BackgroundThe aim of this study is to examine the prevalence of mental disorders in 6- to 12-year-old foster children and assess comorbidity and risk factors.MethodsInformation on mental health was collected from foster parents and from teachers using Developmental and Well-Being Assessment (DAWBA) Web-based diagnostic interview. Child welfare services provided information about care conditions prior to placement and about the child’s placement history.ResultsDiagnostic information was obtained about 279 (70.5%) of 396 eligible foster children. In total, 50.9% of the children met the criteria for one or more DSM-IV disorders. The most common disorders were grouped into 3 main diagnostic groups: Emotional disorders (24.0%), ADHD (19.0%), and Behavioural disorders (21.5%). The comorbidity rates among these 3 main groups were high: 30.4% had disorders in 2 of these 3 diagnostic groups, and 13.0% had disorders in all 3 groups. In addition, Reactive attachment disorder (RAD) was diagnosed in 19.4% of the children, of whom 58.5% had comorbid disorders in the main diagnostic groups. Exposure to violence, serious neglect, and the number of prior placements increased the risk for mental disorders.ConclusionsFoster children in Norway have a high prevalence of mental disorders, compared to the general child population in Norway and to other societies. The finding that 1 in 2 foster children presented with a mental disorder with high rates of comorbidity highlight the need for skilled assessment and qualified service provision for foster children and families.