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Intellectual disability in children: Definition, diagnosis, and assessment of needs

Penelope Pivalizza, MD
Seema R Lalani, MD
Section Editors
Marc C Patterson, MD, FRACP
Helen V Firth, DM, FRCP, DCH
Carolyn Bridgemohan, MD
Deputy Editor
Carrie Armsby, MD, MPH


Intellectual disability (ID) is a neurodevelopmental disorder characterized by deficits in intellectual and adaptive functioning that present before 18 years of age [1]. ID is heterogeneous in etiology and encompasses a broad spectrum of functioning, disability, needs, and strengths.ID affects approximately 1 percent of the population. It is an important public health issue because of its prevalence and the need for extensive support services. Its management requires early diagnosis and intervention, coupled with access to health care and appropriate supports.

The definition and diagnosis of ID, including assessment of needs for support, are reviewed here. Other aspects of ID are discussed separately:

(See "Intellectual disability in children: Evaluation for a cause".)

(See "Intellectual disability in children: Management, outcomes, and prevention".)


Intellectual disability — ID is a state of functioning that begins in childhood and is characterized by limitations in intelligence and adaptive skills. The term replaces and improves upon the older term of "mental retardation" [2]. A variety of other terms are used outside of the United States to describe ID (table 1).

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Literature review current through: Nov 2017. | This topic last updated: Aug 15, 2016.
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