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8.65: Mental Retardation

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  • There are three classification systems used when defining mental retardation criterion in North America, the DSM-IV-TR, AAMR, and the Educational System.

    DSM-IV-TR criteria

    • A. Significantly sub average intellectual functioning: an IQ of approximately 70 or below on an individually administered IQ test (for infants, a clinical judgment of significantly sub-average intellectual functioning).
    • B. Concurrent deficits or impairments in present adaptive functioning (i.e., the person’s effectiveness in meeting the standards expected for his or her age by his or her culture group) in at least two of the following areas: communication, self-care, home living, social/interpersonal skills, use of community resources, self-direction, functional academic skills, work, leisure, health, and safety.
    • C. The onset is prior to 18 years of age.
    • Code based on degree of severity reflecting level of intellectual impairment:
      • 317 Mild Mental Retardation: IQ level 50-55 to approximately 70 (accounts for 85% of retarded population). Mild Mental Retardation is roughly equivalent to what used to be referred to as the educational category of “educable.” This group constitutes the largest segment (about 85%) of those with the disorder. As a group, people with this level of Mental Retardation typically develop social and communication skills during the preschool years (ages 0-5 years), have minimal impairment in sensorimotor areas, and often are not distinguishable from children without Mental Retardation until a later age. By their late teens, they can acquire academic skills up to approximately the sixth-grade level. During their adult years, they usually achieve social and vocational skills adequate for minimum self-support, but may need supervision, guidance, and assistance, especially when under unusual social or economic stress. With appropriate supports, individuals with Mild Mental Retardation can usually live successfully in the community, either independently or in supervised settings.
      • 318.0 Moderate Mental Retardation: IQ level 35-40 to 50-55 (accounts for 10% of retarded population). Moderate Mental Retardation is roughly equivalent to what used to be referred to as the educational category of “trainable.” This outdated term should not be used because it wrongly implies that people with Moderate Mental Retardation cannot benefit from educational programs. This group constitutes about 10% of the entire population of people with Mental Retardation. Most of the individuals with this level of Mental Retardation acquire communication skills during early childhood years. They profit from vocational training and, with moderate supervision, can attend to their personal care. They can also benefit from training social and occupational skills but are unlikely to progress beyond the second-grade level in academic subjects. They may learn to travel independently in familiar places. During adolescence, their difficulties in recognizing social conventions may interfere with peer relationships. In their adult years, the majority are able to perform unskilled or semiskilled work under supervision in sheltered workshops or in the general workforce. They adapt well to life in the community, usually in supervised settings.
      • 318.1 Severe Mental Retardation: IQ level 20-25 to 35-40 (accounts for 3-4% of retarded population). The group with Severe Mental Retardation constitutes 3%-4%of individuals with Mental Retardation. During the early childhood years, they acquire little or no communication speech. During the school-age period, they may learn to talk and can be trained in elementary self-care skills. They profit to only a limited extent from instruction in pre-academic subjects, such as familiarity with the alphabet and simple counting, but can master skills such as learning slight reading of some “survival” words. In their adult years, they may be able to perform simple tasks in closely supervised settings. Most adapt well to life in the community, in group homes or with their families, unless they have an associated handicap that requires specialized nursing or other care.
      • 318.2 Profound Mental Retardation: IQ level below 20-25 (accounts for 1-2% of retarded population). The group with Profound Mental Retardation constitutes approximately 1%-2% of people with Mental Retardation. Most individuals with this diagnosis have an identified neurological condition that accounts for their Mental Retardation. During the early childhood years, they display considerable impairments in sensorimotor functioning. Optimal development may occur in a highly structured environment with constant aid and supervision and an individualized relationship with a caregiver. Motor development and self-care and communication skills may improve if appropriate training is provided. Some can perform simple tasks in closely supervised and sheltered settings.
      • 319 Mental Retardation, Severity Unspecified: when there is strong presumption of Mental Retardation but the person’s intelligence is untestable by standard tests. The diagnosis of Mental Retardation, Severity Unspecified, should be used when there is a strong presumption of Mental Retardation but the person cannot be successfully tested by standardized intelligence tests. This may be the case when children, adolescents, or adults are too impaired or uncooperative to be tested or, with infants, when there is a clinical judgment of significantly sub average intellectual functioning. The available tests (e.g., The Bayley Scales of Infant Development, Cattell Infant Intelligence Scales, and others) do not yield IQ values. In general, the younger the age, the more difficult it is to assess for the presence of Mental Retardation except in those with profound impairment. The Bayley Scales of Infant Development (BSID) measure the mental and motor development and test the behavior of infants from one to 42 months of age. The BSID are used to describe the current developmental functioning of infants and to assist in diagnosis and treatment planning for infants with developmental delays or disabilities. The test is intended to measure a child’s level of development in three domains: cognitive, motor, and behavioral.

