Abstract

The World Health Organization (WHO) is in the process of seeking input from professional stakeholder groups and consumers regarding the draft proposals of the 11th edition of the International Classification of Diseases (ICD–11). The American Association on Intellectual and Developmental Disabilities (AAIDD) convened a small group of distinguished interdisciplinary expert professionals in intellectual disability to review the ICD–11 proposal regarding revisions of the condition previously known as “mental retardation.” This article presents the recommendations made by the AAIDD to the WHO Secretariat regarding the name, definition, diagnostic guidelines, and classification of the condition known today as intellectual disability.

AAIDD Proposed Recommendations for ICD–11 and the Condition Previously Known as Mental Retardation

The American Association on Intellectual and Developmental Disabilities (AAIDD) was founded in 1876 and is the oldest interdisciplinary professional society with a focus on intellectual disability in the world. Since its inception, AAIDD has produced guidelines naming, defining, and diagnosing the condition known today as “intellectual disability.” The first official AAIDD definition and classification manual on intellectual disability was published in 1910 (Committee on Classification of the Feebleminded, 1910) and was the first professional definition that proposed an international terminology and classification system for intellectual disability. AAIDD has revised its definition and diagnostic criteria as the science and understanding of the condition has evolved over time. The 11th edition of AAIDD's Intellectual Disability: Definition, Classification, and Systems of Support was published in 2010 (Schalock et al., 2010).

World Health Organization

The World Health Organization (WHO) was founded in 1948 as a global organization of the United Nations. Its mission includes providing world-wide leadership on health matters, establishing norms and standards, articulating evidence-based policies, providing technical support to countries, and monitoring and assessing health trends around the globe. A core component of the WHO constitution, ratified by all 193 current WHO member countries, includes establishing and revising international classifications on health so that there is a consensual, meaningful, and useful system that governments, health practitioners, and consumers can use as a common language (Madden, Sykes, & Ustun, 2013). When it was established in 1948, the WHO assumed the publication of the sixth revision of the International Classification of Diseases (ICD).

ICD

The ICD is a classification system of all health conditions (more than 10,000 disease and disorder codes, including “mental retardation”) and has a world-wide dissemination and use. The ICD is revised approximately every 10 years to incorporate changes in the health field. The ICD is currently in its 10th revision (ICD–10; World Health Organization, 1992).

The World Health Assembly, consisting of the ministers/secretaries of health of all WHO member countries, directed the WHO to revise the ICD–10, and its publication is expected in 2015 (International Advisory Group, 2011). There are six official languages of the WHO and hence, when the ICD–11 is completed, it will be simultaneously released in all six official languages: Arabic, Chinese, English, French, Russian, and Spanish.

The WHO Department of Mental Health and Substance Abuse oversees the revision of the ICD–10 Chapter V, which includes the classification of Mental and Behavioral Disorders. It is within this grouping that “mental retardation” is listed. The five main uses of the Mental and Behavioral Disorders classification are: (1) clinical, (2) research, (3) teaching and training, (4) health statistics, and (5) public health (International Advisory Group, 2011).

Steps Remaining in the Development of the ICD–11

The process of developing the ICD–11 is monumental, as experts are called to accurately identify and describe more than 10,000 conditions. For the condition formerly known as “mental retardation” the process includes the following:

  1. The international and interdisciplinary professional expert members of the Working Group assigned to revise the ICD–10 classification “mental retardation” (see Salvador-Carulla et al., 2011) present their proposed changes to the WHO Secretariat.

  2. The WHO Secretariat, in consultation with the International Advisory Group for the Revision of the ICD–10 Mental and Behavioral Disorders, reviews the proposal and prepares it for public review and comment.

  3. The WHO encourages consultation with and input from stakeholders. These stakeholders include the 193 WHO member-country governments, multidisciplinary health professionals, and consumers of health services and their families (International Advisory Group, 2011).

  4. Revisions are made to the proposal.

  5. Online and in vivo clinical field testing of the proposal is performed.

  6. Finalization of the category for inclusion in the ICD–11 (anticipated May 2015).

The first two steps above have been completed and the draft proposals for the ICD–11 are publically available on the WHO Web site. As part of the process to provide consultation and input, AAIDD convened a meeting of North American experts to review and provide feedback on the current diagnostic proposal for the condition formerly known as “mental retardation.”

AAIDD Convened a Group of Recognized Experts

AAIDD convened a small but diverse group of recognized experts from the field of intellectual disability in Washington, DC for a 1 and 1/2-day meeting (January 11–12, 2012). This group of US and Canadian intellectual disability experts and stakeholders reviewed the current diagnostic proposal submitted for the ICD–11 Working Group on the Classification of Intellectual Disabilities and discussed three important aspects regarding the condition previously known as mental retardation: (1) the current consensus regarding terminology, (2) the current consensus regarding the diagnostic criteria, and (3) field testing of the ICD–11.

