intellectual developmental disorders

Last edited 01/2021 and last reviewed 08/2023

Mental retardation is an emotive term defined as intellectual impairment starting in early childhood.

• it is proposed that this term will be eliminated in international classifications of diseases and disorders (1)

This condition was classified in the ICD 10 coding system as follows:

317 Mild Mental Retardation IQ 50 - 70 (synonyms include feeble-minded, moron, high grade defect, and mild mental subnormality)

318 Other Specified Mental Retardation

• 318.0 Moderate mental retardation IQ 35-49 (synonyms: imbecile; moderate mental subnormality)
• 318.1 Severe mental retardation IQ 20-34 (synonym: severe mental subnormality)
• 318.2 Profound mental retardation IQ under 20 (synonyms: idiocy; profound mental subnormality)

Note though that the diagnostic term 'mental retardation' is finally being eliminated in the upcoming international classifications of diseases and disorders.

• the term 'mental retardation' was introduced by the American Association on Mental Retardation in 1961 and soon afterwards was adopted by the American Psychiatric Association (APA) in its Diagnostic and Statistical Manual for Mental Disorders (DSM-5)
  • mental retardation replaced older terms such as feeblemindedness, idiocy, and mental subnormality that had become pejorative
• the ICD-11 working group proposes replacing mental retardation with intellectual developmental disorders (IDDs), a term it defines as 'a group of developmental conditions characterized by significant impairment of cognitive functions, which are associated with limitations of learning, adaptive behavior and skills'
• the new term proposed for DSM-5 is intellectual disability (ID)/IDD. The new DSM-5 category is synonymous with the proposed ICD-11 diagnosis of IDDs, in that it refers to a health condition or disorder
  
  
• 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:

• 1) Deficits in intellectual functioning—“reasoning, problem solving, planning, abstract thinking, judgment, academic learning, and learning from experience”—confirmed by clinical evaluation and individualized standard IQ testing;

• 2) Deficits in adaptive functioning that significantly hamper conforming to developmental and sociocultural standards for the individual's independence and ability to meet their social responsibility; and

• 3) The onset of these deficits during childhood
  
  

• 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)

Reference:

• Salvador-Carulla L, Reed GM, Vaez-Azizi LM, et al. Intellectual developmental disorders: towards a new name, definition and framework for 'mental retardation/intellectual disability' in ICD-11. World Psychiatry 2011; 10:175-180.
• AAIDD (American Association on Intellectual Developmental Disabilities). Intellectual disability: Definition, classification, and systems of supports. Washington, DC: AAIDD; 2010.
• APA (American Psychiatric Association). Diagnostic and statistical manual of mental disorders. fifth ed. Washington, DC: APA; 2013.