Postnatal Causes of Learning Disability (Intellectual Disability)

Postnatal causes of learning or intellectual disability include head injury, infections, neurodegeneration, and toxicities. A study on the causes of developmental disability found bacterial meningitis, child battering, vehicle-related injuries, and otitis media as the most common causes. However, a developmental disability is a broader term that can include motor developmental disabilities too. The results still give us an idea as this overlap heavily with causes of pure intellectual disability. See Table 1.

Table 1: Most Common Causes of Developmental Disability
Bacterial meningitis	31%
Child battering	15%
Motor-vehicle- related injuries	11%
Otitis media	11%
Postnatal causes of developmental disabilities in children aged 3-10 years -- Atlanta, Georgia, 1991. MMWR Morb Mortal Wkly Rep 1996 Feb 16 45 130134

Head injury

1. Traumatic (accidental) brain injury; one of the most preventable causes of intellectual disabilities.
2. The shaken baby syndrome is the most common cause of non-accidental head injury that affects developing brains. 
3. They classify postnatal hypoxia as a perinatal cause if this occurs immediately following birth. However, if it occurs later, we may classify it as another postnatal cause of intellectual disability. 

Infections

1. Meningitis, especially bacterial meningitis, is one of the most common causes of intellectual disability. 
2. Encephalitis, that might be viral can also cause intellectual disability. At a later age, the international classification of disease categories the sequelae of encephalitis under organic mental conditions as a postencephalitic syndrome. 

Degenerative or demyelinating disorders 

Rett syndrome 

Signs of intellectual (learning) disability appear in girls with Rett syndrome at around 18 months to four years of age. Rett syndrome is a genetic disorder that occurs to due MeCP2 gene mutation; it is prenatal, but the appearance of intellectual disability is postnatal. 

Epilepsy

Children with frequent recurrent epileptic fits, for example, those with infantile spasms may develop intellectual disability because of brain injury. Children who experience more frequent fits and those who have more severe seizures are more likely to develop seizures than others. 

Toxic-Metabolic Disorders

Lead poisoning 

Lead poising could occur in areas where they still use lead in gas and other chemicals. Lead poising is a highly preventable cause of intellectual disabilities. 

Malnutrition

Malnutrition is a relevant cause of intellectual disability in countries with chronic malnutrition, it is a rare cause of intellectual disabilities overall, especially in developed countries. 

Environmental Deprivation

Non-stimulating environments impact intellectual development, for example, long-term institutional care. Severe long-term institutional deprivation could more likely cause intellectual disability than less severe brief institutionalisation. 

References

Postnatal Causes of Developmental Disabilities in Children (CDC)

Intellectual Disability: Causes (asha.org)

POSTNATAL CAUSES OF DEVELOPMENTAL DISABILITY. (jwatch.org)