This study aimed to explore changes in mental health outcomes (depression, anxiety, home, and school stress) from before the first COVID-19 wave (autumn 2019) to the later stages of the same wave (autumn 2020) in a sample of N = 377 Swiss adolescents (Mage = 12.67; 47% female). It also examined whether students' background characteristics (gender, immigrant status, and socio-economic status) and reported COVID-19 burden predicted students' outcomes and their intra-individual changes. Student's mental health, background characteristics, and reported COVID-19 burden were assessed by a self-report questionnaire. The intra-individual changes in students' scores were estimated using random coefficients regression analyses, with time points nested in individuals. To examine the effects of predictors (students' background characteristics and the reported COVID-19 burden) on outcome scores and changes, multilevel intercepts-and-slopes-as-outcomes models were used. The results showed that the expected impact of the pandemic on mental health was not noticeable in the later stages of the first COVID-19 wave. Only two effects were demonstrated in terms of intra-individual changes, namely, an effect of gender on depression and anxiety symptoms and an effect of reported COVID-19 burden on school stress symptoms. Moreover, few associations were found for selected predictors and students' mean level scores, averaged across both time points.
Keywords: COVID-19; adolescence; anxiety; depression; mental health; stress.