Autism Overview

What is autism?
What are some common signs of autism?
What are the symptoms of autism?
How is autism diagnosed?
What causes autism?
What role does inheritance play?

What is autism?

Autism (sometimes called “classical autism”) is the most common condition in a group of developmental disorders known as the autism spectrum disorders (ASDs). Autism is characterized by impaired social interaction, problems with verbal and nonverbal communication, and unusual, repetitive, or severely limited activities and interests.

Autistic disorder is the most commonly known type of ASD, but there are others, including pervasive developmental disorder-not otherwise specified (PDD-NOS) and Asperger syndrome. These three conditions all have some of the same symptoms, but they differ in terms of when the symptoms start, how fast they appear, how severe they are, and their exact nature. These three conditions, along with Rett syndrome and childhood disintegrative disorder, make up the broad diagnosis category of pervasive developmental disorders.
Date: June27, 2006 Content source: National Center on Birth Defects and Developmental Disabilities

Experts estimate that three to six children out of every 1,000 will have autism. Males are four times more likely to have autism than females.

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What are some common signs of autism?

There are three distinctive behaviors that characterize autism. Autistic children have difficulties with social interaction, problems with verbal and nonverbal communication, and repetitive behaviors or narrow, obsessive interests. These behaviors can range in impact from mild to disabling. The hallmark feature of autism is impaired social interaction. Parents are usually the first to notice symptoms of autism in their child. As early as infancy, a baby with autism may be unresponsive to people or focus intently on one item to the exclusion of others for long periods of time. A child with autism may appear to develop normally and then withdraw and become indifferent to social engagement.

Children with autism may fail to respond to their name and often avoid eye contact with other people. They have difficulty interpreting what others are thinking or feeling because they can’t understand social cues, such as tone of voice or facial expressions, and don’t watch other people’s faces for clues about appropriate behavior. They often lack empathy and engage in repetitive movements such as rocking and twirling, or in self-abusive 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.” Children with autism don’t know how to play interactively with other children. 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. Many children with autism have a reduced sensitivity to pain, but are abnormally sensitive to sound, touch, or other sensory stimulation. These unusual reactions may contribute to behavioral symptoms such as a resistance to being cuddled or hugged.

Children with autism appear to have a higher than normal risk for certain co-existing conditions, including fragile X syndrome (which causes mental retardation), tuberous sclerosis (in which tumors grow on the brain), epileptic seizures, Tourette syndrome, learning disabilities, and attention deficit disorder. For reasons that are still unclear, about 20 to 30 percent of children with autism 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.

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What are the symptoms of autism?

As the name “autism spectrum disorder” implies, ASDs cover a wide range of behaviors and abilities. People who have ASDs, like all people, differ greatly in the way they act and what they can do. No two people with ASDs will have the same symptoms. A symptom might be mild in one person and severe in another person. Types of problems and behaviors a child or adult with an ASD might have include the following:

  • Social skills: People with ASDs might not interact with others the way most people do, or they might not be interested in other people at all. People with ASD might not make eye contact and may just want to be alone. They might have trouble understanding other people’s feelings or talking about their own feelings. Children with ASD might not like to be held or cuddled, or might cuddle only when they want to. Some people with ASD might not seem to notice when other people try to talk to them. Others might be very interested in people, but not know how to talk, play, or relate to them.
  • Speech, language, and communication: About 40% of children with ASD do not talk at all. Others have echolalia, which is when they repeat back something that was said to them. The repeated words might be said right away or at a later time. For example, if you ask someone with ASD, “Do you want some juice?” he or she will repeat “Do you want some juice?” instead of answering your question. Or a person might repeat a television ad heard sometime in the past. People with ASD might not understand gestures such as waving goodbye. They might say “I” when they mean “you”, or vice versa. Their voices might sound flat and it might seem like they cannot control how loudly or softly they talk. People with ASD might stand too close to the people they are talking to, or might stick with one topic of conversation for too long. Some people with ASD can speak well and know a lot of words, but have a hard time listening to what other people say. They might talk a lot about something they really like, rather than have a back-and-forth conversation with someone.
  • Repeated behaviors and routines: People with ASD might repeat actions over and over again. They might want to have routines where things stay the same so they know what to expect. They might have trouble if family routines change. For example, if a child is used to washing his or her face before dressing for bed, he or she might become very upset if asked to change the order and dress first and then wash.

Children with ASD develop differently from other children. Children without ASD develop at about the same rate in areas of development such as motor, language, cognitive, and social skills. Children with ASD develop at different rates in different areas of growth. They might have large delays in language, social, and cognitive skills, while their motor skills might be about the same as other children their age. They might be very good at things like putting puzzles together or solving computer problems, but not very good at some things most people think are easy, like talking or making friends. Children with ASD might also learn a hard skill before they learn an easy one. For example, a child might be able to read long words, but not be able to tell you what sound a “b” makes. A child might also learn a skill and then lose it. For example, a child may be able to say many words, but later stop talking altogether.

