ICD-11 Classification for Intellectual Disability (6A00)

Every clinician needs the same anchor point: where does this child's developmental profile sit in the international classification? ICD-11 gives it a precise home.

In short

In ICD-11-MMS, Intellectual Disability is classified under 6A00 — Disorders of Intellectual Development, within the grouping of Neurodevelopmental Disorders. ICD-11 defines it as a group of aetiologically diverse conditions originating during the developmental period, characterised by significantly below-average intellectual functioning and adaptive behaviour that are approximately two or more standard deviations below the mean. Severity is specified — mild (6A00.0), moderate (6A00.1), severe (6A00.2), profound (6A00.3), with provisional and unspecified categories where standardised testing is not feasible.

How ICD-11 frames the diagnosis

A key shift in ICD-11 is the term Disorders of Intellectual Development, replacing the older mental retardation nomenclature, and aligning the diagnostic logic with both intellectual and adaptive functioning rather than IQ alone. Severity is determined by assessing conceptual, social and practical adaptive domains, using appropriately normed and culturally valid instruments wherever available. Where age (early childhood) or co-occurring sensory, motor or communication impairment prevents valid standardised assessment, ICD-11 provides provisional categories — for example 6A00.4, Disorder of intellectual development, provisional — so that support is not delayed pending formal testing. This functional, developmental-period framing sits naturally alongside the WHO ICF model of functioning.

When to refer

Refer a child for structured developmental assessment when global delay is evident across multiple domains, when adaptive skills lag persistently behind age expectations, or when parental and educational concern converge — rather than waiting for a single IQ figure. In early childhood, a global developmental delay descriptor is often more appropriate until reliable standardised intellectual assessment becomes feasible, typically beyond the preschool years.

The Pinnacle way

At Pinnacle Blooms Network, Developmental measurement supports care planning; diagnosis requires an appropriately qualified healthcare professional., under qualified clinician care — never from an app, a form, or this page. Our clinician-administered structured assessment translates a child's profile into a clear baseline and a practical support plan, drawing on 2.5 billion+ data points and 25 million+ therapy sessions across 70+ centres. Explore how the AbilityScore is established and cognitive and developmental therapy pathways.

Trusted sources

WHO ICD-11 for Mortality and Morbidity Statistics, category 6A00, Disorders of intellectual development; CDC developmental milestone guidance; Indian Academy of Pediatrics; American Academy of Pediatrics paediatric developmental guidance.

Next step — To establish a child's developmental baseline and severity profile with clinical rigour, partner with a Pinnacle clinician.

This is general information, not a diagnosis — individual assessment and diagnosis require an appropriately qualified healthcare professional.