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Mental retardation (MR), also referred to as intellectual disability, is defined as a disorder in which people have limitations in their mental functioning and in their adaptive behaviors. These limitations usually begin during developmental years and are often observed before a person is 18. There are generally four levels of mental retardation: the mild, the moderate, the severe, and the profound forms of mental retardation.
The mental functioning of people with varying levels of mental retardation is usually assessed by their ability to learn, to reason, and to solve problems. This is commonly measured with the use of the intelligence quotient (IQ) test. Adaptive behaviors are the important skills needed by a person to function effectively in his daily life. These include social skills, communications skills, and practical skills, such as self-care and money management.
Individuals diagnosed with mild mental retardation are those with IQ scores of 50 to 70. Most of them have no physical signs of abnormality. They are capable of acquiring many social and practical skills, and they can also learn useful mathematical and reading abilities up to the third- and sixth-grade level. In school, they do not need to be given continuous support. Many can live independently and become self-sufficient with some assistance from the community.
Those with moderate mental retardation have an IQ measurement between 35 to 49. Many of them may show some delays in speech development. They may need a small amount of assistance in school, but they can acquire some communication skills and can join in simple activities. Many can also become self-sufficient, but with constant supervision and support.
The diagnosis of severe mental retardation is commonly given to individuals with an IQ of 20 to 34. They usually have obvious developmental delays, like impaired walking, and may have limited communication skills. Most of them may need assistance and supervision every day, although they can be taught simple self-care routines.
Of the four levels of mental retardation, those with profound mental retardation, are often the ones who need support and assistance 24 hours a day. Their IQ score is less than 20, and most of them may have abnormalities present during birth. They are often incapable of self-care, and are usually provided with a personal attendant to offer close supervision.