THE 12TH EDITION of the AAIDD DIAGNOSTIC AND TERMINOLOGY MANUAL

BY ROBERT L. SCHALOCK, RUTH LUCKASSON AND MARC J. TASSE

The scientific definition of the term intellectual disability (ID) is relevant to the lives of people with ID and their families in very important ways – think personal identity and accessing needed services and supports such as early intervention, IEP, waiver services, Medicaid insurance, and Social Security Disability benefits. Think also about media and communication, and risk of stigma

Title: Intellectual Disability: Definition, Diagnosis, Classification, and Systems of Supports (12th Ed.)

Authors: Robert L. Schalock, Ruth Luckasson and Marc J. Tasse

Publisher: American Association on Intellectual and Developmental Disabilities

Publication Date: January 2021 Hardcover: 280 pages ISBN-13: 978-0-9983983-6-5 Available at: aaidd.org and amazon.com

This year, the premier professional organization in the field of ID published the updated definition of ID. This event occurs only about every 10 years (beginning in 1921), so it is worth paying attention to the 12th edition. In this article, we provide a summary of the updated definition of ID and other important aspects of the American Association on Intellectual and Developmental Disabilities (AAIDD) manual. 

To begin, the purposes of a definition of intellectual disability are to explain precisely the term, establish the meaning and boundaries of the term, and separate who is included within the term from those who are outside the term. Significant consequences can result from the way a term is defined. A definition can make someone eligible or ineligible for supports and services, subjected to something or not subjected to it (e.g., involuntary commitment), exempted from something or not exempted (e.g., from the death penalty), included or not included (as to protections against discrimination and equal opportunity), and/or entitled or not entitled (e.g., certain Social Security benefits or other financial benefits).

The definition of intellectual disability found in the 12th edition of the AAIDD manual (Schalock, Luckasson, & Tassé, 2021) is that intellectual disability is characterized by significant limitations both in intellectual functioning and in adaptive behavior as expressed in conceptual, social, and practical adaptive skills. This disability is manifest during the developmental period, which is defined operationally as before the individual attains age 22. 

Assumptions are an essential part of the definition of intellectual disability because they clarify the context from which the definition arises and indicate how the definition should be applied. Thus, the definition cannot stand alone. The following assumptions are essential to the definition's implementation:

1. Limitations in present functioning must be considered within the context of community environments typical of the individual's age peers and culture.

2. Valid assessment considers cultural and linguistic diversity as well as differences in communication, sensory, motor, and behavioral factors.

3. Within an individual, limitations often coexist with strengths.

4. An important purpose of describing limitations is to help inform the development of a profile of needed supports.

5. With appropriate personalized supports over a sustained period, the life functioning of the person with intellectual disability generally will improve.

These five assumptions demonstrate, front and center on page 1 of the manual, important values about community living, authentic assessment, the presence of strengths and limitations shown by every person, the purpose for describing the individual's limitations, and the fact that improved life functioning will result if the individual is provided needed supports. The assumptions also reflect the distinction between the diagnosis of intellectual disability, which involves significant limitations both in intellectual functioning and adaptive behavior, and age of onset during the developmental period, and the expression of intellectual disability, which involves the reciprocal engagement among human functioning dimensions, systems of supports, and human functioning outcomes.

An important feature of the 12th edition of the AAIDD manual is the inclusion of practice guidelines regarding the diagnosis, classification, and planning supports for people with intellectual disability. The basis of these practice guidelines is current research, expert opinion, and peer-reviewed publications The purposes of the practice guidelines are to: (a) facilitate best practices regarding the diagnosis, classification, and planning supports for people with intellectual disability: (b) provide an integrated approach to disability policy development, implementation, and evaluation; (c) suggest a holistic framework for ID-related research; (d) connect valued foundational concepts to valued policy; and (e) enhance the functioning and well-being of people with intellectual disability. In providing this overview of the 12th edition of the AAIDD manual, we hope that the above information facilitates a better understanding of how important a scientific definition is and clarifying current best practices regarding defining, diagnosing, classifying, and planning and implementing individualized supports for people with ID. People with ID and their families are essential partners in understanding ID and the assumptions; collaborating in best practice procedures for its diagnosis, optional subgroup classification, and development and implementation of individualized systems of supports; and building strong relationships with clinicians. Facilitating this process is one of the major goals of the 12th edition of the AAIDD manual.•

ABOUT THE AUTHORS:

Robert L. Schalock, Ph.D. is (Corresponding Author) is Professor Emeritus, Hastings College (Nebraska). Ruth Luckasson, JD. Is Distinguished Professor, Chair, Department of Special Education, University of New Mexico. Marc J. Tasse, Ph.D. is Director, Nisonger Center-UCEDD, Professor, Departments of Psychology and Psychology, The Ohio State University.

PROPER DEFINITION : PRACTICE GUIDELINES FOR DIAGNOSIS, CLASSIFICATION AND SYSTEMS OF SUPPORTS

Individuals with ID and their families, as core members of the teams that assess for eligibility, design for supported functioning, and monitor for quality of supports, may be especially interested in the practice guidelines listed below. Interactions with clinicians will be enhanced if all members of the team share an understanding of the guidelines for diagnosis, classification and planning supports. These practice guidelines are listed below:

PRACTICE GUIDELINES REGARDING THE DIAGNOSIS OF INTELLECTUAL DISABILITY:

1. A diagnosis of intellectual disability requires significant limitations in intellectual functioning and adaptive behavior, and origination during the developmental period, which is defined operationally as before the individual attains age 22.

2.Assessment instruments used to formulate a diagnosis of intellectual disability should use reliable, valid, individually administered, comprehensive, and standardized tests that yield (a) a full-scale IQ score (for the intellectual functioning criterion), and (b) a standardized adaptive behavior measure that assesses the following three adaptive behavior domains: conceptual, social, and practical.

3.Equal weight and joint consideration are given to intellectual functioning and adaptive behavior in making a diagnosis of intellectual disability.

PRACTICE GUIDELINES REGARDING CLASSIFICATION IN THE FIELD OF INTELLECTUAL DISABILITY:

1. Classification is an optional post diagnosis organizing scheme that uses an explicit framework and a systematic process to subdivide the group of individuals with intellectual disability into smaller groups.

2. The preferred subgroup classification scheme is based on the intensity of support needs. Other potential purposes of subgroup classification are to describe the extent of limitations in conceptual, social, and practical adaptive skills, or to describe the extent of limitations in intellectual functioning.

3. Any subgroup classification should serve an important purpose, have benefit to the person, be based on relevant information, and provide a better understanding of the person.

4. Best practices in subgroup classification reject stigmatizing subgroup classification terms. The selected terminology should demonstrate respect for the person, promote accuracy, and enhance understanding.

PRACTICE GUIDELINES REGARDING SYSTEMS OF SUPPORTS:

1. The assessment of the pattern and intensity of an individual's support needs should be based on a professional evaluation, including use of an individually administered standardized support needs scale.

2. Systems of support should be built on values and support relationships and should incorporate choice and personal autonomy, inclusive environments, generic supports, and specialized supports.

3. Systems of support should be person centered, comprehensive, coordinated, and outcome oriented.

4.The provision of supports should be coordinated through a personal support plan that (a) is developed, implemented, reviewed, and evaluated by a support team of which the person with intellectual disability is a member, and (b) aligns personal goals and support needs with specific support strategies with desired personal outcomes.