Impact of the COVID-19 pandemic on the mental health of children and adolescents: A systematic review and meta-analysis of longitudinal studies

Background: Children's and adolescents' mental health has been affected since the onset of the coronavirus disease (COVID-19) pandemic, receiving global attention. We conducted a systematic review and meta-analysis of longitudinal studies to assess the extent of the mental health changes of children and adolescents in the aftermath of the pandemic.Methods: We searched PubMed, Embase, Web of Science, and PsycINFO to explore the pandemic's impact on children and adolescents' mental health; longitudinal studies were included. We used the random effects model to estimate the standardized mean differences (SMD) with 95 % confidence intervals (CI).Results: Twenty articles were included. Results showed that there was an increase in anxiety (SMD = 0.18, 95 % CI 0.05-0.32) and depressive symptoms (SMD = 0.22, 95 % CI 0.13-0.32) in children and adolescents after the pandemic. Anxiety and depressive symptoms noticeably increased from April to May 2020, subsequently decreased, but saw a small resurgence during the second wave of the pandemic. Anxiety change varied by region; highest in Asia (SMD = 0.38, 95 % CI 0.25-0.51).Limitations: Heterogeneity was high in this study, with high variability in psychiatric symptoms among individuals.Conclusions: This study on changes in children's and adolescents' mental health, anxiety and depression symp-toms showed varying degrees of deterioration. Changes in symptoms were influenced by time and region and showed fluctuations.