A syndrome beginning in infancy and characterised by a lack of
responsiveness to other people, gross impairment in verbal and
nonverbal communication skills, and bizarre responses to the
environment.
Autism is not a disease, but a developmental disorder of brain
function. People with classical autism show three types of symptoms:
impaired social interaction, problems with verbal and nonverbal
communication and imagination, and unusual or severely limited
activities and interests. Symptoms of autism usually appear during the
first three years of childhood and continue throughout life. Although
there is no cure, appropriate management may foster relatively normal
development and reduce undesirable behaviors. People with autism have a
normal life expectancy.
Autism affects an estimated 10 to 20 of every 10,000 people,
depending on the diagnostic criteria used. Most estimates that include
people with similar disorders are two to three times greater. Autism
strikes males about four times as often as females, and has been found
throughout the world in people of all racial and social backgrounds.
Autism varies a great deal in severity. The most severe cases are
marked by extremely repetitive, unusual, self-injurious, and aggressive
behavior. This behavior may persist over time and prove very difficult
to change, posing a tremendous challenge to those who must live with,
treat, and teach these individuals. The mildest forms of autism
resemble a personality disorder associated with a perceived learning
disability.
The hallmark feature of autism is impaired social interaction.
Children with autism may fail to respond to their names and often avoid
looking at other people. Such children often have difficulty
interpreting tone of voice or facial expressions and do not respond to
others' emotions or watch other people's faces for cues about
appropriate behavior. They appear unaware of others' feelings toward
them and of the negative impact of their behavior on other people.
Many children with autism engage in repetitive movements such as
rocking and hair twirling, or in self-injurious behavior such as biting
or head-banging. They also tend to start speaking later than other
children and may refer to themselves by name instead of "I" or "me."
Some speak in a sing-song voice about a narrow range of favorite
topics, with little regard for the interests of the person to whom they
are speaking.
People with autism often have abnormal responses to sounds, touch,
or other sensory stimulation. Many show reduced sensitivity to pain.
They also may be extraordinarily sensitive to other sensations. These
unusual sensitivities may contribute to behavioral symptoms such as
resistance to being cuddled.
Autism is classified as one of the pervasive developmental
disorders. Some doctors also use terms such as "emotionally disturbed"
to describe people with autism. Because it varies widely in its
severity and symptoms, autism may go unrecognized, especially in mildly
affected individuals or in those with multiple handicaps.
Researchers and therapists have developed several sets of diagnostic criteria for autism. Some frequently used criteria include:
- Absence or impairment of imaginative and social play.
- Impaired ability to make friends with peers.
- Impaired ability to initiate or sustain a conversation with others.
- Stereotyped, repetitive, or unusual use of language.
- Restricted patterns of interests that are abnormal in intensity or focus.
- Apparently inflexible adherence to specific routines or rituals.
- Preoccupation with parts of objects.
Since hearing problems can be confused with autism, children with
delayed speech development should always have their hearing checked.
Children sometimes have impaired hearing in addition to autism. About
half of people with autism score below 50 on IQ tests, 20 percent score
between 50 and 70, and 30 percent score higher than 70. However,
estimating IQ in young children with autism is often difficult because
problems with language and behavior can interfere with testing. A small
percentage of people with autism are savants. These people have limited
but extraordinary skills in areas like music, mathematics, drawing, or
visualization.
Autism has no single cause. Researchers believe several genes, as
well as environmental factors such as viruses or chemicals, contribute
to the disorder. Studies of people with autism have found abnormalities
in several regions of the brain, including the cerebellum, amygdala,
hippocampus, septum, and mamillary bodies. Neurons in these regions
appear smaller than normal and have stunted nerve fibers, which may
interfere with nerve signaling. These abnormalities suggest that autism
results from disruption of normal brain development early in fetal
development. While these findings are intriguing, they are preliminary
and require further study. The early belief that parental practices are
responsible for autism has now been disproved.
Some doctors speculate that autism may be the result of a specific
brain injury or brain abnormality that occurred during brain
development (before birth) or early in infancy. Others have found
evidence that the disorder is a result of abnormal levels of
neurotransmitters (chemicals that transmit messages between cells in
the brain and nerves), especially the neurotransmitters dopamine and
serotonin.
Recent studies strongly suggest that some people have a genetic
predisposition to autism. Scientists estimate that, in families with
one autistic child, the risk of having a second child with the disorder
is approximately five percent, or one in 20, which is greater than the
risk for the general population.
There is no cure for autism at present. Therapies, or interventions,
are designed to remedy specific symptoms in each individual. The
best-studied therapies include educational/behavioral and medical
interventions. Although these interventions do not cure autism, they
often bring about substantial improvement.
- Facts About Autism. NIH Publication No. 96-1877. National
Institute of Neurological Disorders and Stroke, National Institutes of
Health, Bethesda, Maryland 20892-2540