The proposed ICD–11 Content Form for Mental and Behavioral Disorders, submitted by the Working Group, served as a useful mechanism to operationalize the recommendations of the North American intellectual disability experts and stakeholders. Proposed revisions of the ICD–11 Content Forms for Mental and Behavioral Disorders that convey AAIDD's recommendations for terminology and classification, using the ICD taxonomy, for consideration by the WHO were submitted with narrative comments. Below is a summary of AAIDD's recommendations regarding the (1) terminology, (2) diagnostic criteria and classification, and (3) field testing of the ICD–11.

Recommendations

  • 1. Terminology: We recommend that the category name “Disorders of Intellectual Disability” (Disorders of ID) be used rather than “Intellectual Developmental Disorders.

RATIONALE: The term to replace “mental retardation” that has garnered the greatest international consensus is “intellectual disability.” With the understanding that the ICD–11 is a classification system of diseases and disorders, we recommend using “Disorders” but placing it before the most commonly used term, “intellectual disability.” This category name would retain the taxonomy of the ICD while using the term that has replaced “mental retardation” internationally.

We have three notable objections to the proposed “Intellectual Developmental Disorders” term. First, “Intellectual Developmental Disorders” is an entirely novel term, contrary to current usage, and presents no apparent intuitive advantage. Maintaining a consistent terminology is crucial in ensuring fairness, accuracy, and consistency in and across countries in critical areas including clinical practice, teaching/training, research, population-based statistics reporting, and public health services. Second, the use of “developmental” in the proposed name of the condition is redundant and unnecessary as (a) it is organized under the parent category of “Neurodevelopmental Disorders” and (b) there is a diagnostic criterion that specifies the need for the disorder to originate during the developmental period. Further, it is important to note that Disorders of Intellectual Disability are life-long and as such, diagnosis is made and re-affirmed in adults of all ages. Therefore, having “developmental” in the disorder's name would not contribute to any added specificity and would lead to confusion and added stigma when diagnosing older adults. Third, any diversity in terminology would most foreseeably lead to direct harm to individuals previously diagnosed with “mental retardation” in educational, service, and judicial settings.

Not only has the term “intellectual disability” become the most common internationally used term to refer to the condition previously named “mental retardation,” it has been almost universally adopted in the United States. In October 2010, President Barack Obama signed “Rosa's Law,” which replaced the term “mental retardation” with “intellectual disability” in all federal education, health, and labor laws. This year, we expect to see additional legislative and regulatory changes to replace remaining federal references to “mental retardation” with “intellectual disability.”

  • 2. Definition, Diagnostic Guidelines, and Classification

    We recommend the following definition, diagnostic guidelines, and children or constituent categories.

  • A. Definition. We recommend that the following be used as the definition of this condition:

A disorder of intellectual disability is a condition characterized by significant limitations in intellectual functioning and adaptive behaviour, originating during the developmental period.

RATIONALE. This simplified language outlines the three essential elements in a clearer and more concise manner.

  • B. Diagnostic Guidelines. We recommend that the following be used as the diagnostic guidelines for this condition:

There are three requirements for a diagnosis of Disorders of ID: (1) the presence of significant limitations in intellectual functioning; (2) the presence of significant limitations in adaptive behavior; and (3) onset during the developmental period. In the context of ICD–11, intelligence is not considered a unitary characteristic but rather an umbrella term that includes reasoning, planning, solving problems, thinking abstractly, comprehending complex ideas, learning quickly, and learning from experience that is age-appropriate, community-based, and meets the standards for culturally appropriate demands of daily life.

RATIONALE: This simplified language conveys the commonly understood diagnostic criteria for the condition and further clarifies the criteria by eliminating one proposed criterion, “limitations or difficulties in learning.” As “learning” is by definition an adaptive behaviour rather than a unique diagnostic element, evidence of this characteristic is most properly subsumed under the broader criterion of “the presence of significant limitations of adaptive behavior.”

Historically, there has been substantive consistency among the WHO, AAIDD, and the American Psychiatric Association's (APA) definition and diagnostic criteria of “intellectual disability” (formerly known as “mental retardation”). We are pleased to note that the next iteration of APA's Diagnostic and Statistical Manual (DSM) will be consistent in terminology and diagnostic criteria with those promulgated by AAIDD. The use of different terms and diagnostic guidelines in the authoritative classification manuals (ICD, AAIDD, DSM) for “intellectual disability” would create havoc in government agencies, the health and education systems, and for individuals with intellectual disability and their families. In particular, government policy making, service eligibility determination, research communication, and reporting of public health statistics would be substantially disrupted should the WHO promulgate a definition and diagnostic guidelines of Disorders of Intellectual Disability that are different from the current scientific consensus.

