2001 Developmental Disabilities Assessment





Autism Spectrum Disorder
Cerebral Palsy
Musculo-skeletal Disorders
Neuromuscular Disorders
Traumatic Brain Injury



In Texas, mental retardation (MR) is legally defined as a condition that appears before age 18 in which intelligence is significantly below average, and personal care and social behaviors do not meet what is expected for the person's age and culture. It occurs during the developmental phase of life and is classified as one of the many developmental disabilities. An individual is considered to have mental retardation based on the following three criteria (Texas Department of Mental Health Mental Retardation [TDMHMR], 1994):

  • Intellectual functioning level (IQ) is below 70.
  • Significant limitations exist in two or more adaptive skill areas (daily living skills needed to live, work, and play in the community).
  • The condition is present from childhood.

The effects of mental retardation vary considerably among people. About 87 percent of people with mental retardation will be mildly affected (Chart 1), and are slower than average in learning new skills and information. The remaining 13 percent of people with mental retardation will have serious limitations in functioning and will require a significant amount of lifelong support in living, working, and playing in their communities (The Arc, 2000).

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Developmental disabilities (DD) occur in men and women of all ages, races, cultures and economic conditions. The causes vary and may include:

  • genetic anomalies
  • environmental factors
  • problems during pregnancy, at delivery, and after birth.

The Texas Planning Council for Developmental Disabilities (1996) describes developmental disabilities as severe, chronic, mental and/or physical conditions, that occur before the age of 22. Examples include:

mental retardation
cerebral palsy epilepsy
deafness chronic mental illness
various birth defects blindness

Developmental disabilities are also defined as lifelong conditions which limit a person's participation in three or more of the following major life activities (U.S. Department of Health and Human Services (USDHHS, 2001):

self care
language learning
self-direction independent living
economic self-sufficiency  

The term developmental disability is also applied to infants and young children, ages birth to 5 years, who have substantial developmental delays or specific conditions that will probably result in developmental disabilities without early childhood intervention.

The national estimate is that between 25 to 40 percent of the workforce may have special learning needs. The term "special learning needs" is also used globally to describe people with a range of learning disabilities. The range includes those with average or above-average intelligence (usually difficulties in the acquisition and use of listening, speaking, reading, writing, reasoning, mathematical abilities or social skills), mild mental retardation, slow learning, below-average IQ, or low basic skills (USDHHS, 2001).

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Autism Spectrum Disorder

Autism Spectrum Disorder (ASD), a Pervasive Developmental Disorder (PDD), is another common, but complex, developmental disability (Autism Society of America [ASA], 2000). Following are some facts about autism (The Paula and Anthony Rich Center for the Study and Treatment of Autism [PARCSTA], (2001):

Autism typically appears during the first three years of life and impacts the normal development of the brain in the areas of social interaction and communication skills. Children and adults with autism typically have difficulties in talking, playing with other children, and relating to others - even their family members.

The Paula and Anthony Rich Center for the Study and Treatment of Autism

  • Mental retardation and autism often co-exist.
  • It is estimated that between 75 percent and 80 percent of people with autism may function with or have some degree of mental retardation.
  • Autism typically appears during the first three years of life and impacts the normal development of the brain in the areas of social interaction and communication skills.
  • Children and adults with autism typically have difficulties in talking, playing with other children, and relating to others - even their family members.
  • For some persons with ASD, aggressive or self-injurious behavior may be present.
  • Autism is four times more prevalent in boys than girls. Family income, lifestyle, and educational levels do not affect the chance that it will occur (ASA, 2000).
  • People with autism tend to experience peaks and valleys of strengths and weaknesses, a characteristic which may distinguish them overall from people with mental retardation who generally appear to have a consistent developmental level in most of their personal skills and traits (PARCSTA, 2001).
  • The estimated number of persons in Travis County with ASD is between 1,625 and 3,249.1

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Cerebral Palsy

Cerebral palsy is a developmental disability that is primarily characterized by an inability to control motor function– specifically muscle control and coordination. It is caused by damage to one of more parts of the brain and usually occurs in the womb, during or shortly after birth, or during infancy. Depending on which areas of the brain are affected, people may experience the following (United Cerebral Palsy Associations [UCPA], 1996):

muscle tightness or spasm
involuntary movement
disturbance in gait impaired sight, hearing or speech
seizures mental retardation

It is estimated that some 500,000 children and adults in the United States manifest one or more symptoms of cerebral palsy. Approximately 5,000 infants are diagnosed with the condition each year. Prevalence of cerebral palsy is 1 in 230. The population of people with cerebral palsy in Travis County is estimated to be between 3,532 and 13,000. The lower estimate is based on prevalence data of 1 in 230, and the larger number includes estimates of unreported cases. The increase number of unreported cases is attributed to the fact that Austin attracts populations needing services from the surrounding area, has community resources, and the Austin State School is located nearby. Cerebral palsy and mental retardation may occur simultaneously and with other disabilities (UCPA, 1996).

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Epilepsy is a developmental condition that is diagnosed as a result of recurrent seizures. It may be present at any life stage and can also occur in people over 65 years of age who have a history of stroke, heart disease, or Alzheimer's disease. "Epilepsy is a chronic medical condition produced by temporary changes in the electrical functions of the brain causing seizures which affect awareness, movement, or sensation" (Epilepsy Foundation, 2001). Some facts are:

  • Twenty percent of all cases start before five years of age and fifty percent develop before age twenty-five (Cybear, 2001).
  • There are more than twenty different seizure disorders. A seizure can be defined as a brief and temporary disturbance within the electrical system of the brain, which affects one or several regions of the brain (Cybear, 2001).
  • In the majority of epilepsy cases (70%), there is no known cause. In the remaining cases (30%), the causes include: head injury, birth trauma, poisoning, infection, brain tumors, heredity, and maternal illness during pregnancy (Cybear, 2001).
  • The prevalence rate is 1.8 percent of the population or approximately 14,621 people in Travis County.

