Variations and Characteristics of Mental Retardation

21 Trisomy means that each cell in the body has three copies of chromosome 21, not two normal copies (NLM, 2012). Although most cases of Down's syndrome are not hereditary, random events occur when ova and sperm connect (Sue, Sue, & Stanley, 2010). Of the approximately 800 children born, the prevalence is 1, and for women with children over 39 years old, the prevalence is usually increasing. Women can receive screening tests during pregnancy, but this process is considered highly dangerous for both mothers and children and does not always detect the presence of Down's syndrome (Sue, Sue, & Stanley , 2010).

Approximately 30% of cases of mental retardation are caused by genetic factors. Mental retardation may be caused by hereditary genetic abnormalities such as fragile X syndrome. Vulnerable X is a chromosomal abnormality that determines gender and is the most common genetic cause of mental retardation. Single genetic abnormalities, such as phenylketonuria (PKU) and other congenital metabolic abnormalities, may also cause mental retardation if not detected and treated early. It is possible that accidental or mutation in gene development may also cause growth inhibition. An example of such an accident is additional development

Mental retardation may be caused by various factors, but there are more general factors than other factors. Mental retardation may be caused by abnormal genes inherited from parents, errors in gene binding, or other causes. It may also cause mental retardation when the baby does not properly develop in the womb. There may be problems with the way the baby's cells divide during growth and women who drink alcohol or rubella during pregnancy may have infant with mental retardation. If there is a problem with the baby at birth or childbirth, such as lack of sufficient oxygen, the child may have caused mental retardation. Mental retardation can also be caused by extreme malnutrition, lack of adequate medical care, or exposure to toxic substances such as lead and mercury. (NICHCY 2)

The American Mental Retardation Association (AAMR) has developed another widely accepted diagnostic classification system for mental retardation. The AAMR classification system focuses on the abilities of people with mental disorders. It is not his or her limit. These categories represent the level of support required. They are as follows. Intermittent support, limited support, extensive support and universal support. To some extent, the AAMR classification reflects DSM-IV-TR classification. For example, intermittent support is sometimes necessary to support during stress and crisis, perhaps for people with intellectual disabilities. This is the type of support that most moderate mentally disabled people usually require. On the other hand, for people with mental retardation, universal support or lifelong support for most areas of adaptation is necessary. The AAMR classification system refers to "intelligent function less than or equal to average" as an IQ of 70 to 75 or less.