An IQ level below 70 signifies a deficiency in adaptive functioning.

The possible causes of mental retardation may be attributed to three genetic disorders - down syndrome, fetal alcohol syndrome and fragile X syndrome. The impaired genetics conditions are believed to be the most common causes of mental retardation. In addition, researchers have identified few other causes that may profoundly heighten the risk for developing mental retardation in a child. Difficulties during or following pregnancy may also result in severe problem in the fetus such as genetic mutation occurring during fetal development or if the mother suffers from rubella during her pregnancy. In addition, if the baby is not exposed to sufficient oxygen during pre and post-birth phases, it may lead to developmental disability following brain damage. Malnutrition or iodine deficiency may contribute to the development of mental retardation. Institutionalization at a very young age as well as sensory deprivation...
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