What is the standard score for intellectual disability?
Intellectual Disability (ID) (also known as Intellectual Developmental Disorder, and previously Mental Retardation) is a disorder with onset during the developmental period that includes both intellectual and adaptive functioning deficits in 3 domains: (1) conceptual, (2) social, and (3) practical domains. Intellectual disability is a heterogeneous condition with many different etiologies. Two other diagnoses exist under the intellectual disability diagnostic category in the DSM-5: and . Show
EpidemiologyIntellectual disability has a population prevalence of approximately 1%, and varies by age. Prevalence for severe intellectual disability is approximately 0.6%. Males are more likely than females to be diagnosed with both mild and severe forms of intellectual disability. The History of 'Mental Retardation'Mental retardation was a diagnostic label that included the the categories of idiot, imbecile, and moron, based on early IQ testing data. All of these terms started as medical terms, and did not have the negative and pejorative connotations that they now have in popular culture. In 2010, President Barack Obama signed a bill known as Rosa's Law, which required the terms “mental retardation” and “mentally retarded” to be removed from federal use. These terms were replaced with “intellectual disability” and “individual with an intellectual disability,” which is reflected by a change in the DSM-5 as well.Comorbidity
DSM-5 Diagnostic CriteriaIntellectual disability is a disorder with onset during the developmental period that includes both intellectual and adaptive functioning deficits in conceptual, social, and practical domains. The following Criterion ADeficits in intellectual functions, such as reasoning, problem solving, planning, abstract thinking, judgment, academic learning, and learning from experience, confirmed by both clinical assessment and individualized, standardized intelligence testing. Criterion BDeficits in adaptive functioning that result in failure to meet developmental and sociocultural standards for personal independence and social responsibility. Without ongoing support, the adaptive deficits limit functioning in one or more activities of daily life, such as communication, social participation, and independent living, across multiple environments, such as home, school, work, and community. Criterion COnset of intellectual and adaptive deficits during the developmental period. SpecifiersSeverity SpecifierSpecify whether:
Global Developmental DelayGlobal Developmental Delay is a diagnosis for individuals under the age of Unspecified Intellectual DisabilityUnspecified Intellectual Disability is a diagnosis for individuals over the age of MeasurementHow is Intellectual Disability Actually Measured?Intellectual functioning is usually measured with an individually administered and psychometrically valid, comprehensive, and culturally appropriate tests of intelligence. Individuals with intellectual disability have scores that are2 standard deviations (or more) below the population mean. This includes a margin of error (generally ± 5 points).For example, the Intelligence Quotient (IQ) has a mean of 100 and standard deviation of 15. This means a score of 65-75 (70 ± 5) would indicate intellectual disability. However, it is important to note that clinical training and judgment is required to accurately interpret this result, and to rule out other causes of this score. PathophysiologyIntellectual disability can be due to genetic syndromes at birth including: Down syndrome, Rett syndrome, and San Phillippo syndrome (among many others). Other times, it can be acquired due to an illness such as meningitis, encephalitis, or a traumatic brain injury during the developmental period. Prenatal causes include: inborn errors of metabolism, brain malformations, maternal disease or placental disease. Postnatal causes include hypoxic ischemic injury, infections, demyelinating disorders, seizure disorders (e.g. - infantile spasms), severe and chronic social deprivation, toxic metabolic syndromes, and heavy metal intoxications (e.g. - lead, mercury). Differential DiagnosisA diagnosis of intellectual disability should not be presumed simply because of a pre-existing genetic or medical condition. A differential diagnosis includes:
InvestigationsSee main article: Psychoeducational and Intelligence Assessments A comprehensive work up for intellectual disability includes assessing intellectual capacity and adaptive functioning, identifying genetic, non-genetic, and associated medical conditions (such as cerebral palsy and seizure disorders). A prenatal/perinatal history, family pedigree, physical examination, genetic evaluation (karyotype, chromosomal microarray, and/or genetic syndrome tests), metabolic screening, and neuroimaging assessment can also be important investigations. TreatmentBehavioural ManagementMedications, particularly antipsychotics, may be used to manage challenging behaviour such as aggression in individuals with intellectual disability. When the behaviour does not arise from an underlying mental illness, this is off-label use and evidence of efficacy is very poor. Furthermore, these patients face higher risks of drug-related side effects. ResourcesFor Patients
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ArticlesResearchReferencesAmerican Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Arlington, VA. Rosa's Law 82 FR 31910 Glover, G., Bernard, S., Branford, D., Holland, A., & Strydom, A. (2014). Use of medication for challenging behaviour in people with intellectual disability. What IQ score is considered intellectually disabled?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).
What are the 4 levels of an intellectual disability?The terms mild, moderate, severe and profound may be used to describe the severity of a person's intellectual disability.
How does the DSMIn DSM-5, intellectual disability is seen as being at least about two standard deviations or greater below the population, which is approximately an IQ score of 70 or less. Again the emphasis is not specifically on meeting any cutoff score, but rather on how the particular individual presents.
What is the IQ range for mild intellectual disability?Mild intellectual disability
The measured IQ for persons with mild ID is between 50–55 and 70 (based on population mean of 100; 1 standard deviation of 15, and margin of measurement error of ±5) (8,10,13-16).
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