Kaplan + Sadock's Synopsis of Psychiatry, 11e

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31.3 Intellectual Disability

intellectual disability and were instrumental in advocating for Public Law 94–142. The American Association on Intellectual and Developmental Disabilities, formerly known as The Ameri- can Association on Intellectual disability (AAMR), is the most prominent advocacy organization in this field. It has been very influential in educating the public about, and in supporting research and legislation relating to, intellectual disability. The AAIDD promotes a view of intellectual disability as a functional interaction between an individual and the environ- ment, rather than a static designation of a person’s limitations. Within this conceptual framework, a child or adolescent with intellectual disability is determined to need intermittent, limited, extensive, or pervasive “environmental support” with respect to a specific set of adaptive function domains. These include communication, self-care, home living, social or interpersonal skills, use of community resources, self-direction, functional academic skills, work, leisure, health, and safety. The United Nations Convention on the Rights of Persons with Disabilities (2006) has created a forum to promote the full social inclusion of people with intellectual disability. Through its recognition and focus on social barriers, this international forum aims to provide protections for individuals with intellec- tual disability, and to seek more inclusion of those with intellec- tual disability in social, civic, and educational activities. Nomenclature The accurate definition of intellectual disability has been a chal- lenge for clinicians over the centuries. All current classification systems underscore that intellectual disability is based on more than cognitive deficits, that is, it also includes impaired social adaptive function. According to DSM-5, a diagnosis of intel- lectual disability should be made only when there are deficits in intellectual functioning and deficits in adaptive functioning (Table 31.3-1). Once intellectual disability is recognized, the level of severity is determined by the level of adaptive func- tional impairment. Classification DSM-5 criteria for intellectual disability include significantly subaverage general intellectual functioning associated with concurrent impairment in adaptive behavior, manifested before the age of 18. The diagnosis is made independent of coexisting physical or mental disorders. Table 31.3-2 presents an overview of developmental levels in communication, academic func- tioning, and vocational skills expected of persons with various degrees of intellectual disability. If the clinician chooses to use a standardized test of intelli- gence—which is still common practice—the term significantly subaverage is defined as an IQ of approximately 70 or below or two standard deviations below the mean for the particular test. Adaptive functioning can be measured by using a standard- ized scale, such as the Vineland Adaptive Behavior Scale. This scale scores communications, daily living skills, socialization, and motor skills (up to 4 years, 11 months) and generates an adaptive behavior composite that is correlated with the expected skills at a given age. Approximately 85 percent of individuals who have intel- lectual disability fall within the DSM-5 mild intellectual

functioning (reasoning, learning, and problem solving) and in adaptive behavior (conceptual, social, and practical skills) that emerges before the age of 18 years. Wide acceptance of this definition has led to the international consensus that an assess- ment of both social adaptation and intelligence quotient (IQ) are necessary to determine the level of intellectual disability. Mea- sures of adaptive function assess competency in social func- tioning, understanding of societal norms, and performance of everyday tasks, whereas measures of intellectual function focus on cognitive abilities. Although individuals with a given intel- lectual level do not all have identical levels of adaptive func- tion, epidemiologic data suggest that prevalence of intellectual disability is largely determined by intellectual level and a level of adaptive function, which typically corresponds closely with cognitive ability. In the Diagnostic and Statistical Manual of Mental Dis- orders, Fifth Edition (DSM-5), various levels of severity of intellectual disability are determined on the basis of adaptive functioning, not on IQ scores. This change in emphasis from prior diagnostic manuals has been adopted by DSM-5 because adaptive functioning determines the level of support that is required. Furthermore, IQ scores are less valid in the lower por- tions of the IQ range. Making a determination of severity level of intellectual disability, according to DSM-5, includes assess- ment of functioning in a conceptual domain (e.g., academic skills), a social domain (e.g., relationships), and a practical domain (e.g., personal hygiene). Societal approaches to children with intellectual disability have shifted significantly over time. Historically, in the mid- 1800s many children with intellectual disability were placed in residential educational facilities based on the belief that with sufficient intensive training, these children would be able to return to their families and function in society at a higher level. However, the expectation of educating these children in order to overcome their disabilities was not realized. Gradually, many residential programs increased in size, and eventually the focus began to shift from intensive education to more custodial care. Residential settings for children with intellectual disabil- ity received their maximal use in the mid-1900s, until public awareness of the crowded, unsanitary, and, in some cases, abu- sive conditions sparked the movement toward “deinstitution- alization.” An important force in the deinstitutionalization of children with intellectual disability was the philosophy of “nor- malization” in living situations, and “inclusion” in educational settings. Since the late 1960s, few children with intellectual disability have been placed in residences, and the concepts of normalization and inclusion remain prominent among advocacy groups and parents. The passage of Public Law 94–142 (the Education for all Handicapped Children Act) in 1975 mandates that the public school system provide appropriate educational service to all children with disabilities. The Individuals with Disabilities Act in 1990 extended and modified the above legislation. Currently, provision of public education for all children, including those with disabilities, “within the least restrictive environment” is mandated by law. In addition to the educational system, advocacy groups, including the Council for Exceptional Children (CEC) and the National Association for Retarded Citizens (NARC) are well known parental lobbying organizations for children with