6A00.2

ICD-11 MMS 2026-01

Disorder of intellectual development, severe

Description

A severe disorder of intellectual development is a condition originating during the developmental period characterised by significantly below average intellectual functioning and adaptive behaviour that are approximately four or more standard deviations below the mean (less than approximately the 0.003rd percentile), based on appropriately normed, individually administered standardized tests or by comparable behavioural indicators when standardized testing is unavailable. Affected persons exhibit very limited language and capacity for acquisition of academic skills. They may also have motor impairments and typically require daily support in a supervised environment for adequate care, but may acquire basic self-care skills with intensive training. Severe and profound disorders of intellectual development are differentiated exclusively on the basis of adaptive behaviour differences because existing standardized tests of intelligence cannot reliably or validly distinguish among individuals with intellectual functioning below the 0.003rd percentile.

Coding note from above levels

Use additional code, if desired, to identify any known aetiology.

Index terms

  • Disorder of intellectual development, severe
  • Severe mental retardation
  • behavioural disorder in severe mental retardation
Show allHide
  • severe mental handicap

Exclusions from above levels

  • http://id.who.int/icd/entity/546689346 – Dementia
  • QE62 – Uncomplicated bereavement
  • QE84 – Acute stress reaction

Sibling codes

  • 6A00.0 – Disorder of intellectual development, mild
  • 6A00.1 – Disorder of intellectual development, moderate
  • 6A00.3 – Disorder of intellectual development, profound
  • 6A00.4 – Disorder of intellectual development, provisional
  • 6A00.Z – Disorders of intellectual development, unspecified

Foundation entity

Disorder of intellectual development, severe – http://id.who.int/icd/entity/1508286189

Part of: 6A00: Disorders of intellectual development › 06: Mental, behavioural or neurodevelopmental disorders