*Please note that the information is this FAQ is not meant to substitute for a reading of the text, Mental Retardation: Definition, Classification and Systems of Support (Luckasson et al., 2002). A thorough and responsible understanding of the AAIDD definition system of diagnosing and classifying intellectual disability in an individual can only be obtained by reading the text in its entirety. This FAQ is just meant to provide a very general overview of the AAIDD definition system.*
Intellectual disability is a disability characterized by significant limitations both in intellectual functioning and in adaptive behavior as expressed in conceptual, social, and practical adaptive skills. This disability originates before the age of 18.
Intellectual disability is the currently preferred term for the disability historically referred to as mental retardation. Although the preferred name is intellectual disability, the authoritative definition and assumptions promulgated by the American Association on Intellectual and Developmental Disabilities (AAIDD and previously, AAMR) remain the same as those found in the Mental Retardation: Definition, Classification and Systems of Supports manual (Luckasson et al., 2002).
The term intellectual disability covers the same population of individuals who were diagnosed previously with mental retardation in number, kind, level, type, and duration of the 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.
All persons who are working in this field should read an extended discussion of the renaming of mental retardation and understanding the change to the term intellectual disability. This extended discussion is found in the following article written by the AAIDD Terminology and Classification Committee: Schalock, R. L. et al. (2007, April). The renaming of mental retardation: Understanding the change to the term intellectual disability. Intellectual and Developmental Disabilities, 45 (2), pp. 116-124.
When using the AAIDD definition, classification, and systems of supports, professionals and other team members must:
A disability refers to personal limitations that are of substantial disadvantage to the individual when attempting to function in society. A disability should be considered within the context of the individual’s environmental and personal factors, and the need for individualized supports.
Intelligence refers to a general mental capability. It involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly, and learn from experience. Although not perfect, intelligence is represented by Intelligent Quotient (IQ) scores obtained from standardized tests given by a trained professional.
With regards to the intellectual criterion for the diagnosis of intellectual disability, limitations in intellectual functioning are generally thought to be present if an individual has an IQ test score of approximately 70 or below. IQ scores must always be considered in light of the standard error of measurement, appropriateness, and consistency with administration guidelines. Since the standard error of measurement for most IQ tests is approximately 5, the ceiling may go up to 75. This represents a score approximately 2 standard deviations below the mean, considering the standard error of measurement. It is important to remember, however, that an IQ score is only one criterion: Significant limitations in adaptive behavior skills and evidence that the disability was present before age 18 are two additional criteria in determining if a person has intellectual disability.
Adaptive behavior represents the conceptual, social, and practical skills that people have learned to be able to function in their everyday lives. Significant limitations in adaptive behavior impact a person's daily life and affect the ability to respond to a particular situation or to the environment.
Limitations in adaptive behavior can be determined by using standardized tests. On these standardized measures, significant limitations in adaptive behavior are operationally defined as performance that is at least 2 standard deviations below the mean of either (a) one of the following three types of adaptive behavior: conceptual, social, or practical, or (b) an overall score on a standardized measure of conceptual, social, and practical skills.
Receptive and expressive language
Reading and writing
Gullibility (likelihood of being tricked or manipulated)
Personal activities of daily living such as eating, dressing, mobility and toileting. Instrumental activities of
daily living such as preparing meals, taking medication, using the telephone, managing money, using
transportation, and doing housekeeping activities.
Maintaining a safe environment
Supports are resources and strategies necessary to promote the development, education, interests, and personal well being of a person with intellectual disability. Supports can be provided by a parent, friend, teacher, psychologist, doctor, or by any appropriate person or agency.
The concept of supports originated about 15 years ago and has revolutionized the way habilitation and education services are provided to persons with intellectual disability. Rather than mold individuals into preexisting diagnostic categories and force them into existing models of service, the supports approach evaluates the specific needs of the individual and then suggests strategies and services to optimize individual functioning. The supports approach also recognizes that individual needs and circumstances will change over time.
Supports were an innovative aspect of the 1992 AAIDD manual and they remain critical in the 2002 system. In 2002, they have been dramatically expanded and improved to reflect significant progress over the last decade.
Providing individualized supports can improve personal functioning, promote self-determination, and enhance the well being of a person with intellectual disability. Supports also leads to community inclusion of persons with intellectual disabilities. Focusing on supports as the way to improve education, employment, recreation, and living environments is an important part of a person-centered approach to providing care to people with intellectual disability.
AAIDD recommends that an individual's need for supports be analyzed in at least nine key areas such as human development, teaching and education, home living, community living, employment, health and safety, behavior, social, and protection and advocacy.
Human Development Activities
Teaching and Education Activities
Home Living Activities
Community Living Activities
Participating in recreation and leisure activities
Going to visit friends and family
Shopping and purchasing goods
Interacting with community members
Using public buildings and settings
Health and Safety Activities
Protection and Advocacy Activities
The causes of intellectual disability can be divided into biomedical, social, behavioral, and educational risk factors that interact during the life of an individual and/or across generations from parent to child. Biomedical factors are related to biologic processes, such as genetic disorders or nutrition. Social factors are related to social and family interaction, such as child stimulation and adult responsiveness. Behavioral factors are related to harmful behaviors, such as maternal substance abuse. Educational factors are related to the availability of family and educational supports that promote mental development and increases in adaptive skills. Also, factors present during one generation can influence the outcomes of the next generation. By understanding inter-generational causes, appropriate supports can be used to prevent and reverse the effects of risk factors.
Founded in 1876, AAIDD is the world's oldest and largest interdisciplinary organization of professionals concerned about mental retardation and related developmental disabilities. With headquarters in Washington, DC, AAIDD has a constituency of more than 50,000 people and an active core membership of over 3,500 in the United States and in 55 other countries. The mission of AAIDD is to promote progressive policies, sound research, effective practices, and universal rights for people with intellectual disabilities.
AAIDD has updated the definition of mental retardation ten times since 1908, based on new information, changes in clinical practice, or breakthroughs in scientific research. The 10th edition of Mental Retardation: Definition, Classification, and Systems of Supports (2002) contains a comprehensive update to the landmark 1992 definition and provides important new information, tools, and strategies for the field and for anyone concerned about people with intellectual disability.
AAIDD anticipates publishing the next classification manual in 2010/2011.
AAIDD applauds and fully supports the U.S. Supreme Court decision to stop executing persons with intellectual disability. AAIDD has always advocated against the death penalty of people with intellectual disabilities and has long served as amicus curiae in Supreme Court cases. In 2001, AAIDD and eight other disability organizations presented an amicus brief to the U.S. Supreme Court advocating against the death penalty in the Atkins case.
James W. Ellis, past president of AAIDD, who also argued the case for Atkins says, “The Court has recognized the consensus among the American people, even those who support the death penalty. They are deeply disturbed by the prospect that people with intellectual disability/mental retardation could face execution.”
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