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General Information about MENTAL RETARDATION

 

INTRODUCTION TO MENTAL RETARDATION


What is mental retardation?

According to the new definition by the American Association on Mental Retardation (AAMR), an individual is considered to have mental retardation based on the following three criteria: intellectual functioning level (IQ) is below 70-75; significant limitations exist in two or more adaptive skill areas; and the condition is present from childhood (defined as age 18 or less) (AAMR, 1992).

People with mental retardation are those who develop at a below average rate and experience difficulty in learning and social adjustment. The regulations for the Individuals with Disabilities Education Act (IDEA) provide the following technical definition for mental retardation:

"Mental retardation means significantly subaverage general intellectual functioning existing concurrently with deficits in adaptive behavior and manifested during the developmental period, that adversely affects a child's educational performance."

"General intellectual functioning" is typically measured by an intelligence test. Persons with mental retardation usually score 70 or below on such tests. "Adaptive behavior" refers to a person's adjustment to everyday life. Difficulties may occur in learning, communication, social, academic, vocational, and independent living skills.

Mental retardation is not a disease, nor should it be confused with mental illness. Children with mental retardation become adults; they do not remain "eternal children." They do learn, but slowly, and with difficulty.

Probably the greatest number of children with mental retardation have chromosome abnormalities. Other biological factors include (but are not limited to): asphyxia (lack of oxygen); blood incompatibilities between the mother and fetus; and maternal infections, such as rubella or herpes. Certain drugs have also been linked to problems in fetal development.

What are the adaptive skills essential for daily functioning?

Adaptive skill areas are those daily living skills needed to live, work and play in the community. The new definition includes ten adaptive skills: communication, self-care, home living, social skills, leisure, health and safety, self-direction, functional academics, community use and work. Adaptive skills are assessed in the person's typical environment across all aspects of an individual's life. A person with limits in intellectual functioning who does not have limits in adaptive skill areas may not be diagnosed as having mental retardation.

How many people are affected by mental retardation?

Some studies suggest that approximately 1% of the general population has mental retardation (when both intelligence and adaptive behavior measures are used). According to data reported to the U.S. Department of Education by the states, in the 1998-99 school year, 610-445 students ages 6-21 were classified as having mental retardation and were provided special education and related services by the public schools. This figure does not include students reported as having multiple disabilities or those in non-categorical special education pre-school programs who may also have mental retardation.

Various studies have been conducted in local communities to determine the prevalence of mental retardation. The Arc reviewed many of these prevalence studies in the early 1980s and concluded that 2.5 to 3 percent of the general population has mental retardation (The Arc, 1982). A recent review of prevalence studies generally confirms this distribution (Fryers, 1993).

Based on the 1990 census, an estimated 6.2 to 7.5 million people have mental retardation. Mental retardation is 12 times more common than cerebral palsy and 30 times more prevalent than neural tube defects such as spina bifida. It affects 100 times as many people as total blindness (Batshaw & Perret, 1992).

Mental retardation cuts across the lines of racial, ethnic, educational, social and economic backgrounds. It can occur in any family. One out of ten American families is directly affected by mental retardation.

How does mental retardation affect individuals?

The effects of mental retardation vary considerably among people, just as the range of abilities varies considerably among people who do not have mental retardation. About 87 percent will be mildly affected and will be only a little slower than average in learning new information and skills. As children, their mental retardation is not readily apparent and may not be identified until they enter school. As adults, many will be able to lead independent lives in the community and will no longer be viewed as having mental retardation.

The remaining 13 percent of people with mental retardation, those with IQs under 50, will have serious limitations in functioning. However, with early intervention, a functional education and appropriate supports as an adult, all can lead satisfying lives in the community.

AAMR's new definition no longer labels individuals according to the categories of mild, moderate, severe and profound mental retardation based on IQ level. Instead, it looks at the intensity and pattern of changing supports needed by an individual over a lifetime.

How is mental retardation diagnosed?

The AAMR process for diagnosing and classifying a person as having mental retardation contains three steps and describes the system of supports a person needs to overcome limits in adaptive skills.

The first step in diagnosis is to have a qualified person give one or more standardized intelligence tests and a standardized adaptive skills test, on an individual basis.

The second step is to describe the person's strengths and weaknesses across four dimensions. The four dimensions are:

1. Intellectual and adaptive behavior skills

2. Psychological/emotional considerations

3. Physical/health/etiological considerations

4. Environmental considerations

Strengths and weaknesses may be determined by formal testing, observations, interviewing key people in the individual's life, interviewing the individual, interacting with the person in his or her daily life or a combination of these approaches.

The third step requires an interdisciplinary team to determine needed supports across the four dimensions. Each support identified is assigned one of four levels of intensity - intermittent, limited, extensive, pervasive.

Intermittent support refers to support on an "as needed basis." An example would be support that is needed in order for a person to find a new job in the event of a job loss. Intermittent support may be needed occasionally by an individual over the lifespan, but not on a continuous daily basis.

Limited support may occur over a limited time span such as during transition from school to work or in time-limited job training. This type of support has a limit on the time that is needed to provide appropriate support for an individual.

Extensive support in a life area is assistance that an individual needs on a daily basis that is not limited by time. This may involve support in the home and/or support in work. Intermittent, limited and extensive supports may not be needed in all life areas for an individual.

Pervasive support refers to constant support across environments and life areas and may include life-sustaining measures. A person requiring pervasive support will need assistance on a daily basis across all life areas.

