Children at Risk
Mental retardation occurs in upper and lower socioeconomic classes, except that certain etiological factors (e.g., lead poisoning and premature births) are linked to lower socioeconomic class. Individuals with mental retardation exist in all cultures, educational, racial and ethnic groups.
The prevalence of mental retardation in adults has been estimated at approximately 1%, or roughly 1 in 100. However, as many as 3% of school-age children are diagnosed as mentally retarded. The difference between child and adult rates may be due to the fact that some children may improve their adaptive abilities so that the diagnosis no longer applies.
Mental retardation is more common in males, with a male-to-female ratio of 1.5:1.