There are four levels of mental retardation - mild, moderate, severe, and profound. Based on the 1990 U. S. Census, an estimated 6. 2 to 7. 5 million people have mental retardation.
Causes of mental retardation range from genetic disorders to lead poisoning, but The Arc states that the three major causes are Down Syndrome, Fetal Alcohol Syndrome, and Fragile-X. Down Syndrome - Down Syndrome, the most common cause of mental retardation, is a condition caused by a chromosomal abnormality in which, for some unexplained reason, cell development results in 47 instead of 46 chromosomes. This extra chromosome affects the orderly development of the brain and body. Fetal Alcohol Syndrome - Fetal Alcohol Syndrome (FAS) is the name given to a group of physical and mental birth defects that are the direct result of a woman's drinking alcohol during pregnancy. These mental and physical birth defects can include mental retardation, growth deficiencies, central nervous system dysfunction, craniofacial abnormalities and behavioral maladjustments. Fragile-X - In 1991, scientists discovered the gene (called FMR 1) that causes Fragile-X.
In individuals who have Fragile-X syndrome, a defect in FMR 1 shuts the gene down, preventing it from manufacturing the protein that it normally makes. Some genetic disorders are associated with mental retardation, chronic health problems and developmental delay. Because of the complexity of the human body, there are no easy answers to the question of what causes mental retardation. Mental retardation is attributable to any condition that impairs development of the brain before birth, during birth or in the childhood years (The Arc, 1993). As many as 50 percent of people with mental retardation have been found to possess more than one causal factor (A AMR, 1992). Some research has determined that in 75 percent of children with mild mental retardation the cause is unknown (K ozma & Stock, 1993).
Since the brain is such a complex organ, there are a number of genes involved in its development. Consequently, there are a number of genetic causes of mental retardation. Most identifiable causes of severe mental retardation (defined as an IQ of 50 or less) originate from genetic disorders. Up to 60 percent of severe mental retardation can be attributed to genetic causes making it the most common cause in cases of severe mental retardation (Moser, 1995).
People with mild mental retardation (defined as an IQ between 50 and 70-75) are not as likely to inherit mental retardation due to their genetic make-up as are people with severe mental retardation. People with mild mental retardation are more likely to have the condition due to environmental factors, such as nutritional state, personal health habits, socioeconomic level, access to health care and exposure to pollutants and chemicals, rather than acquiring the condition genetically (Nelson-Anderson & Waters, 1995). Two of the most common genetically transmitted forms of mental retardation include Down syndrome (a chromosomal disorder) and fragile X syndrome (a single-gene disorder). Over 7, 000 genetic disorders have been identified and catalogued, with up to five new disorders being discovered every year (McKusick, 1994). Genetic disorders are typically broken down into three types: Chromosomal, single-gene and multi factorial. Chromosomal disorders affect approximately 7 out of every 1, 000 infants.
The disorder results when a person has too many or too few chromosomes, or when there is a change in the structure of a chromosome. Half of all first-trimester miscarriages or spontaneous abortions occur as a result of a chromosome abnormality. If the child is born, he or she usually has multiple birth defects and mental retardation. During the Middle ages (476 - 1799 A. D. ) the status and care of individuals with mental retardation varied greatly.
Although more human practices evolved (i. e. , decreases in infanticide and the establishment of foundling homes), many children were sold into slavery, abandoned, or left out in the cold. Toward the end of this era, in 1690, John Locke published his famous work entitled An Essay Concerning Human Understanding. Locke believed that an individual was born without innate ideas. The mind is a tabula rasa, a blank slate.
This would profoundly influence the care and training provided to individuals with mental retardation. He also was the first to distinguish between mental retardation and mental illness; "Herein seems to lie the difference between idiots and madmen, that madmen put wrong ideas together and reason from them, but idiots make very few or no propositions and reason scarce at allA cornerstone event in the evolution of the care and treatment of the mentally retarded was the work of physician Jean-Marc-Gaspar d Itard (Sheerenberger, 1983) who was hired in 1800 by the Director of the National Institutes for Deaf-Mutes in France to work with a boy named Victor. Victor, a young boy, had apparently lived his whole life in the woods of south central France and, after being captured and escaping several times, fled to the mountains of Aveyron. At about age 12, he was captured once again and sent to an orphanage, found to be deaf and mute, and moved to the Institute for Deaf-Mutes. Some types of mental retardation can be prevented but there are no real cures yet-although researchers continue to search for one..