Mental retardation affects about 1 - 3% of the population. There are many causes omentalretardation, butdoctors find a specific reason in only 25% of cases.

A family may suspect mental retardation if the child's motor skills, language skills, and self-help kills do not seem to be developing, or are developing at a far slower rate than the child's peers. Failure to adapt (adjust to new situations) normally and grow intellectually may become apparent early in a hild's life. In the case of mild retardation, these failures may not become recognizable until school age or later.

An assessment of age-appropriate adaptive behaviors can be made using developmental screening tests.The failure to achieve developmental milestones suggests mental retardation.

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

Risk factors are related to the causes. Causes of mental retardation can be roughly broken down into several categories:

Infections (present at birth or occurring after birth)
Congenital CMV
Congenital rubella
Congenital toxoplasmosis
Encephalitis
HIV infection
Listeriosis
Meningitis