Mental Retardation: Causes and Prevention (page 3)

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

Low Birth Weight

Low birth weight is a major risk factor for disabilities and is definitely associated, with poverty and with little or no access to prenatal care (Children's Defense Fun. [CDF], 2004). Medical advances of the 1980s have greatly increased the likelihoood that infants born weighing less than 2 pounds will survive. These premature, very small infants make up less than 1.4 percent of all newborns and are at great risk for disabilities, including mental retardation (Allen, 2002). However, babies born between 3 and 5 pounds also are at greater risk for disabilities than many doctors and parents believe. Babies with moderately low birth weight represent 5 to 7 percent of all births, but they represent 18 to 37 percent of children with cerebral palsy and 7 to 12 percent of children with cerebral palsy who also have mental retardation. Whereas about 5 percent of White babies have moderately low birth weight, between 10 and 12 percent of African American babies are born early and have low birth weight.

Child Abuse and Neglect

Abused children have lower IQs and reduced response rates to cognitive stimuli (CDF, 2001, 2004). In one of the few studies of its kind, Canadian researchers compared abused children with those not abused, and the results of abuse became clear (Youth Record, 1995). The verbal IQ scores were very different between the two groups of otherwise matched peers: The abused children had an average total IQ score of 88, whereas the average overall IQ of their nonabused peers was 101; and the more abuse, the lower the IQ score. The link between child abuse and impaired intellectual functioning is now definite, but the reasons for the damage are not known. Rather than resulting from brain damage, the disruption in language development caused by the abusive situation may be the source of permanent and profound effects on language ability and cognition. Or the abuse may itself be a result of the frustration often associated with raising children with disabilities. Remember, the connection between neglect and mental retardation has long been recognized and is part of the early history and documentation of this field.

Discrimination and Bias

It is important to remember that many subjective reasons account for students' placement in special education. There is little doubt that poverty and its risk factors are clearly linked to disabilities (CDF, 2004; National Research Council, 2002). It is also true that culturally and linguistically diverse children are overrepresented in some categories of special education (Hosp & Reschly, 2002, 2003; U.S. Department of Education, 2005a). This situation is particularly true for Black students, who are almost three times more likely to be identified as having mental retardation than their White peers (National Alliance of Black School Educators & ILIAD Project, 2002). Specifically, a definite relationship exists between poverty and three other factors: ethnicity, gender, and mental retardation (Oswald et al., 2001). However, this relationship may be somewhat different from what one might initially suspect: The risk factors of poverty (limited access to health care, poor living conditions) do not entirely explain this disproportionate representation (Ford et al., 2002; Neal et al., 2003). Rather, "the increased rate of identification among students of color may be attributable to systemic bias" (Oswald et al., 2001, p. 361). Black students who live in a predominantly White neighborhood are more likely to be identified as having mental retardation than those who live in a neighborhood with more diversity. One conclusion is that students are more vulnerable to discrimination when they represent a minority. Many strategies can be undertaken to reduce mistakes in the identification process, including pre-referral intervention, appropriate and meaningful curricula, and instruction anchored in culturally relevant examples.


Many cases of mental retardation can be prevented by directly addressing the cause. According to The Are, because of advances in research over the last 30 years, many cases of mental retardation are prevented (The Are, 2005). For example, each year 9,000 cases of mental retardation are prevented via the measles and Hib vaccines. 1,250 cases via newborn screening for phenylketonuria (PKU) and congential hypothyroidism, and 1,000 cases via the anti-RH immune globulin. Even more cases are preventable. Most of these strategies (as seen in the table below) are simple and obvious, but the effects can be significant. For example, in the case of child abuse, teachers now have a legal (and, many believe, a moral) responsibility to report suspected cases so that further damage to the child might be avoided.

Education and access are at the heart of many prevention measures. For example, education about the prevention of HIV/AIDS can be effective with all adolescents, including those with mental retardation (Johnson, Johnson, & Jefferson-Aker, 2001). Public education programs can also help pregnant women understand the importance of staying healthy. Other prevention strategies involve testing the expectant mother, analyzing the risk factors of the family (genetic history of disabilities or various conditions), and taking action when necessary; screening infants; protecting children from disease through vaccinations; creating positive, nurturing, and rich home and school environments; and implementing safety measures. Note that not all of these strategies are biological or medical. It is important to look at all aspects of the child and the environment.

The importance of immunization programs to protect children and their mothers from disease cannot be overemphasized (The Arc, 2005; CDF, 2004). The incidence of disabilities, including mental retardation, has been greatly reduced by immunization against viruses such as rubella, meningitis, and measles. However, immunization is still not provided universally. Despite more federal and state programs to assist families in protecting their children, only some 78 percent of two-year-olds had received all recommended immunizations in 2002. Why is this so? Some families do not have access to immunizations because a health care facility is unavailable or is too far from home, or because the immunizations are too expensive. Some families ignore or are uninformed about the risks of skipping vaccinations, and other families avoid immunizations for religious reasons or believe that the risk of getting the disease from the vaccination itself is greater than the risk of being unprotected. As a result, easily preventable cases of mental retardation due to infection still occur.

People must not underestimate the importance of prenatal care. For example, FAS and FAE are 100 percent preventable (CDC, 2004b; Davis & Davis, 2003). Pregnant mothers who do not drink alcohol prevent this condition in their children! Staying healthy also means taking proper vitamins and eating well, and there are good examples of why this is essential. For example, folic acid reduces the incidence of neural tube defects. By eating citrus fruits and dark, leafy vegetables (or taking vitamin supplements), one receives the benefits of folic acid—a trace B vitamin that contributes to the prevention of conditions such as spina bifida and anencephaly. Here's proof that such prevention measures make a difference: In 1992 the U.S. Public Health Service recommended that all women thinking about becoming pregnant take folic acid daily, either through diet or supplements, and mandated that cereal be fortified with folic acid. Since then, the prevalence of spina bifida has dropped by 31 percent and that of anencephaly by 16 percent (CDC, 2004b). Think of the difference yet to be made if all potential moms ate well and planned ahead!

We also noted that prematurity (being born before 37 weeks of pregnancy) and low birth weight are risk factors for mental retardation and other disabilities. Unfortunately, relatively little is known about how to prevent many of these cases (Alexander & Slay, 2002). It is known that it is important for as many unborn babies as possible to reach full-term and that good prenatal care is an important part of making that happen.

Couples can take certain actions before the woman becomes pregnant to reduce the risk of biologically caused mental retardation. For example, gene therapy may become universally available to families who know they are at risk for having offspring with PKU (Eisensmith, Kuzmin, & Krougliak, 1999). Some couples have medical tests before deciding to conceive a child. These tests, combined with genetic counseling, help couples determine whether future children are at risk for certain causes of mental retardation. In one study, the majority of women who received genetic counseling either because of their age or because of an abnormal blood test indicated that they would avoid or terminate the pregnancy if a test was positive for a disability (Roberts, Stough, & Parrish, 2002). Tay-Sachs disease, for example, is a cause of mental retardation that can be predicted through genetic testing. Other couples take tests for defects after they find out that the woman is pregnant. These tests can determine, in utero, the presence of approximately 270 defects. It is possible that prenatal gene therapy, now in experimental phases, will one day correct such abnormalities before babies are born (Ye et al., 2001).

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