mental retardation

the state of those whose intellectual powers have failed to develop to such an extent that they are in need of care and protection and require special education. It is also known as mental deficiency and MENTAL HANDICAP . The handicap may be classified according to the intelligence quotient (IQ) as mild (IQ 50-70), moderate to severe (IQ 20-50), and profound (IQ less than 20). Mildly handicapped people often make a good adjustment to life after special help with education. The moderately and severely handicapped usually need much more help and most are permanently dependent on other people, while the profoundly handicapped usually need constant attention. There are very many causes of mental retardation, including DOWN'S SYNDROME , inherited metabolic disorders, brain injury, and gross psychological deprivation; some are preventable or treatable.