Intellectual Disability and Mental Retardation

A Change in Terminology

The term mental retardation lost favor in the United States during the early 2000s. This change became prevalent in the naming of advocate organizations (e.g., the American Association on Mental Retardation became the American Association on Intellectual and Developmental Disabilities), and in scholarly works as well. While the terms intellectual disability and mental retardation are essentially synonymous, intellectual disability conveys a different construct, and provides an inoffensive way to discuss individuals who have subaverage intellectual abilities and face challenges in their adaptive behaviors. Another rationale for the transition from mental retardation to intellectual disabilities is to dissociate individuals with intellectual disabilities from the prevalent, pejorative use of the word retarded. It is important to note, however, that the term mental retardation is still used in U.S. federal law, and appears in almost all legislation, such as the Individuals with Disabilities Education Act (IDEA).

Defining Intellectual Disabilities

According to the American Association on Intellectual and Developmental Disabilities (AAIDD), an individual with an intellectual disability has a significantly below-average IQ and faces challenges in adaptive functioning. These challenges can occur within their daily living skills, social skills, and conceptual skills. Specifically, IQ ranges of 70 (sometimes up to 75) to 50 or 55 are considered a mild intellectual disability, IQ scores from 50/55–35/40 indicate a moderate intellectual disability, scores between 35/40 and 25/30 indicate severe intellectual disability, and an IQ below 20/25 is indicative of a profound intellectual disability. The AAIDD also classifies intellectual levels according to the level of support an individual needs: intermittent, limited, extensive, and pervasive (i.e., constant). Within schools, however, these categories are broadened and more generalized. Children with an IQ roughly between 55 and 70 are classified as “mildly intellectually disabled.” This level of disability is typically considered a high incidence disability, meaning it occurs more frequently in the population. Accordingly, Edward A. Polloway, Jacqueline Lubin, J. David Smith, and James R. Patton posit that at least half of all students with intellectual disabilities would be classified as having a mild intellectual disability. Schools classify students with IQ scores below 55 as having moderate or severe intellectual disability. Because the incidences of moderate and severe intellectual disability are both significantly lower than the more than 50% attributed to the “mild” category alone, they are considered low incidence disabilities.

The difference between mild and moderate or severe intellectual disabilities involves more than IQ points. Because of the severity of the developmental challenges faced by children with low incidence disabilities, they are typically identified at birth or early in their lives, and the diagnosis itself is considered an objective one. Conversely, high incidence disabilities can often go undiagnosed in children until they enroll in school. Subsequently, [Page 1203]their identification can be more difficult, as they are seen as subjective and vulnerable to bias.

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