    American Association of Mental Retardation

    The American Association on Mental Retardation is another one of the three classification systems currently used in North America. Instead of focusing on the severity of the disorder, AAMP focuses on how intense the intervention is (intermittent, limited, extensive, or pervasive). Another difference between the DSM-IV-TR and AAMP is that the AAMP does not view MR as a metal disorder (Axis II) or a medical disorder. However, both classification systems view MR as having limited intellectual and adaptive skills. The two also agree that the age of onset it prior to the age of 18, the IQ level should be 70 or below, and that you must meet criteria other than an IQ score. The most recent definition in AAMP focuses on considering ecological and multidimensional influences when you are developing interventions. The nine areas in which you must rate the intensity of intervention are: human development, education, home living, community living, employment, health and safety, behavior, social, and protection issues.

    Educational System

    The third classification system for defining mental retardation is the Educational System. In the educational system there has been many changes regarding the cutoff level for placement in the special education system. In the 1970s the IQ level designated for mental retardation was 85. It is difficult for the educational system to define mental retardation criterion by themselves because the special education system is funded by the state governments in which their criteria corresponds with the DSM-IV-TR and AAMP.

    Associated features

    There are no specific personality traits associated with Mental Retardation. Some individuals are passive, placid, and dependent, but others may be aggressive. Lack of communication skills may cause dispose them toward disruptive behaviors as a substitute for language. Developmental delays vary widely with the nature of mental retardation. For example, in some cases, incapacity is only limited to impaired academic performance, but all adaptive skills are adequate. Some have aggressive features with comorbid behavior problems. This problem would make adjustment difficult. Negative features include self-injurious behavior, aggression, stereotypical movements, communication problems, and overactivity. Mild cases of MR can function adequately at a slower pace when goals have been modified. Cognitive limitations tend to be less noticeable in a predictable and structured environment. Those with Mental Retardation have a prevalence of comorbid disorders that are much higher than the general population, although there is no evidence to suggest that the disorder will present itself differently than in someone without Mental Retardation. It is more difficult to diagnose comorbid mental disorders, though, because of their difficulty in communication to give an adequate history. The most commonly seen comorbid disorders are Attention-Deficit/Hyperactivity Disorder, Mood Disorders, Pervasive Developmental Disorders, Stereotypical Movement Disorder, and Mental Disorders Due to a General Medical Condition. One of the key defining features in making a diagnosis of MR is that in MR the person will commenstraut with expected IQ but have low academic achievement. There is, however, a significant discrepency between IQ and achievement. There are four levels of severity of MR based on the individuals level of functioning and associated expectations: mild, moderate, severe, and profound. Many have problems in central processing, or classification of stimuli through the use of memory. Memory is also difficult. They also have deficits in executive function, the decision-making element that controls reception, central processing, adn expression.

    Child vs. adult presentation

    Since one criteria is onset before 18 years of age, children are more likely to statistically have Mental Retardation. Children are at a higher risk for MR because most Mental Retardation comes from within the womb and birth, (infections, chromosomal abnormalities, environmental, metabolic, and nutritional), but Mental Retardation can occur in other ways. Adults can also be diagnosed with Mental Retardation. Adult MR can also come about from toxic exposure and trauma (most likely to the brain). There are also unexplained reasons; this particular reasoning is the largest one because there are so many cases of Mental Retardation that cannot be explained. (Mental Retardation, 1997).

    Gender and cultural differences in presentation

    Individualized testing are always required to make the diagnosis of Mental Retardation. Mental Retardation due to known biological factors is similar among children of upper and lower socioeconomic classes, except that certain etiological factors are linked to lower socioeconomic status. Some biological factors are irregular genes or genes that did not fuse together properly, an example being down syndrome (when there is the presents of an extra chromosome). In cases in which no specific biological causation can be identified, the Mental Retardation is usually milder and individuals from lower socioeconomic classes are overrepresented. There is no cultural differences in presentation of mental retardation. Mental Retardation is more common among males, with a male-to-female ratio of approximately 1.5:1. (Mental Retardation, 2009)


    Testing for MR has become increasingly improved over the years. New testing has come about biotechnological progress such as antenatal and neonatal screenings are some of these new types of testing. The real factor is that this new testing are not always available for all individuals. Also, these tests are at high risk and are still unsound for specific results. (Leonard & Wen, 2002) Mental retardation occurs about 2.5% to 3% of the total population. In most cases, it is a lifelong condition. Socioeconomic status & ethnicity plays a role in MR. MR tends to be more common among low SES and minority groups. Relationship between mild MR and parental SES and its highly correlated measure, parental IQ. A classic study by Reed & Reed (1965). Association of mild MR and race is more complicated. IQ couldn’t be used to put someone in special classes. Test bias, de-emphasis by schools of the importance of IQ in diagnostic decisions. A classic cases that describes the importance of IQ is the Larry P. v. Riles case in California and its effects.