  • C. “Children” or Constituent Categories: We recommend that the “Children” or Constituent Categories be identified as follows:

Disorder of Intellectual Disability, Marked

Disorder of Intellectual Disability, Extensive

Disorder of Intellectual Disability, Pervasive

Disorder of Intellectual Disability, Other

RATIONALE. This recommendation addresses both scientific understanding of the condition and taxonomy. First, we recommend combining the proposed “Severe” and “Profound” classifications into one category. There is no scientific rationale or psychometric validity to maintaining a 4-level classification system. Collapsing all individuals with IQ scores below 40 into one category is more scientifically and psychometrically supported than attempting to impose a classification cut-off that is five standard deviations below the population mean (i.e., IQ score  =  25). Existing standardized tests of intelligence cannot reliably or validly distinguish among individuals with IQ scores below 40. Hence, we propose a classification of Disorders of ID with three levels of severity.

Second, we recommend relating the levels of severity to a system that incorporates factors other than merely the person's level of intellectual functioning. Our rationale for changing the naming convention of the severity levels from the previously established labels of mild, moderate, severe, and profound is to avoid the incongruous association of “significant limitations” with a “mild” level of severity and to provide a more meaningful system of proposed constituent categories. A constituent category of a serious disorder that contains the label of “mild” is too often misconstrued to imply that the condition is less severe than it is. Hence, we propose adopting the following constituent categories that are less burdened with such connotation: Marked, Extensive, and Pervasive. We also propose retaining the “Other” category as a provisional diagnosis when a clinical subtype specification cannot be made due to age; the presence of sensory, physical, or behavioral difficulties; or in situations in which it is not possible to conduct a more detailed and valid assessment.

  • 3. Field testing of the ICD–11. AAIDD and its partner organizations have access to tens of thousands of mental health, health, and educational professionals as well as individuals with intellectual disability and their families who could contribute to the ICD–11 online and in vivo clinical field testing. AAIDD has a large number of members across North America and in more than 50 countries around the world and stands ready to assist the WHO in its field testing of this category.

Summary

Until the field of neuroscience is able to provide genetic markers or neurobiological phenotypes that accurately and reliably diagnose all cases of intellectual disability, the ICD will continue to rely on a clinical assessment of functional skills, such as intellectual functioning and adaptive behavior, to ensure clinical utility of the classification system. AAIDD strongly recommends a unifying effort across organizations and experts in ratifying a naming, defining, and classifying convention for the condition widely known as “intellectual disability.” This is especially true if the goal of the ICD is to efficiently identify people on a global level who have the greatest mental health needs and to ensure that they are appropriately identified whether it is for clinical, research, teaching/communication, statistical reporting, epidemiology, or other public health purposes.

AAIDD convened a small but diverse group of recognized experts from the field of intellectual disability from the United States and Canada to carefully review the proposed revisions of the Working Group on the condition previously known as “mental retardation”; in this document we presented a series of recommendations on the basis of the input from that group. The incorporation of these recommendations into the ICD–11 would ensure congruence among the ICD, DSM, and AAIDD terminology and classification manual regarding the terminology, definition, and diagnostic guidelines for the condition now known world-wide as “intellectual disability.”

On the basis of the feedback from our professional stakeholder group, AAIDD provided to the WHO Secretariat complete and edited versions of the ICD–11 Content Form for Mental and Behavioral Disorders with recommendations for changes to the Working Group's draft proposal, including Content Forms (available from the lead author of this article) for each of the constituent categories.

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Author notes

Authors:

Marc J. Tassé (e-mail: marc.tasse@osumc.edu), Director, The Ohio State University Nisonger Center–University Center for Excellence in Developmental Disabilities (UCEDD), 1581 Dodd Drive, Columbus, OH 43210; Ruth Luckasson, Educational Specialties Chair, Department of Educational Specialties, College of Education, University of New Mexico; Margaret Nygren, Executive Director/CEO, American Association on Intellectual and Developmental Disabilities, 501 Third Street, NW, Suite 200, Washington, DC 20001.

The comments and recommendations in this report have been endorsed by the Board of Directors of AAIDD. This text does not necessarily reflect the opinions of each individual professional who participated in the AAIDD expert group. This group of experts included (in alphabetical order): Marty Ford, JD; George S. Jesien, PhD; Ruth Luckasson, JD; Diane Morin, PhD; William E. Narrow, MD, MPH; Margaret Nygren, EdD; J. Gregory Olley, PhD; Geoffrey M. Reed, PhD (representing the World Health Organization); Marc J. Tassé, PhD; and Michael L. Wehmeyer, PhD.