Mental Retardation

Mental retardation is a permanent condition characterized by subaverage intelligence, which causes limitations in learning and adaptive functioning. Individuals with mental retardation may be able to live independently in the community and obtain various levels of employment, depending on the level of severity; as severity increases, the need for training and support may be required to complete even simple, daily tasks. This section describes the health status of individuals living with mild, moderate, or severe mental retardation.

Mental retardation occurs in all races and cultures, although there is a higher prevalence overall among males than females. Approximately 1-3% of the population are affected;7,121,122 of all cases, the majority (about 85%)7 are classified as having mild severity;122 approximately 10% and 4% of cases have moderate and severe mental retardation, respectively.7 The time of onset typically depends on the cause of the mental retardation. In general, mental retardation is caused by any condition or event that impairs the development of the brain before birth (prenatal), during birth (perinatal), or in childhood (postnatal). Specifically, potential causes include, but are not restricted to, chromosomal deficits (Down syndrome), inherited disorders (Fragile X syndrome, hypothyroidism), errors of metabolism, brain injury or infection (insufficient oxygen during birth, meningitis), prematurity or low birth weight, fetal malnutrition, drug or alcohol misuse during pregnancy (fetal alcohol syndrome), maternal infections (rubella or hypertension), and severe emotional neglect or abuse (including under-stimulation of the infant/child). Unfortunately, in many cases, no specific cause can be identified,7,121 although the likelihood of identifying the particular cause increases with the severity of mental retardation.