Mental retardation (MR) is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviours. It has historically been defined as an Intelligent quotient score under 70.Once focused almost entirely on cognition the definition now includes both a component relating to mental functioning and one relating to individuals' functional skills in their environment. As a result, a person with a below-average intelligence quotient may not be considered mentally retarded.
Mental Retardation is defined as,"significantly sub average general intellectual functioning existing concurrently with deficits in adaptive behaviour and manifested during the developmetal period."-AAMD
"Mental retardation is a state of arrested or incomplete development of the mind/intellect."
For the diagnosis to apply ,these problems must have begun before the age of 18 years.Mental Retardation is thus defined in terms of level of performance as well intelligence.The definition says nothing about causal factors ,which may be primarily biological,psychosocial,sociocultural,or a combination of these.By Definition ,any functional equivalent of mental retardation that has its onset after age 17 must be considered a dementia rather then Mental retardation.The distinction is an important one,because the psychological situation of a person who acquires a pronounced impairment of intellectual functioning after attaining maturity is vastly different from that of a person whose intellectual resources were subnormal throughout all or most of his or her development.
THE VARIOUS LEVELS OF MENTAL RETARDATION ,AS DEFINED IN DSM-4 TR ARE AS FOLLOWS;
DIAGNOSED LEVEL OF MENTAL RETARDATION| CORRESPONDING IQ RANGE| Mild retardation | 50-55 to approximately 70|
Moderate retardation | 30-40 to 50-55|
Severe retardation | 20-25 to 35-40|
Profound retardation| 20-25 to 35-40 below 20-25|
Mild Mental Retardation –Mildly retarted individuals constitute by far the largest number number of those diagnosed as mentally retarted.Within the educational context,people in this group are considered "educable",and their intellectual levels as adults are comparable to those of average 8 to 11 year old children.Statements such as the latter,however,should not be takrn too literally.A mildly retarted adult with a mental age of,say,10 (that is,intelligence test performance is at the level of the average )may not infact be comparable to the normal 10-year-old in information –processing ability or speed(Weiss,Weisz,and Bromfield,1986).On the other hand,he or she will normally have had far more experience in living ,which would tend to raise the IQ score. The social adjustment of mildly retarted people often approximates that of adolescents,although they tend to lack normal adolescents imagination ,invetiveness and judgement.Ordinarily,they do not show signs of brain pathalogy or other physical anomalities,but often they require some measure of supervision because of their limited mabilities to foresee the consequences of their actions. Moderate Mental Retardation-Moderately retarded indiduals are likely to fall in the educational catergory of "trainable",which means that they are presumed able to master certain routine skills such as cooking or minor janitorial work if provided specialised instruction in these activities .In adult life ,individuals classified as moderately retarded attain intellectual levels similar to those of average 4 – 7 year old children.Although some can be taught to read and write a little and may manage to achieve a fair command of spoken language ,their rate of learning is slow and their level level of conceptualising is extremely limited.They usually appear clumsy and ungainly,and they suffer from deformities and poor motor coordination.Some of these moderately retarded...