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Terms and Definitions

Below are some common terms and definitions that may help in understanding how we help those with intellectual disabilities.

People with intellectual disabilities generally have a mental capability which affects their ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly, and learn from experience. Studies show that somewhere between 1% and 3% of Americans have intellectual disabilities. There are many causes of intellectual disabilities that include physical, genetic and/or social factors. The most common syndromes associated with intellectual disabilities are autism, Down syndrome, Fragile X syndrome and Fetal Alcohol Spectrum Disorder (FASD).

People with mental retardation have differing abilities to learn and sometimes have difficulty applying what they have learned. An individual is considered to have mental retardation based on the following three criteria: intellectual function level (IQ) is below 70-75;significant limitations exist in two or more adaptive skill areas which are needed to live, work and play in the community and include communication, self-care, home living, social skills, leisure, health and safety, self-direction, and functional academics (reading, writing, basic math), and condition is present from childhood (defined as age 18 or less). Mental retardation can result from a variety of factors, including premature birth, genetic abnormalities, malnutrition, exposure to toxic agents and social deprivation. Through education and training, most people with mental retardation can learn to be self-sufficient. Assistance usually includes diagnosis and help early in life (including early intervention service coordination), family counseling and training, education, job training and residential services.

Down syndrome

is usually identified at birth or shortly thereafter. Initially the diagnosis is based on physical characteristics that are commonly seen in babies with Down syndrome. These include low muscle tone, a single crease across the palm of the hand, a slightly flattened facial profile and an upward slant to the eyes. The diagnosis must be confirmed by a chromosome study (karyotype) which identifies an extra copy of Chromosome 21. A karyotype provides a visual display of the chromosomes grouped by their size, number and shape. Chromosomes may be studied by examining blood or tissue cells.

Cerebral palsy

is the result of injury to the central nervous system which may occur before, during or anytime after birth and causes limited or abnormal functioning in the parts of the brain that control movement. People with cerebral palsy primarily have difficulty with muscular coordination. They may also have seizures or be unable to see, speak, hear or learn. Severe speech problems are common, sometimes leading others to make the mistake of thinking that people with cerebral palsy have mental retardation. This is often not true. Treatments for cerebral palsy include physical, occupational and speech/language therapy by skilled professionals. In-home and out-of-home residential services are also available.


(seizure disorder) applies to numerous nervous system disorders that result in abnormal electrical discharges of brain cells. This produces seizures that may cause convulsive movements, or partial or total loss of consciousness. Only a small percentage of people with epilepsy also have mental retardation.

Seizures can usually be controlled or prevented by the use of medicine. As a result, most people with epilepsy lead normal lives. When medication is not effective, specialized medical services, vocational programs as well as in-home and out-of-home residential services are available.


is a developmental disorder that limits learning and slows intellectual development. While autism’s cause is still unknown, most researchers believe it has a biological basis which is probably genetic. People with autism have great difficulty relating and responding to others, events or objects. People who have mild autism have limited interests. They may demonstrate some repetitive actions and a marked lack of sensitivity to other people. People who have more severe autism have difficulty listening to and communicating with others. Their interactions with people can be confusing or uncertain at best. They may have multiple, repetitive behaviors, for example, rocking and unusual hand movements, and can be highly resistant to change. It often is possible to diagnose autism before someone is two years old. When a child fails to develop language abilities or shows a lack of desire to be around other people, professionals generally recommend clinical examinations that can uncover autism. Early diagnosis is important so that care and treatments, such as parent training, highly structured recreation programs, specialized education, residential services and training in daily living and social skills can be used to improve each child’s chances for development.

Neurological impairments

are a group of disabilities including disorders of the brain and central nervous system that generally begin during childhood or adolescence. These impairments considerably limit a person’s development, understanding, memory, attention span, fine muscle control, use of language, or ability to adjust to new situations.

People with neurological impairments may experience a variety of learning difficulties or social behavior problems. They may also have special care needs because of problems in muscle control. While neurological impairments can be difficult to diagnose and to treat, most people learn to compensate for these disabilities and do very well in life.

View our Frequently Asked Question’s for more information.