Most of the studies that examine the effect of the COVID-19 pandemic on mental health have been restricted to pandemic mental health data alone. The aim of the current study was to estimate the pandemic's effect on young Swiss adults' mental health by comparing pandemic to pre-pandemic mental health. Longitudinal data of 1175 young Swiss adults who participated in the S-YESMH study in 2018 and were followed-up in 2020 and 2021 were analyzed. The study outcomes were self-reported symptoms of depression, generalized anxiety disorder (GAD), attention-deficit/hyperactivity disorder (ADHD), thoughts about death or self-harm, and risky single-occasion drinking (RSOD). Generalized estimation equations, logistic regression and statistical mediation analysis were used to analyze the data. Evidence was found of increased depression, GAD, and ADHD among young women and increased depression among young men, resulting from the COVID-19 pandemic. Uncertainty about the future predicted young women's depression and anxiety in 2021. COVID-19 stress in 2021 fully mediated the effect of COVID-19 stress in 2020 on depression and GAD in 2021. Young Swiss women's and men's mental health appears to have been adversely affected by the COVID-19 pandemic, especially during the second pandemic year. Uncertainty about the future and stress becoming chronic in 2021 likely explain some of the adverse effects.
Keywords: COVID-19; alcohol drinking; anxiety; attention-deficit/hyperactivity disorder; depression; young adults.