feelings Questionnaire (SMFQ). Polygenic scores for depression were calculated. Linear regression models were used to examine the associations between standardised 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.

Results

A total of 3,003 participants were included in analysis. Some, but not all, forms of screen time were associated with higher SMFQ scores, e.g. time spent using a phone, tablet, or e-book at age 22 (β: 0.10 [95%CI 0.07, 0.14] for weekdays; β: 0.08 [0.04, 0.11] for weekends) and television time at age 26 (β: 0.10 [95%CI 0.06, 0.14] for weekdays; β: 0.09 [0.06, 0.13] for weekends). These associations persisted after adjusting for sociodemographic confounders and polygenic scores but were attenuated in the genetic sensitivity analysis (β=0.03 [-0.01, 0.07] for the association with time spent using a phone, tablet, or e-book at age 22 on weekends; β=0.06 [0.01, 0.10]) for television time at age 26 on weekends).

Conclusions

For some measures of screen time, there were no associations with depressive symptoms. Where associations were seen, they were attenuated in genetic sensitivity analysis, implying genetic confounding is present in the relationship between screen time and depressive symptoms in adolescents and young adults.

Key Messages

• This study investigated the associations between screen time and later depressive symptoms during adolescence and early adulthood, using a range of approaches to examine confounding, including a genetic sensitivity model.

• Genetic confounding plays a role in the relationship between different types of screen time and depressive symptoms in adolescents and young adults, with the relationship between excessive screen time and depressive symptoms appearing weaker after accounting for genetic confounding.

• This study suggests that genetic confounding is present in the relationship between screen time and depressive symptoms in adolescents and young adults, highlighting the need to consider genetic factors when interpreting this association.