Mental Retardation

Encyclopedia of Childhood and Adolescence, Apr 06, 2001

Besides Down syndrome, the chromosomal condition that most commonly causes mental retardation is fragile X syndrome, in which a segment of the chromosome that determines gender is abnormal. Fragile X syndrome primarily affects males, in whom the incidence of the condition is 1 in 1,000, as opposed to 1 in 2,500 for females. Males with fragile X syndrome tend to have long, thin faces with prominent ears and jaws, and they often have characteristics of autism. Some researchers suspect that as many as 15% of people diagnosed with autism actually have fragile X syndrome. About 20% of genetically caused mental retardation results from single gene mutations, including Tay Sachs disease , phenylketonuria (PKU), and metachromatic leukodystrophy.

Mental retardation may be caused by problems that occur during pregnancy and birth, including maternal nutritional deficiencies, toxemia, infections such as rubella , maternal phenylketonuria (even if the fetus doesn't have the condition), use of drugs or alcohol, maternal injury during pregnancy , extreme prematurity, low birth weight, perinatal injury, or lack of oxygen at birth. Retardation can also be the result of medical conditions and injuries that occur after birth, including metabolic disorders, severe childhood malnutrition, prolonged high fever, near drowning, lead poisoning, severe mental disorders such as autism, and infections such as meningitis that affect the brain. Environmental factors influencing mental retardation include deprivation of physical or emotional nurturance and stimulation. Altogether, there are hundreds of possible causes of, or factors contributing to, mental retardation.

Mentally retarded people are more prone to both physical and mental disorders than the general population. Some of the conditions that cause mental retardation may also be characterized by seizures , hearing problems, congenital heart defects, and other symptoms. Mental disorders are much more common among the mentally retarded than among the general population: an estimated one million Americans have some degree of mental retardation as well as a mental disorder of some kind. The most severely retarded appear to be most at risk for mental disorders, and the more severe the retardation the more serious the disorder. Diagnosis and treatment of these disorders can be especially difficult due to communication problems. In addition, mental illness in the retarded may also be caused by the stresses, frustrations, and loneliness they encounter in daily life. Depression for example, is a common disorder of the mentally retarded, and one that often goes undiagnosed. In spite of their limited intellectual capabilities, retarded children realize that they are different and that other people are often uncomfortable around them. Professional counseling, along with parental love and attention, can help a retarded child maintain a positive self-image, which is crucial to the ability to function effectively with family, peers, and in the larger community.