Intellectual developmental disorder

Overview & Definition

A seven-year-old is referred because school says he is “behind.” He cannot manage classroom routines. He needs help with toileting and dressing. He struggles to learn letter sounds. His parents ask whether he is “just lazy.” Your job is to decide whether this is intellectual developmental disorder, a specific learning disorder, a sensory problem, autism, deprivation, or more than one of these — and then to open help without waiting for every test result. ^{[6] [7]}

Intellectual developmental disorder (also called intellectual disability) requires three things together: deficits in intellectual functioning, deficits in adaptive functioning, and onset during the developmental period. Adaptive function is not optional decoration. Tassé’s work underlines that intellectual scores and adaptive behaviour are related but not interchangeable; diagnosis needs both. ^{[5] [6]}

Adaptive functioning is what the child can do in daily life across three domains. ^{[5] [6]}

• Conceptual — language, reading, writing, maths, memory, problem-solving, knowledge. ^[5]
• Social — communication, friendship, social judgement, gullibility, following social rules. ^[5]
• Practical — self-care, money and time concepts, transport, safety, school and work routines. ^{[5] [6]}

The historical term “mental retardation” is obsolete in clinical communication. Use person-first or identity-respecting language agreed with the family, and keep the diagnostic criteria precise. ^{[6] [7]}

This page owns the IDD diagnosis, aetiological evaluation and longitudinal medical-home plan. The broad GDD work-up spine is also covered on the linked global developmental delay page — cross-link it rather than cloning every differential table. Screening systems live on the preventive screening leaf; milestone observation craft lives on surveillance pages. ^{[1] [15] [20]}

^{[1] [2] [16]}

References20ShowHide

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3. [3]Manickam K Exome and genome sequencing for pediatric patients with congenital anomalies or intellectual disability: an evidence-based clinical guideline of the American College of Medical Genetics and Genomics (ACMG). Genetics in medicine, 2021.PMID 34211152
4. [4]Maulik PK Prevalence of intellectual disability: a meta-analysis of population-based studies. Research in developmental disabilities, 2011.PMID 21236634
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