WHAT CAUSES MENTAL RETARDATION/DEVELOPMENTAL DISABILITIES?
Causes related to mental retardation are categorized as follows (S. Miller, Personal communication, May 2001): • Genetic conditions – abnormality of genes passed on from parents, errors when genes combine, or from other disorders of the genes caused during pregnancy by infections, overexposure to x-rays and other factors cause mental retardation. Over 500 genetic diseases are associated with mental retardation, including: • PKU (phenylketonuria): a single gene disorder also referred to as an inborn error of metabolism due to a defective enzyme. • Down syndrome: a chromosomal disorder caused by too many or too few chromosomes, or by a change in structure of a chromosome. • Fragile X syndrome: a single gene disorder located on the X chromosome that is the leading inherited cause of mental retardation. Other factors that may cause or increase the possibility of mental retardation include: • Substance abuse or usage – use of alcohol, tobacco, or other drugs during pregnancy. • Sexually tra
