Age-related effects of the COVID-19 pandemic on mental health of children and adolescents.

: Children and adolescents are affected in various ways by the lockdown measures due to the COVID-19 pandemic. Therefore, it is crucial to better understand the effects of the COVID-19 pandemic on mental health in this age-group. : The objective was to investigate and compare the effects of the COVID-19 pandemic on mental health in three age groups (1-6 years, 7-10 years, 11-19 years) and to examine the associations with psychological factors. : An anonymous online survey was conducted from 9 April to 11 May 2020 during the acute phase of major lockdown measures. In this cross-sectional study, children and adolescents aged between 1 and 19 years were recruited as a population-based sample. They were eligible if they were residents in Austria, Germany, Liechtenstein or Switzerland, were parents/caregivers of a child aged between 1 and 10 years or adolescents ≥11 years, had sufficient German language skills and provided informed consent. : Among 5823 participants, between 2.2% and 9.9% reported emotional and behavioural problems above the clinical cut-off and between 15.3% and 43.0% reported an increase in these problems during the pandemic. Significant age-related effects were found regarding the type and frequency of problems (χ ≥50.2, ≤ 0.001). While preschoolers (1-6 years) had the largest increase in oppositional-defiant behaviours, adolescents reported the largest increase in emotional problems. Adolescents experienced a significantly larger decrease in emotional and behavioural problems than both preschoolers and school-children. Sociodemographic variables, exposure to and appraisal of COVID-19, psychotherapy before COVID-19 and parental mental health significantly predicted change in problem-scores (F ≥ 3.69, ≤ 0.001). : A substantial proportion of children and adolescents experience age-related mental health problems during the COVID-19 pandemic. These problems should be monitored, and support should be offered to risk-groups to improve communication, emotion regulation and appraisal style.