Intellectual disability (ID), formerly known as mental retardation, is a neurodevelopmental disorder that onsets early in childhood and entails significant deficits in both intelligence and adaptive skills, including one’s ability to independently manage common life demands. An array of factors are linked to the causes of ID, including genetic conditions, severe neglect, and various medical complications (e.g., brain injury), all of which can hinder normal brain development. ID is a disorder [Page 829]that can be a standalone diagnosis, part of a collection of symptoms (i.e., syndrome), or it can co-occur with other neurodevelopmental (e.g., autism spectrum disorders), medical (e.g., cerebral palsy), and psychiatric (e.g., schizophrenia) conditions.

Given the severe, pervasive, and diverse nature of impairments that are associated with ID, it is essential that psychologists and ...