Mental Retardation: Causes and Prevention

By — Pearson Allyn Bacon Prentice Hall
Updated on Jul 20, 2010

Mental retardation is caused by many factors; many of these are known, but others remain unidentified (The Arc, 2005). The link between the identification of specific causes of mental retardation and the development and implementation of preventive measures is clear. When a cause is identified, ways to prevent the debilitating effects of cognitive disabilities have often followed soon after. But it takes action for solutions actually to prevent or reduce the impact of the condition.


According to The Arc, a parent organization advocating for individuals with mental retardation, several hundred causes of mental retardation have been discovered, but for about one-third of those affected the cause is unknown (The Arc, 2005). Of those known causes, three conditions—explained later in this section—are the most common reasons for mental retardation:

  1. Down syndrome
  2. Fragile X syndrome
  3. Fetal alcohol syndrome

Many different systems for organizing the causes of mental retardation can be applied. Sometimes they are divided into four groups: socioeconomic and environmental factors, injuries, infections and toxins, and biological causes. AAMR divide them instead into three groups by time of onset—that is, by when the event or cause first occurred (AAMR, 2002):

  1. Prenatal: causes that occur before birth
  2. Perinatal: causes that occur during the birth process
  3. Postnatal: causes that happen after birth or during childhood

Prenatal causes exert their effects before birth. Examples include genetic and heredity, toxins taken by the pregnant mother, disease, and neural tube defects. Genetics and heredity include conditions such as fragile X syndrome and Down syndrome, as well as phenylketonuria (PKU). Prenatal toxins include alcohol, tobacco, and drug exposure resulting from the behavior of the mother during pregnancy. Diseases and infection, such as HIV/AIDS, can devastate an unborn baby. Neural tube disorders, such as anencephaly (where most of the child's brain is missing at birth) and spina bifida (incomplete closure of the spinal column), are also prenatal causes of mental retardation.

Perinatal causes occur during the birthing process. They include birth injuries due to oxygen deprivation (anoxia or asphyxia), umbilical cord accidents, obstetrical trauma, and head trauma. They also include low birth weight.

Postnatal causes occur after birth. The environment is a major factor in many of these situations. Child abuse and neglect, environmental toxins, and accidents are examples of postnatal causes. An additional reason for being identified as having mental retardation is societal biases, particularly toward diverse students.

Now let's turn our attention to some major causes of mental retardation across the three periods of onset. In particular, let's think about some genetic causes, both prenatal and postnatal toxins, low birth weight, and child abuse. Finally, we will briefly return to the situation of Black youngsters and their risk for being identified as having mental retardation.

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