CHARACTERISTICS

Many authorities agree that people with mental retardation develop in the same way as people without mental retardation, but at a slower rate. Others suggest that persons with mental retardation have difficulties in particular areas of basic thinking and learning such as attention, perception, or memory. Depending on the extent of the impairment -- mild, moderate, severe, or profound -- individuals with mental retardation will develop differently in academic, social, and vocational skills.

What does the term "mental age" mean when used to describe the person's functioning?

The term mental age is used in intelligence testing. It means that the individual received the same number of correct responses on a standardized IQ test as the average person of that age in the sample population.

Saying that an older person with mental retardation is like a person of a younger age or has the "mind" or "understanding" of a younger person is incorrect usage of the term. The mental age only refers to the intelligence test score. It does not describe the level and nature of the person's experience and functioning in aspects of community life.


What are the causes of mental retardation?

Mental retardation can be caused by any condition which impairs development of the brain before birth, during birth or in the childhood years. Several hundred causes have been discovered, but in about one-third of the people affected, the cause remains unknown. The three major known causes of mental retardation are Down syndrome, fetal alcohol syndrome and fragile X.


The causes can be categorized as follows:

- Genetic conditions -- These result from abnormality of genes inherited 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. Inborn errors of metabolism which may produce mental retardation, such as PKU (phenylketonuria), fall in this category. Chromosomal abnormalities have likewise been related to some forms of mental retardation, such as Down syndrome and fragile X syndrome.

- Problems during pregnancy -- Use of alcohol or drugs by the pregnant mother can cause mental retardation. Malnutrition, rubella, glandular disorders and diabetes, cytomegalovirus, and many other illnesses of the mother during pregnancy may result in a child being born with mental retardation. Physical malformations of the brain and HIV infection originating in prenatal life may also result in mental retardation.

- Problems at birth -- Although any birth condition of unusual stress may injure the infant's brain, prematurity and low birth weight predict serious problems more often than any other conditions.

- Problems after birth -- Childhood diseases such as whooping cough, chicken pox, measles, and Hib disease which may lead to meningitis and encephalitis can damage the brain, as can accidents such as a blow to the head or near drowning. Substances such as lead and mercury can cause irreparable damage to the brain and nervous system.

- Poverty and cultural deprivation -- Children in poor families may become mentally retarded because of malnutrition, disease-producing conditions, inadequate medical care and environmental health. hazards. Also, children in disadvantaged areas may be deprived of many common cultural and day-to-day experiences provided to other youngsters. Research suggests that such under-stimulation can result in irreversible damage and can serve as a cause of mental retardation.

Can mental retardation be prevented?

During the past 30 years, significant advances in research have prevented many cases of mental retardation. For example, every year in the United States, we prevent:

- 250 cases of mental retardation due to phenylketonuria (PKU) by newborn screening and dietary treatment;

- 1,000 cases of mental retardation due to congenital hypothyroidism thanks to newborn screening and thyroid hormone replacement therapy,

- 2,000 cases of mental retardation or deafness by use of Rhogam to prevent Rh disease and severe jaundice in newborn infants;

- 3,000 cases of mental retardation due to measles encephalitis thanks to measles vaccine; and

- untold numbers of cases of mental retardation caused by rubella during pregnancy thanks to rubella vaccine (Alexander, 1991).

In addition, with the new vaccine against Hib disease, 3,000 to 4,000 cases of mental retardation can now be prevented.

New attempts at treatment of a variety of causes are being developed. There are now improved ways to manage head trauma, asphyxia (lack of oxygen) and infectious diseases to reduce their adverse effects on the brain. Early intervention programs with high-risk infants and children have shown remarkable results in reducing the predicted incidence of subnormal intellectual functioning.

Finally, early comprehensive prenatal care and preventive measures prior to and during pregnancy increase a woman's chances of preventing mental retardation.

EDUCATIONAL IMPLICATIONS

Persons with mental retardation have the capacity to learn, to develop, and to grow. The great majority of these citizens can become productive and full participants in society.

Appropriate educational services that begin in infancy and continue throughout the developmental period and beyond will enable children with mental retardation to develop to their fullest potential.

As with all education, modifying instruction to meet individual needs is the starting point for successful learning. Throughout their child's education, parents should be an integral part of the planning and teaching team.

In teaching persons with mental retardation, it is important to:

  • •Use concrete materials that are interesting, age-appropriate, and relevant to the students;
  • •Present information and instructions in small, sequential steps and review each step frequently;
  • •Provide prompt and consistent feedback;
  • •Teach these children, whenever possible, in the same school they would attend if they did not have mental retardation;
  • •Teach tasks or skills that students will use frequently in such a way that students can apply the tasks or skills in settings outside of school; and
  • •Remember that tasks that many people learn without instruction may need to be structured, or broken down into small steps or segments, with each step being carefully taught.

Children and adults with mental retardation need the same basic services that all people need for normal development. These include education, vocational preparation, health services, recreational opportunities, and many more. In addition, many persons with mental retardation need specialized services for special needs. Such services include diagnostic and evaluation centers; special early education opportunities, beginning with infant stimulation programs and continuing through preschool; and educational programs that include age-appropriate activities, functional academics, transition training, and opportunities for independent living and competitive employment to the maximum extent possible.

 This information is in the public domain unless otherwise indicated. Readers are encouraged to copy and share it, but please credit the National Information Center for Children and Youth with Disabilities (NICHCY).

Revised FEB 09