What Causes Mental Retardation?

Doctors have found many causes of mental retardation. The most common are:

• Genetic conditions. Sometimes mental retardation is caused by abnormal genes. These abnormal genes may be inherited or due to errors when genes combine, or other reasons. Examples of genetic conditions are Down syndrome, fragile X syndrome, and phenylketonuria (PKU).
• Problems during pregnancy. Some babies do not develop inside the mother properly. For example, there may be a problem with the way the baby's cells divide as it grows. Or the pregnant mother may have drank alcohol. Or she may have had a serious infection, like rubella, while pregnant.
• Problems at birth. If a baby has problems during labor and birth he or she may have mental retardation. For example, a baby may not get enough oxygen during birth.
• Health problems. Childhood diseases, like meningitis or the measles, can be a cause. Other causes are extreme malnutrition (not eating right) or lack of medical care. Also exposure to poisons like lead or mercury are causes.

Adapted from the National Dissemination Center for Children with Disabilities, Mental Retardation Fact Sheet (FS8). Accessed on 11/12/04, http://www.nichcy.org/pubs/factshe/fs8txt.htm#parents.