It is estimated that 2.3 million people in the United States have epilepsy, with about 181,000 new cases diagnosed each year (Epilepsy USA, 2001, July). Epilepsy may occur simultaneously with mental retardation and other disabilities. Seizures that cannot be controlled with medication can cause further damage to the brain.

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Musculo-skeletal Disorders

Musculo-skeletal Disorders, although they do not directly result in mental retardation, do cause developmental delays, which may include but are not limited to (S. Miller, personal communication, May 2001):

Muscular Dystrophy
Juvenile Arthritis
Peripheral nerve injuries Traumatic spinal cord injuries
Guillian Barre´ Syndrome (transient paralysis due to damaged nerve cells) Poliomyelitis (Polio)
Amputations (congenital or traumatic) Congenital heart defects
Juvenile Diabetes  

As maturation occurs, children with any of these medical conditions may be unable to interact with their environments on a motor or sensory level due to the physical limitations of their disabilities. This inability to relate and develop successful learning patterns leads to delays that can effect physical, emotional, and social development. Muscular Dystrophy and Juvenile Arthritis are more progressive in nature and may profoundly affect normal development (S. Miller, personal communication, May 2001).

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Neuromuscular Disorders

Neuromuscular Disorders affecting the brain that produce cognitive deficits or mental retardation include (S. Miller, personal communication, May 2001):

  • Adrenaleukodystrophies (nervous system disorders that result in progressive deterioration of sensory, neural and muscular development and function) which are progressive;
  • Traumatic head injuries;
  • Brain injury chemically induced either before birth (mother exposed to a toxic chemical) or after birth (child's exposure in gestation);
  • Hydrocephalus (increased pressure on brain due to impaired circulation of cerebrospinal fluid); and,
  • Spina Bifida (incomplete development of the spinal cord and some brain areas).

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Traumatic Brain Injury

Traumatic Brain Injury, which may occur in children as well as adults, often occurs from traumatic occurrences (before and after birth). These injuries can cause an interruption in cognitive/motor communication functions, which can lead to developmental delay(s) in children (S. Miller, personal communication, May 2001).

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Positive social and interpersonal relationships are important for a rich and fulfilling life and to maintain mental health, which is an essential component in quality of life. The goal is for all people, including those with mental retardation/developmental disabilities to have positive social and interpersonal relationships. People with mental retardation can and do experience the full range of mental disorders similar to the general population.2   While there is no unique psychiatric syndrome associated with mental retardation, persons with mental retardation may be considered to be more susceptible than others to mental illness. The reasons for this susceptibility are multifaceted and include biological, psychosocial and developmental factors (Reiss, 1993).

This prevalence information translates into a conservative estimate of 1,786 Travis County residents with mental retardation experiencing some form of mental illness.

According to the National Association on Mental Illness (NAMI), mental illnesses are disorders of the brain that disrupt a person's thinking, feeling, moods, and ability to relate to others. Researchers generally believe that there are both biological and psychological risk factors. Some disorders may be caused or contributed to by abnormalities in the biochemistry and structure of the brain.

Inherited factors may play a role. An individual's life experiences and environment may also contribute to the severity of some mental illnesses. Some of the most common types of mental illnesses seen in people with mental retardation include major depression, bipolar disorder, anxiety disorders, personality disorders, schizophrenia and other psychotic disorders, and phobias (NAMI, 2001).

The incidence and prevalence of mental illness among people with mental retardation varies considerably depending upon age, type of mental illness, level of mental retardation and factors and methodology used in research. A report was produced that noted the following information among individuals with mental retardation and mental illness (USDHHS, 2001):

  • Ten to forty percent of persons dually diagnosed are reportedly served in specialized programs by community agencies.
  • Lower rates of 10 to 20 percent of persons dually diagnosed have been reported.
  • Conduct and behavioral problems are seen in about one in five people with mental retardation in the community.
  • The rate for mood disorders is estimated to be 3 to 6 percent of the general population of persons with mental retardation.
  • Dually diagnosed prevalence rates are higher for adults than for children under the age of 10.
  • Higher rates of mental illness are reported for individuals with mild and moderate versus severe and profound mental retardation, a difference that may be associated with the disparity in ability to report symptoms and participate in traditional diagnostic assessments.
  • Prevalence data suggests that mental illness occurs within the population of people with mental retardation in equal proportions for males and females, and for those of different racial and ethnic backgrounds.
  • Based on their information, a conservative estimate of 1,786 Travis County residents with mental retardation are experiencing some form of mental illness.

People with dual diagnoses, such as the coexistence of mental retardation and mental illness, may often be seen as adults with failed employment histories who reside in homeless shelters and/or within the criminal justice system. Individuals with dual diagnoses have complex needs and are often unable to access the services they need due to insufficient resources (O. Seay, personal communication, July, 2001).

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Assessment Home

1. Tim Cole, President of the Autism Society of Greater Austin, a local chapter of the Autism Society of America, conservatively calculates that 1,400 [new Census 2000 data indicates this number should be between 1,625 and 3,249] people in Travis County have ASD (R. Schleiss, personal communication, June 2001). The National Institute bases this estimate on the incident rates cited for Health (NIH) and Centers for Disease Control (CDC), which report ranges from 1 in 250 people to 1 in 500 people.

2. For more information on mental illness, see the CAN Assessment: Prescription For Wellness.