Causes of Mental Retardation

In the United States the prevalence of this disorder is 3:100 people (The Arc, 2001). American Psychiatric Association year 2000 (in Rathus, 2005, h.149-153) states the cause of mental retardation can be caused by:

Down syndrome and other chromosomal abnormalities 
Wade in 2000 declared the most common chromosomal abnormality that causes mental retardation is Down syndrome which is characterized by the presence of excess chromosome or a third chromosome on the 21st chromosome pair, resulting in chromosome number to 47.

Children with Down syndrome can be identified based on certain physical characteristics, such as a round face, wide, flat nose, and a small fold of skin that lead down to the tip section that gives the impression slanted eyes. Protruding tongue, small arms, and a rectangular with short fingers, a curved fifth finger, and the size of the hands and feet are small and disproportionate compared to also be an overall body characteristics of children with Down syndrome. Almost all these children are mentally retarded and many of them have physical problems such as interference with the formation of heart and respiratory difficulties.

Fragile X syndrome and other genetic abnormalitiesFragile 
X syndrome is a common type of inherited mental retardation. This disorder is caused by mutations of genes on chromosome X. a defective gene located on chromosome areas that seem fragile, so-called fragile X syndrome This syndrome causes mental retardation in the 1000-1500 men's and mental barriers in each of 2000-2500 women. Effect of fragile X syndrome ranges from mild learning disorders to severe retardation that can cause a severe speech and function.

Phenylketonuria (PKU) is a genetic disorder that occurs in one in 10,000 births. This disorder is caused by a recessive gene that inhibits a child to engage metabolism. Consequently, phenilalanin phenilpyruvic acid and its derivatives, accumulate in the body, causing damage to the central nervous system resulting in mental retardation and emotional disturbance.

Prenatal factors 
The cause of mental retardation is an infection and maternal drug abuse during pregnancy. Infection usually happens is Rubella, which can cause brain damage. Maternal disease can also cause mental retardation, such as syphilis, cytomegalo virus, and genital herpes. The drugs used during pregnancy the mother can affect the baby through the placenta. Some can cause physical disability and severe mental retardation.

Children whose mothers drank alcohol during pregnancy are often born with fetal syndrome, and is the most obvious case as a cause of mental retardation. Birth complications, such as lack of oxygen or head injury, brain infection, such as encephalitis and meningitis, exposure to toxins, such as paint containing lead is a potential cause of mental retardation.

Psychosocial Factors 
Causes of mental retardation in some cases due to psychosocial factors, such as home environment, or poor social, which do not provide intellectual stimulation, neglect, or violence from parents may be causing or contributing to the development of mental retardation.

Cases related to psychosocial aspects referred to as a retardation-family culture (cultural-familial Retardation). Individuals in poor families lack the need to receive education and skills development. As a result, individuals become mentally retarded because of poverty, did not receive education and prohibitions on certain cultures to develop individual skills.