What is iq for intellectual disability?
IQ test results fall along the normal (bell-shaped) curve, with an average IQ of 100, and individuals who are intellectually disabled are usually two standard deviations below the average (IQ below 70).
Intelligence is the general mental capacity that involves reasoning, planning, solving problems, thinking abstractly, comprehending complex ideas, learning efficiently, and learning from experience (AAIDD, 2010). Historically, intellectual disability (previously termed “mental retardation”) has been defined by significant cognitive deficits—which has been established through a standardized measure of intelligence, in particular, with an IQ score of below 70 (two standard deviations below the mean of 100 in the population)—and also by significant deficits in functional and adaptive skills. Adaptive skills involve the ability to carry out age-appropriate daily life activities. Two different systems for classifying intellectual disability (ID) used in the United States are that of the American Association on Intellectual and Developmental Disabilities (AAIDD) and the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5), which is published by the American Psychiatric Association. Both of these systems classify severity of ID according to the levels of support needed to achieve an individual's optimal personal functioning (see Table 9-1).
DSM-5 defines intellectual disabilities as neurodevelopmental disorders that begin in childhood and are characterized by intellectual difficulties as well as difficulties in conceptual, social, and practical areas of living. The DSM-5 diagnosis of ID requires the satisfaction of three criteria:
The DSM-5 definition of ID encourages a more comprehensive view of the individual than was true under the fourth edition, DSM-IV. The DSM-IV definition included impairments of general mental abilities that affect how a person functions in conceptual, social, and daily life areas. DSM-5 abandoned specific IQ scores as a diagnostic criterion, although it retained the general notion of functioning two or more standard deviations below the general population. DSM-5 has placed more emphasis on adaptive functioning and the performance of usual life skills. In contrast to DSM-IV, which stipulated impairments in two or more skill areas, the DSM-5 criteria point to impairment in one or more superordinate skill domains (e.g., conceptual, social, practical) (Papazoglou et al., 2014).
