Intellectual Developmental Disorder and Global Developmental Delay
Intellectual developmental disorder involves difficulties in intellectual functions and adaptive functioning that begin during development. Global developmental delay is a separate, provisional diagnosis for some children under five.
Function matters more than one score
Assessment considers conceptual skills such as language, learning, time and money; social understanding and relationships; and practical skills such as self-care, organisation and safety. Severity is based on everyday adaptive functioning and the support a person needs—not on IQ alone.
Global developmental delay is used before age five when a child is delayed across several domains but reliable systematic assessment of intellectual functioning is not yet possible. It requires periodic reassessment. Neither term reduces a child to a number; both should clarify strengths, needs and access to support.
Multidisciplinary assessment
- Intellectual developmental disorder requires evidence of difficulties in intellectual functions and adaptive functioning, with onset during the developmental period.
- Information comes from standardised assessment and actual functioning across home, school and community, interpreted in the person’s language and cultural context.
- Hearing, vision, communication, motor and medical needs are assessed, with genetic or neurological investigation when history and findings indicate it.
- Loss of previously acquired skills is not treated as ordinary delay and needs timely medical investigation.
Support across life stages
Early developmental support, special education, speech and language therapy, occupational therapy or physiotherapy are selected according to specific needs and should not wait for a final aetiological diagnosis. Skills are taught in clear steps with repetition, visual support and practice in real settings.
Planning continues through adolescence and adulthood, including education, work, relationships, health, money, decision-making and the appropriate level of supported or independent living. Accessible communication and supported decision-making promote dignity, self-determination and the greatest realistic autonomy.
When to seek help
Speak with a paediatrician when milestones are not being reached, delays affect several domains or family and school have concerns about learning and daily skills. Sudden regression, new weakness, seizures, altered awareness or a rapid change in function requires immediate medical assessment.