What is autism?
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 two to 10 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.
What are some common signs of autism?
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.
How is autism diagnosed?
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:1
- 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
Children with
some symptoms of autism, but not enough to
be diagnosed with the classical form of the
disorder, are often diagnosed with
pervasive developmental disorder - not
otherwise specified (PDD - NOS). The
term Asperger syndrome is sometimes
used to describe people with autistic
behavior but well-developed language skills.
Children who appear normal in their first
several years, then lose skills and begin
showing autistic behavior, may be diagnosed
with childhood disintegrative disorder (CDD).
Girls with Rett's syndrome, a
sex-linked genetic disorder characterized by
inadequate brain growth, seizures, and other
neurological problems, also may show
autistic behavior. PDD - NOS, Asperger
syndrome, CDD, and Rett's syndrome are
sometimes referred to as autism spectrum
disorders.
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. |
What causes autism?
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. Other studies suggest that
people with autism have abnormalities of
serotonin or other signaling molecules in
the brain. 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.
In a minority
of cases, disorders such as fragile X
syndrome, tuberous sclerosis, untreated
phenylketonuria (PKU), and congenital
rubella cause autistic behavior. Other
disorders, including Tourette syndrome,
learning disabilities, and attention deficit
disorder, often occur with autism but do not
cause it. For reasons that are still
unclear, about 20 to 30 percent of people
with autism also develop epilepsy by the
time they reach adulthood. While people with
schizophrenia may show some autistic-like
behavior, their symptoms usually do not
appear until the late teens or early
adulthood. Most people with schizophrenia
also have hallucinations and delusions,
which are not found in autism.
What role does genetics play?
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 (see "What is autism?").
Researchers are looking for clues about
which genes contribute to this increased
susceptibility. In some cases, parents and
other relatives of an autistic person show
mild social, communicative, or repetitive
behaviors that allow them to function
normally but appear linked to autism.
Evidence also suggests that some affective,
or emotional, disorders, such as manic
depression, occur more frequently than
average in families of people with autism.
Do symptoms of autism change over time?
Symptoms in
many children with autism improve with
intervention or as the children mature. Some
people with autism eventually lead normal or
near-normal lives. However, reports from
parents of children with autism indicate
that some children's language skills regress
early in life, usually before age three.
This regression often seems linked to
epilepsy or seizure-like brain activity.
Adolescence also worsens behavior problems
in some children with autism, who may become
depressed or increasingly unmanageable.
Parents should be ready to adjust treatment
for their child's changing needs.
How can autism be treated?
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.
Educational/behavioral
interventions: These
strategies emphasize highly structured and
often intensive skill-oriented training that
is tailored to the individual child.
Therapists work with children to help them
develop social and language skills. Because
children learn most effectively and rapidly
when very young, this type of therapy should
begin as early as possible. Recent evidence
suggests that early intervention has a good
chance of favorably influencing brain
development.
Medication:
Doctors may prescribe a variety of drugs
to reduce self-injurious behavior or other
troublesome symptoms of autism, as well as
associated conditions such as epilepsy and
attention disorders. Most of these drugs
affect levels of serotonin or other
signaling chemicals in the brain.
Many other
interventions are available, but few, if
any, scientific studies support their use.
These therapies remain controversial and may
or may not reduce a specific person's
symptoms. Parents should use caution before
subscribing to any particular treatment.
Counseling for the families of people with
autism also may assist them in coping with
the disorder.
Prepared by
Office of Scientific and Health Reports
National Institute of Neurological Disorders
and Stroke
National Institutes of Health
Bethesda, Maryland 20892-2540
NIH
Publication No. 96-1877
Original
Publication Date: August 1996
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