Mental retardation

A neurodevelopmental disorder characterized by significantly impaired intellectual functioning (IQ <70) and deficits in adaptive behavior affecting conceptual, social, and practical skills, with onset during the developmental period (before 18 years of age).

Causes

• Genetic causes

  • Down syndrome

  • Fragile X syndrome

  • Phenylketonuria (PKU)

  • Other chromosomal abnormalities

  • Inherited metabolic disorders

  • Genetic syndromes affecting brain development

• Prenatal causes

  • Fetal alcohol spectrum disorder

  • Congenital infections: Rubella, CMV, syphilis

  • Maternal malnutrition

  • Maternal use of illicit drugs

  • Environmental toxins: Lead, mercury, heavy metals

  • Maternal endocrine or metabolic disorders affecting fetal development

• Perinatal causes

  • Birth-related hypoxia or oxygen deprivation

  • Extreme prematurity

  • Birth trauma

  • Neonatal complications affecting brain development

• Postnatal causes

  • Meningitis

  • Encephalitis

  • Traumatic brain injury

  • Lead poisoning

  • Mercury poisoning

  • Severe nutritional deficiencies

• Other causes

  • Cerebral malformations

  • Epileptic encephalopathies

  • Metabolic disorders