Because 3 out of 100 people in US have an intellectual disability and also nearly 614,00 children ages 3- 21 have some level of intellectual disability and need special education in schools (NICHCY, 2009') it is valid appreciable the significances of mental retardation. Indeed 1 out of every 10 children who need special education has some form of intellectual disability.
Indeed as aforesaid it is marked significantly below average score on test of mental ability and limitation in function in area of daily living as making discussions, participate in leisure, social, school and work activities and areas of personal health and safety . People with this disorder have different degree of impairment and recognizing them is more easy thought classifying a person's level of function. So intellectual disability it is rating from mild to profound, also stating the disability thought intelligence (IQ) or thought types and amount of support they need. Support is categorized such as intermittent which means occasional support, limited which means supported such as a day program in a sheltered workshop, extensive which means daily, ongoing support and pervasive which means a high level of supported for all activities if daily, including full time nursing care. Following the international classification classes of IQ mental retardation is profound IQ below 20 ;severe with IQ 20 -34 ; moderate with IQ 35-49; mild with IQ 0-69 and borderline intellectual functioning 70 -70 IQ mental retardation. According to date, adequacy on IQ test scores estimated that 3 % of the total population are considered in this vulnerable group. Otherwise, adequacy is needed for supporting estimated only 1 % of people that are classified as cognitive limitation.
Different issues should be considered in mental retardation, following these health issues, social issues and psychological issues as essential parts or participation could gain appropriate picture for these disorder. Observing health issues following fact are relevant for appropriate approach. Down syndrome, fetal alcohol syndrome and Fragile X syndrome the three most common inborn causes. Others cause could be genetic condition, consequences of abnormal genes inherited from parent or gene combinations errors. Prevalence is presence in genetic conductions such as Down syndrome, Klienfelter's syndrome, Fragile X syndrome, neurofibromatosis, congenital hypothyroidism, Willliams syndrome, Phenyilketonuria, and Prader-Willi syndrome. Also, other genetic condition could be included such as Phelan-McDermid syndrome, Mowat-Wilson syndrome, genetic ciliopathy. Rarely abnormalities in X or Y chromosomes cause disabilities, appropriately 48, XXXX and 49, XXXXX syndrome can affect girls and 47, XYY, 49, XXXXY, or 49, XYYYY can affect boys, worldwide. Also, problems during pregnancy can establish mental retardation such as inappropriate fetus cell dividing during growing or women who consume alcohol or gets infection such as rubella can have baby with these disorder. Problems during labor and birth, such as insufficient oxygen could establish development disability result of brain damage. Exposure to toxins such as lead and mercury can cause mental retardation, or disease such as whooping cough, measles or meningitis can cause mental disability if inappropriate medical care is established. Iodine deficiency, spared in 2 billion people worldwide is leading preventive cause of mental disability, in areas