Mental health changes during and after the COVID-19 pandemic in children and adolescents with mental disorders.

The COVID-19 pandemic negatively affected child and adolescent mental health, but it is unclear which subgroups were affected most. We investigated to what extent severity and type of mental health problems during and after the pandemic were related to preexisting mental disorders in children in care at child and adolescent mental health services. We employed a repeated cross-sectional design involving data collection at seven time points (April 2020 to April 2023) in a total sample of 2,545 children (age 8-18 years). We grouped diagnostic classifications in four categories: Autism, ADHD, Anxious/Depressive disorders, and 'Other'. Mental health was assessed with parent-reported data on internalizing and externalizing problems and with self-reported data from the standardized PROMIS questionnaires 'Anxiety', 'Depressive symptoms', 'Sleep-related impairments', 'Anger', 'Global health', and 'Peer relations'. We tested for main effects between diagnostic categories and for different trajectories over time. We found that mental health outcomes varied substantially between diagnostic categories, with internalizing problems being largest in children with Anxious/Depressive disorders, and externalizing problems being largest in children with Autism and ADHD. However, we found no evidence for differences between diagnostic categories in trajectories in mental health outcomes during and after the COVID-19 pandemic. The results show that during the pandemic mental health outcomes worsened over time in children and adolescents in care, and that this negative effect on mental health did not differ between children with different diagnostic classifications. Regular high-quality monitoring is vital to recognize changing trajectories of youth mental health and to adapt to crisis situations.