Screen time and adolescents' mental health before and after the COVID-19 lockdown in Switzerland: A natural experiment.

Background: During the COVID-19 lockdown in 2020, adolescents' mental health was largely undermined. A general increment in screen time was reported. However, the long-term effects of the latter on adolescents' mental health are still little explored.

Methods: In the present natural experiment, we investigated these effects using longitudinal data collected before and after the first lockdown in Switzerland. Data come from 674 Swiss adolescents (56.7% females, M = 14.45, SD = 0.50) during Spring 2019 (T1) and Autumn 2020 (T2) as part of the longitudinal MEDIATICINO study. Self-reported mental health measures included somatic symptoms, inattention, anxiety, irritability, anger, sleep problems, obsessive-compulsive symptoms, loneliness, and depression. Measures for screen-media activities included time spent on the Internet, smartphones, social media, video gaming, instant messaging, and television viewing. They were all assessed at T1 and T2.

Results: Paired-sample -tests with Bonferroni's correction showed that most mental health problems increased over time with an overall medium effect size (Hedge's = 0.337). In particular, medium effect sizes were found for anxiety, depression, and inattention; small-to-medium effect sizes were reported for loneliness, sleep problems, and obsessive-compulsive symptoms; and a small effect size was found for somatic symptoms. Screen-media activities increased, with the exception of television viewing and video gaming. The results of the hierarchical regression analyses showed that, controlling for covariates, increased time spent on social media - calculated as the difference between T2 and T1 - was the only screen-media activity significantly associated with worse mental health at T2 (β = 0.112, = 0.016). More time spent in structured media activities like television viewing diminished levels of inattention (β = -0.091, = 0.021) and anxiety (β = -0.093, = 0.014). Among covariates, being female, experiencing two or more life events, having mental health problems at T1, and using screens for homeschooling negatively influenced mental health at T2.

Conclusion: These results align with literature indicating a small but negative effect of social media time on mental health. Underlying mechanisms are manifold, including increased exposure to COVID-19 news, heightened fear of missing out, social comparison, and time-displaced for activities such as physical activity and green time. However, in line with the , getting involved in media-structured activities like television viewing might protect against mental health symptoms.