It remains unclear whether children and adolescents in the child welfare system (CWS) exhibit a higher prevalence of mental disorders compared with the general population. The objective of this study was to perform a systematic review and meta-analysis to assess the prevalence of mental disorders in the CWS.A ll of the epidemiological surveys assessing the prevalence of mental disorders in children and adolescents in the CWS were included. The pooled prevalence was estimated with random effect models. Potential sources of heterogeneity were explored using meta-regression analyses.E ight studies provided prevalence estimates that were obtained from 3104 children and adolescents. Nearly 1 child or adolescent of every 2 (49%; 95% confidence interval (CI) 43-54) was identified as meeting criteria for a current mental disorder. The most common mental disorder was disruptive disorder (27%; 95% CI 20-34), including conduct disorder (20%; 95% CI 13-27) and oppositional defiant disorder (12%; 95% CI 10-14). The prevalence of attention-deficit/hyperactivity disorder was estimated to be 11% (95% CI 6-15). The prevalence estimates of anxiety and depressive disorders were 18% (95% CI 12-24) and 11% (95% CI 7-15). Posttraumatic stress disorder had the lowest prevalence (4%; 95% CI 2-6). High prevalences of mental disorders in the CWS were reported, which highlights the need for the provision of qualified service. The substantial heterogeneity of our findings is indicative of the need for accurate epidemiological data to effectively guide public policy.

More than 100 million people have been infected with SARS-CoV-2, and almost 2.5 million have died of COVID-19 worldwide.¹ These numbers probably underestimate COVID-19 deaths by 50% owing to misclassified dementia and cardiovascular or metabolic deaths.² Patients with mental health disorders may be at particular risk of poor COVID-19 outcomes. Patients with mental health disorders can have multiple comorbidities that have been identified as risk factors for severe COVID-19: diabetes, hypertension, chronic obstructive respiratory disease, and end-stage kidney disease.³ Mental health disorders are also associated with socioeconomic deprivation⁴ and reduced access to care,⁵ 2 important factors of poor COVID-19 outcomes.⁶