Autism Spectrum Disorder Versus Intellectual Disability

Among individuals on the autism spectrum, intellectual disability (ID) is one of the most common co-occurring diagnoses. ID is a neurodevelopmental disorder characterized by impairments in intellectual and adaptive functioning. Such impairments can impact domains implicated in autism spectrum disorder (ASD), such as social communication. Thus, it is essential for diagnosing practictioners to be well-versed in the symptoms and assessment of both ASD and ID, especially in the context of one another. This chapter provides an overview of ID, outlines guiding considerations for differential diagnosis with ASD, and highlights additional needs in a diagnostic assessment when these diagnoses are being evaluated (e.g., evaluation of mental health and behavioral problems).