Intellectual Disability (ID)

Definition

• Significantly reduced intellectual functioning with an IQ below 70

• Deficits in adaptive behaviour across areas such as communication, social participation, and self-care

• Onset usually during the developmental period and often accompanied by global developmental delay in two or more domains (motor, cognitive, social, language)

Causes

• Prenatal

  • Prematurity, maternal infections, fetal alcohol spectrum disorders

  • Exposure to teratogens affecting brain development

• Perinatal

  • Hypoxic-ischaemic injury, intracranial haemorrhage

  • Complications during delivery

• Postnatal

  • Lead toxicity, traumatic head injury, severe malnutrition

  • Central nervous system infections (e.g. meningitis, encephalitis)

• Genetic

  • Down syndrome, Fragile X syndrome, other chromosomal abnormalities

  • Inherited metabolic disorders (e.g. phenylketonuria)

• Psychosocial

  • Extreme neglect or prolonged institutional care in early childhood

Investigations

• Chromosomal Microarray

  • First-line genetic test to identify microdeletions or duplications

• Additional Testing (as indicated)

  • Metabolic screening if an inborn error of metabolism is suspected

  • Thyroid function to exclude hypothyroidism

  • Serum lead levels if environmental exposure is possible

  • MRI brain for structural anomalies if clinically relevant

Management

• Referral

  • Involve a paediatrician or developmental specialist for comprehensive assessment

  • Multidisciplinary input from geneticists, allied health, and educational services

• GP Role

  • Early recognition of developmental delays and initiation of investigations (including chromosomal microarray)

  • Coordinate ongoing care and support for families

• Early Intervention

  • Access to speech therapy, occupational therapy, and physiotherapy for skill development

  • Special education programmes tailored to cognitive level

• Support and Planning

  • Guidance on behaviour management and social skills training

  • Assistance with community resources, respite care, and educational entitlements

• Monitoring

  • Regular follow-up to reassess developmental progress, comorbidities (e.g. epilepsy, visual/hearing impairment)

  • Transition planning into adolescence and adulthood, ensuring appropriate vocational and social support