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Intellectual disability is a disability that occurs before age 18. People with this disability experience significant limitations in two main areas: 1) intellectual functioning and 2) adaptive behavior. These limitations are expressed in the person’s conceptual, social and practical everyday living skills. A number of people with intellectual disability are mildly affected, making the disability difficult to recognize without visual cues. Intellectual disability is diagnosed through the use of standardized tests of intelligence and adaptive behavior. Individuals with intellectual disabilities who are provided appropriate personalized supports over a sustained period generally have improved life outcomes (AAIDD, 2011). In fact, many adults with intellectual disabilities can live independent, productive lives in the community with support from family, friends and agencies like The Arc.

According to the Developmental Disabilities Act (Pub. L. 106-402), the term developmental disability means a severe, chronic disability that:

1. is attributable to a mental or physical impairment or a combination of those impairments;
2. occurs before the individual reaches age 22;
3. is likely to continue indefinitely;
4. results in substantial functional limitations in three or more of the following areas of major life activity: (i) self care, (ii) receptive and expressive language, (iii) learning, (iv) mobility, (v) self-direction, (vi) capacity for independent living, and (vii) economic self-sufficiency; and
5. reflects the individual’s need for a combination and sequence of special, interdisciplinary, or generic services, individualized supports, or other forms of assistance that are of lifelong or extended duration and are individually planned and coordinated.

Before the age of ten, an infant or child with developmental delays may be considered to have an intellectual or developmental disability if his or her disabilities are likely to meet the above criteria without intervention.

The major differences are in the age of onset, the severity of limitations, and the fact that the developmental disability definition does not refer to an IQ requirement. Many individuals with intellectual disability will also meet the definition of developmental disability. However, it is estimated that at least half of individuals with intellectual disability will not meet the functional limitation requirement in the DD definition. The DD definition requires substantial functional limitations in three or more areas of major life activity. The intellectual disability definition requires significant limitations in one area of adaptive behavior.

Those with developmental disabilities include individuals with cerebral palsy, epilepsy, developmental delay, autism and autism spectrum disorders, fetal alcohol spectrum disorder (or FASD) or any of hundreds of specific syndromes and neurological conditions that can result in impairment of general intellectual functioning or adaptive behavior similar to that of a person with intellectual disabilities.

The term “mental retardation” is an out-dated term that may offer special protections in some states, however, with the passage of Rosa’s Law in 2010, many states have replaced all terminology from mental retardation to intellectual disability. Although some still use the term “mental retardation” to be eligible for some services in a few states, in no case does having the label guarantee that supports will be available. The general public, including families, individuals, funders, administrators, and public policymakers at local, state and federal levels, are becoming aware of how offensive this term is and are actively working to make sure the public at large now use the preferred term of intellectual or developmental disability.

Note: the information and definitions noted above are subject to change as public laws are revised, diagnostic and evaluative methods change, and contemporary terminology is modified. For current and up-to-date information, we suggest that you consult current text or web references.