The American Association on Intellectual and Developmental Disabilities (AAIDD) Diagnostic Criteria for Intellectual Disability

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The American Association on Intellectual and Developmental Disabilities (formerly AAMR) was founded in 1876 by Edouard Seguin, M.D. It is the world's oldest, trans-disciplinary, professional organization devoted to intellectual disability (ID, formerly mental retardation). Headquartered in Washington, DC, the AAIDD has many purposes:

  • researching intellectual disabilities;
  • increasing social awareness;
  • promoting progressive governmental policy;
  • supporting families;
  • developing rehabilitative strategies for persons with intellectual and developmental disabilities.

The AAIDD has refined and modified ID diagnostic criteria since 1921. The criteria are updated based on new research and changes in clinical practices.


The AAIDD definition and APA definition are quite similar. The three primary criteria remain the same although the labels are slightly different:

1. AAIDD also uses limitations in intellectual functioning. Like the APA criteria, this refers to mental abilities. Some examples are learning, reasoning, and problem solving. One criterion 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. These scores would occur about 2.5% of the population. Or stated differently, 97.5% of people of the same age and culture would score higher. The tests used to measure IQ must be standardized and culturally appropriate.

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2. AAIDD labels adaptive functioning as adaptive behavior. Standardized tests also determine limitations. Adaptive behavior comprises three skill types.

  • Conceptual skills: This includes language and literacy; mathematics; time and number concepts; and self-direction.
  • Social skills: This includes interpersonal skills; social responsibility; self-esteem; gullibility; social problem solving; and the ability to follow rules/obey laws. It also includes naïveté. This lack of wariness leads to victimization.
  • Practical skills: This includes activities of daily living (personal care). It also includes occupational skills, healthcare, travel/transportation, schedules/routines, safety, use of money, use of the telephone.

Limitations in adaptive behavior are indicated in one of two ways. One possibility is a score approximately two standard deviations below average in any one of the three areas. The second possibility is an overall score in all three areas is approximately two standard deviations below the average score for that age group.

3. This disability originates before the age of 18.

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