Intellectual disability
Significant limitations in intellectual functioning and adaptive behaviour, with severity based on adaptive functioning across daily domains, not IQ score alone.
What it is
Intellectual disability involves significant limitations both in intellectual functioning (reasoning, learning, problem-solving) and in adaptive behaviour, with onset during the developmental period. Severity is determined primarily by adaptive functioning across conceptual, social, and practical domains — not by IQ score alone.
Common symptoms & concerns
- Conceptual, social, and practical skills lagging same-age peers, with most individuals achieving functional academic skills with support
- Conceptual skills markedly behind peers, with noticeably limited social and communication skills
- Limited conceptual, language, and pre-academic skills, requiring substantial daily-living support
- Significant deficits across all domains with round-the-clock support needed at the most involved level
Assessment & care
Assessment approach
Assessment combines standardized testing of intellectual functioning with an evaluation of adaptive behaviour across conceptual, social, and practical domains, since severity is based on adaptive functioning, not IQ score alone.
In-scope care
In-scope care includes behaviour therapy, social skills training, and parent-training programs, with family-centred psychoeducation available as an adjunct. Behaviour therapy and social skills training build functional and adaptive skills directly while parent-training keeps strategies consistent at home, where most adaptive-behaviour gains are actually used.
Treatments used
Related questions
Diagnosis requires both standardized testing of intellectual functioning and an assessment of adaptive behaviour across conceptual, social, and practical domains, with onset during the developmental period.
No, though the two can co-occur. Intellectual disability centres on limitations in reasoning, learning, and adaptive skills, while autism centres on differences in communication, social interaction, and behaviour.
No, the severity level describes support needs at the time of assessment, not a fixed long-term outcome; it is reassessed as the child develops.