Surprisingly, the term “intellectual disability” is not defined by the DD Act.
The definition that is often referred to when doing a search for “intellectual disability”, comes from the American Association on Intellectual and Developmental Disabilities (AAIDD):
Definition of Intellectual Disability
Intellectual disability is a disability characterized by significant limitations in both intellectual functioning and in adaptive behavior, which covers many everyday social and practical skills. This disability originates before the age of 18.
Intellectual functioning—also called intelligence—refers to general mental capacity, such as learning, reasoning, problem solving, and so on.
One way to measure intellectual functioning is an IQ test. Generally, an IQ test score of around 70 or as high as 75 indicates a limitation in intellectual functioning.
Adaptive behavior is the collection of conceptional, social, and practical skills that are learned and performed by people in their everyday lives.
- Conceptual skills—language and literacy; money, time, and number concepts; and self-direction.
- Social skills—interpersonal skills, social responsibility, self-esteem, gullibility, naïveté (i.e., wariness), social problem solving, and the ability to follow rules/obey laws and to avoid being victimized.
- Practical skills—activities of daily living (personal care), occupational skills, healthcare, travel/transportation, schedules/routines, safety, use of money, use of the telephone.
Age of Onset
This condition is one of several developmental disabilities—that is, there is evidence of the disability during the developmental period, which in the US is operationalized as before the age of 18.
But in defining and assessing intellectual disability, the AAIDD stresses that additional factors must be taken into account, such as the community environment typical of the individual’s peers and culture. Professionals should also consider linguistic diversity and cultural differences in the way people communicate, move, and behave.
Finally, assessments must also assume that limitations in individuals often coexist with strengths, and that a person’s level of life functioning will improve if appropriate personalized supports are provided over a sustained period.
Only onthe basis of such many-sided evaluations can professionals determine whether an individual has intellectual disability and tailor individualized support plans.
This is additional information from the AIDD, “Frequently Asked Questions on Intellectual Disability”:
Is intellectual disability the same as mental retardation? Why do some programs and regulations still say mental retardation?
The term intellectual disability covers the same population of individuals who were diagnosed previously with mental retardation in number, kind, level, type, duration of disability, and the need of people with this disability for individualized services and supports.
Furthermore, every individual who is or was eligible for a diagnosis of mental retardation is eligible for a diagnosis of intellectual disability.
While intellectual disability is the preferred term, it takes time for language that is used in legislation, regulation, and even for the names of organizations, to change.
Is intellectual disability the same as developmental disabilities?
"Developmental Disabilities" is an umbrella term that includes intellectual disability but also includes other disabilities that are apparent during childhood. Developmental disabilities are severe chronic disabilities that can be cognitive or physical or both. The disabilities appear before the age of 22 and are likely to be lifelong.Some developmental disabilities are largely physical issues, such as cerebral palsy or epilepsy. Some individuals may have a condition that includes a physical and intellectual disability, for example Down syndrome or fetal alcohol syndrome. Intellectual disability encompasses the “cognitive” part of this definition, that is, a disability that is broadly related to thought processes. Because intellectual and other developmental disabilities often co-occur, intellectual disability professionals often work with people who have both types of disabilities.