INTRODUCTION — Intellectual disability (ID) is a static encephalopathy with multiple etiologies that encompasses a broad spectrum of functioning, disability, and strengths. The term is synonymous with and is now preferred over the older term, mental retardation. The term global developmental delay is usually used to describe children younger than age five with significant cognitive deficits, because intelligence quotient (IQ) testing is less reliable in this age group; the cognitive deficits may be accompanied by other developmental deficits as well. A variety of other terms are used outside of the United States to describe intellectual disability (table 1). ID 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 educational resources. The definition, epidemiology, causes, clinical presentation, and diagnosis of intellectual disability will be presented here. Evaluation, management, outcomes, and prevention of ID are discussed separately. (See "Intellectual disability (mental retardation) in children: Evaluation" and "Intellectual disability (mental retardation) in children: Management; outcomes; and prevention".) DEFINITIONS — Intellectual disability (ID) is a state of functioning that typically begins in childhood and is characterized by limitations in intelligence and adaptive skills [1]. Two definitions are commonly used. One is published by the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, text revision (DSM–IV) and the other by the American Association on Intellectual and Developmental Disabilities (AAIDD). DSM-IV definition — DSM-IV uses the term mental retardation instead of intellectual disability, which it defines by three co-existing criteria [2]: Significant sub-average intellectual function Significant limitations in adaptive functioning Onset before 18 years of age The severity of cognitive impairment is characterized by the extent of deviation of the IQ below 100, the estimated mean for the population. The lower limit of normal is considered to be two standard deviations below the mean or an IQ of 70. Gradations of severity include IQs in the following ranges [2]: Mild – from between 50 and 55 to approximately 70 Moderate – from between 35 and 40 to between 50 and 55 Severe – from between 20 and 25 to between 35 and 40 Profound – from
Posted on: Sun, 25 Aug 2013 10:46:29 +0000
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