    Developmental Theories

    Double ABCX Model is known as a crisis of raising a child with MR (x) is a function of child’s characteristics (A), family’s resources (B), and family’s perceptions (C). The concept of stress was first introduced into family studies by researcher’s examining impacts of the 1930s great depression. Hill (1949) ABCX Model, McCubbin and Patterson (1981) Double ABCX Model, and McCubbin and Figley (1938) stated that families generally operate on a predictable normal cycle, anticipating and accepting a sequence of events that will occur throughout the life-force. Below is a picture of the Double ABCX Model.



    There are a number of causes of mental retardation. The majority of causes come from Down Syndrome, Fetal Alcohol Syndrome, and Fragile X Syndrome.

    • Genetic causes occur when errors are made when genes combine. Chromosome errors result in Down Syndrome and Fragile X Syndrome. This is the most common cause of mental retardation.
    • Problems during pregnancy can also result in mental retardation. If the mother is using alcohol or drugs such as LSD, STP, marijuana, or alcohol, she may cause damage to the brain. Thalidomide has also been shown to cause Mental Retardation, and the effects of lead can also play a role. Other illness that the mother has during the pregnancy, such as rubella or German measles, syphilis, or toxoplasmosis can cause mental retardation. Also, if the brain is not formed properly during the growth of the baby, mental retardation can result.
    • Problems during birth can cause mental retardation as well, such as prematurity, the umbilical cord being around the neck, or the misuse of forceps.
    • After birth, children can develop mental retardation from diseases such as measles or whooping cough. Also, exposure to high amounts of mercury or lead can cause damage to the brain and nervous system.
    • Another cause is related to poverty and cultural deprivation. Children can become mentally retarded because of malnutrition, environmental hazards, and poor medical care due to poverty. Also, research has been shown that under-stimulation regarding culture can result in damage to the brain.
    • Disorders of metabolism can also lead to Mental Retardation, such as phenylketanuria, gelactosemia, and maternal malnutrition.

    Down Syndrome is one cause of mental retardation. It is caused by a chromosome abnormality in the 21st chromosome. The incidence of Down Syndrome increases the older the mother is. However Down Syndrome is not directly caused by something the mother does during pregnancy.They are at increased risk for diseases of the cardiovascular and respiratory systems, Alzheimer’s Disease, and hearing and vision loss. Individuals with down syndrome are usually characterized by moderate mental retardation, slowing rate of development, social strengths, and weaknesses in grammar and speech. People with Down Syndrome have developmental delays and physical attributes that distinguish the disorder, such as almond-shaped “puffy” eyes, straight hair, shortness, a small skull that is flat in the back, a simean crease across the palm, leathery texture to the palms and soles, a small mouth, a flat philtrum, and square hands and stubby fingers. However, some people with Down Syndrome do not have these physical characteristics that set them apart. Also, they developmental and cognitive delays vary from person to person. People with Down Syndrome have a shorter lifespan. However, recently the life expectancy for people with Down syndrome has increased. In 1929, their average lifespan was nine years, and now it is common for them to live to age fifty and above.

    Check out the link below to view the facial features of people who are diagnosed with Down Syndrome: Notice the almond shaped eyes, light-colored spots in their eyes, small flat noses, small ears, small mouth with protruding tongues, and round faces. There are many other features, these are just to name a few.

    Fragile X Syndrome is the most common cause of an inherited mental impairment. It can be passed on to children, even if there are no apparent symptoms of the disorder in the parents. People are carriers of a certain gene (FMR1) and not even know it. The only way to know this is through genetic counseling. The FMR1 gene mutates in the development of the child and that is how the child could get it. Normally, at least one parent has to be a carrier of the gene, because new mutations are rare. Individuals with fragile X usually have moderate mental retardation, strength in Gestalt reasoning, and weakness in sequential processing. They are also usually autistic and exhibit ADHD-like behaviors. People with fragile X syndrome have physical attributes that distinguish the disorder, such as a long narrow face, prominent ears, prominent jaw & forehead, high arched palate, flat feet, hyperextensible joints, and enlarged testicles in males.

