Intellectual Disability, Autism Spectrum Disorders, Psychiatric Comorbidities and Their Relationship with Challenging Behavior

Background The purpose of this study was to assess the prevalence of unknown comorbid mental disorders in individuals with mild/moderate intellectual disability (ID) with/without autism spectrum disorders (ASD) and to compare the severity of challenging behavior with respect to the comorbidity of ASD and comorbid psychiatric disorders. Methods This is a cross-sectional study of 91 adults with mild or moderate ID with no previous psychiatric diagnosis (except ASD). The assessment tools were the PAS-ADD checklist, Mini-PAS-ADD, PAS-ADD clinical interview and the Inventory for Client and Agency Planning (ICAP). Results A previously undiagnosed mental disorder was found in 23.81% of the individuals with ID and ASD and in 10.20% of the individuals without. The most prevalent mental disorder was major depressive disorder. An association between psychiatric comorbidity and challenging behavior was found in people with ID and ASD. Conclusions The prevalence of underdiagnosed mental disorders in individuals with ASD and ID is high and is associated with challenging behavior.