Mental Retardation (Causes)

Causes of mental retardation are numerous, but a specific reason for mental retardation is determined in only 25 percent of cases.

Failure to adapt normally and grow intellectually may become apparent early in life or, in the case of mild retardation, may not become recognizable until school age or later. An assessment of age-appropriate adaptive behaviors can be made by the use of developmental screening tests. The failure to achieve developmental milestones is suggestive of mental retardation.

A family may suspect mental retardation if motor skills, language skills, and self-help skills do not seem to be developing in a child or are developing far more slowly than among the child's peers.

The degree of impairment from mental retardation ranges widely, from profound impairment to mild or borderline retardation. Less emphasis is now placed on degree of retardation and more on the amount of intervention and care required for daily life.

Causes of mental retardation can be roughly broken down into several categories:

  • unexplained (the largest category)
  • trauma (prenatal and postnatal) such as oxygen deprivation before, during or after birth
  • infection (congenital and postnatal)
  • Chromosomal abnormalities
  • Genetic abnormalities and inherited metabolic disorders
  • metabolic disorders
  • toxins such as lead or mercury poisoning
  • nutritional deficits such as severe malnutrition
  • environment
Mental Retardation. Last reviewed 12/31/1969
  • National Institutes of Health
  • National Library of Medicine