    Males with fragile X syndrome and autism (FXS/autism) represent a distinct subgroup of males with FXS at risk for markedly poorer outcomes. Early identification and intervention can improve outcomes for males with autism spectrum disorder. Both social and repetitive behaviors distinguished males with FXS/autism, with repetitive behaviors playing a more prominent role than previously documented in the literature. Healthcare workers and early interventionists may be able to interview parents about a few key behaviors to determine if young child with FXS should be formally evaluated for autism. Evidence-based practices identified for children with autism spectrum disorder can be implemented as early as possible (Brock, & Hatton, 2010).


    A YouTube element has been excluded from this version of the text. You can view it online here:

    Williams Syndrome is a rare genetic condition (estimated to occur in 1/10,000 births) which causes medical and developmental problems. It is present at birth, and affects males and females equally. It can occur in all ethnic groups and has been identified in countries throughout the world. Individuals who are diagnosed with this disease have a small upturned nose, long philtrum (uppper lip length), wide mouth, full lips, small chin, and puffiness around the eyes. They have heart and blood vessel problems because they are born with small blood vessels, as well as feeding problems. The usually have good verbal and language skills. Individuals with this disease have high death rates.

    external image abc_gma_syndrome2_070719_mn.jpg

    Prader-Willi Syndrome (PWS) is an uncommon genetic disorder. It causes poor muscle tone, low levels of sex hormones and a constant feeling of hunger. The part of the brain that controls feelings of fullness or hunger does not work properly in people with PWS. They overeat, leading to obesity. Babies with PWS are usually floppy, with poor muscle tone, and have trouble sucking. Boys may have undescended testicles. Later, other signs appear. These include:

    • Short stature
    • Poor motor skills
    • Weight gain
    • Underdeveloped sex organs
    • Mild mental retardation and learning disabilities

    Fetal Alcohol Syndrome (FAS) is caused by drinking alcohol during pregnancy. The problems that arise from this often intensify when children grow up. There are many developmental delays that occur with FAS as well as physical attributes that are distinguishable.

    • Signs and Symptoms:

      • low birth weight
      • small head circumference
      • developmental delay
      • organ dysfunction
      • facial abnormalities, including smaller eye openings, flattened cheekbones, and indistinct philtrum (an underdeveloped groove between the nose and the upper lip)
      • epilepsy
      • failure to thrive
      • poor coordination/fine motor skills
      • poor socialization skills, such as difficulty building and maintaining friendships and relating to groups
      • lack of imagination or curiosity
      • learning difficulties, including poor memory, inability to understand concepts such as time and money, poor language comprehension, poor problem-solving skills
      • behavioral problems, including hyperactivity, inability to concentrate, social withdrawal, stubbornness, impulsiveness, and anxiety
    • Children can also be born with Fetal Alcohol Effects (FAE). This has the same symptoms of FAS but are less severe.

    Mental Retardation can be associated with mental disorders having the commonality of head trauma that can result in Mental Retardation and in personality change due to head trauma. The etiological factors are both biological and psychosocial. In approximately 30%-40% of individuals seen in clinical settings, no clear etiology for the Mental Retardation can be determined despite extensive evaluation efforts. Some of these predisposing factors are heredity, alterations of embryonic development, environmental influences, mental disorders, pregnancy and prenatal problems, and general medical conditions acquired in infancy or childhood.

    Empirically supported treatments

    Applied behavior analysis is a type of discipline that is applied in a genuine setting such as schools and clinics. This type of analysis deals with socially important issues such as learning disabilities and behavioral difficulties. (Hagopian & Boelter, 2005) Cognitive and adaptive functioning can also play a role in helping control problems faced with mental retardation.

    The most effective treatment are individualized educational and skill plans that are based on the child’s needs. The federal government mandates this and it as no extra cost to the family. A loving and supportive family is key to the treatment of mental retardation. Families can benefit from family therapy by learning to cope with the stress and other day-to-day activities involved with raising a child with mental retardation. Some children can go far in school while others cannot, it just depends on the severity of their retardation.

    Preventing mental retardation can be done in a few ways. Avoiding alcohol and drugs, eating a healthy diet, and taking prenatal vitamins during pregnancy all are proactive steps to be taken to help prevent mental retardation. Also, getting children vaccinated against diseases such as measles can be helpful as well.



    Organic MR Cultural-familal MR
    Definition Individual shows a clear organic cause of mental retardation Individual shows no obvious cause of retardation; sometimes another family member is also retarded
    Characteristics More prevalent at moderate; severe and profound levels of retardationEqual or near-equal rates across all ethnic and SES levelsMore often associated with other physical-disabilities More prevalent in mild mental retardationHigher rates within minority groups and low SES groupsFew associated physical or medical disabilities
    Causes Prenatal (genetic disorders, accidents in utero)Perinatal (prematurity, anoxia)Postnatal (head trauma, meningitis) Polygenic (i.e., parts of low IQ)Environmentally deprivedUndetected organic conditions
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