The reasoning (modern framing)
Disorders of intellectual development = significant limitations in intellectual functioning AND adaptive behaviour (conceptual, social, practical), onset during development. Severity is defined by adaptive functioning, not an IQ cut‑off — abandon the old rigid IQ bands. Two people with similar psychometrics can differ markedly in independence.
Keep three entities distinct
| Entity | Core problem |
|---|---|
| Intellectual developmental disorder | Global intellectual + adaptive limitation |
| Global developmental delay | Young child, delay across multiple domains, definitive assessment premature |
| Specific learning disorder | Isolated academic‑skill deficit (dyslexia/dyscalculia/dysgraphia) with otherwise intact intellect |
The clinically pivotal separation
Assessment
Standardised cognitive and adaptive measures, developmental history, and screening for reversible/contributory factors (hearing/vision, neglect, treatable medical causes) plus comorbid ADHD/ASD/mental illness.
Pitfalls
- Using IQ alone to define severity.
- Labelling a specific learning disorder as intellectual disability.
Pearls
- 🎯 Adaptive functioning, not IQ, sets severity.
- 🩺 Specific learning disorder ≠ low intelligence.
Next → The eating disorders — where psychiatric diagnosis carries acute medical risk (Concept 33).