Sources: 
Mauk JE, Reber M, Batshaw ML. Autism and other pervasive developmental disorders (4th edition). In: ML Batshaw, editor. Children with disabilities. Baltimore: Paul H. Brookes; 1997.
Powers MD. What is autism? In: MD Powers, editor. Children with autism: a parents’ guide, 2nd edition. Bethesda, MD: Woodbine House; 2000. pp. 1-44.


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How is autism diagnosed?

Autism diagnosis varies widely in its severity and symptoms and may go unrecognized, especially in mildly affected children or when it is masked by more debilitating handicaps. Doctors rely on a core group of behaviors to alert them to the possibility of a diagnosis of autism. These behaviors are:

  • impaired ability to initiate or sustain a conversation with others
  • absence or impairment of imaginative and social play
  • stereotyped, repetitive, or unusual use of language
  • restricted patterns of interest that are abnormal in intensity or focus
  • preoccupation with certain objects or subjects
  • inflexible adherence to specific routines or rituals

Doctors will often use a questionnaire or other screening instrument to gather information about a child’s development and behavior. Some screening instruments rely solely on parent observations; others rely on a combination of parent and doctor observations. If screening instruments indicate the possibility of autism, doctors will ask for a more comprehensive evaluation. Since autism is a complex disorder, a comprehensive evaluation requires a multidisciplinary team including a psychologist, neurologist, psychiatrist, speech therapist, and other professionals who diagnose children with ASD. The team members will conduct a thorough neurological assessment and in-depth cognitive and language testing. Because hearing problems can cause behaviors that could be mistaken for autism, children with delayed speech development should also have their hearing tested. After a thorough evaluation, the team usually meets with parents to explain the results of the evaluation and present the diagnosis.

Children with some symptoms of autism, but not enough to be diagnosed with classical autism, are often diagnosed with PDD-NOS. Children with autistic behaviors but well-developed language skills are often diagnosed with Asperger syndrome. Children who develop normally and then suddenly deteriorate between the ages of 3 to 10 years and show marked autistic behaviors may be diagnosed with childhood disintegrative disorder. Girls with autistic symptoms may be suffering from Rett syndrome, a sex-linked genetic disorder characterized by social withdrawal, regressed language skills, and hand wringing.  Click here, for more information on Autism Treatment.

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What causes autism?

We have learned a lot about the symptoms of ASDs and have improved efforts to track the disorders, but we still don’t know a lot about the cause of Autism. Scientists think that both genes and the environment play a role, and there might be many causes that lead to ASDs.

Family studies have been most helpful in understanding how genes contribute to autism. Studies have shown that among identical twins, if one child has autism, then the other will be affected about 75% of the time. In non-identical twins, if one child has autism, then the other has it about 3% of the time. Also, parents who have a child with an ASD have a 2%–8% chance of having a second child who is also affected.

For most people with ASDs, the cause is not known. But ASDs tend to occur more often than expected among people who have certain other medical conditions, including Fragile X syndrome, tuberous sclerosis, congenital rubella syndrome, and untreated phenylketonuria (PKU). Some harmful drugs taken during pregnancy also have been linked with a higher risk of autism, specifically, the prescription drug thalidomide.

CDC’s Centers for Autism and Developmental Disabilities Surveillance and Epidemiology (CADDRE) are working together on a large, population-based study to better understand the possible risk factors for and causes of autism. Called the Study to Explore Early Development (SEED), this project will help answer the many questions needed to find the causes of autism and—if possible—come up with strategies to prevent this complex disorder.

Sources:
Boyle C, Van Naarden Braun K, Yeargin-Allsopp M. The Prevalence and the Genetic Epidemiology of Developmental Disabilities. In: Genetics of Developmental Disabilities. Merlin Butler and John Meany eds. 2004 (Table 3, p. 716-717).

Muhle R, Trentacoste V, Rapin I. The Genetics of Autism. Pediatrics 2004;113;472-486

Content source: Centers for Disease Control and Prevention

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What role does inheritance play?

Recent studies strongly suggest that some people have a genetic predisposition to autism. In families with one autistic child, the risk of having a second child with the disorder is approximately five percent, or one in 20. This is greater than the risk for the general population. Researchers are looking for clues about which genes contribute to this increased susceptibility. In some cases, parents and other relatives of an autistic child show mild impairments in social and communicative skills or engage in repetitive behaviors. Evidence also suggests that some emotional disorders, such as manic depression, occur more frequently than average in the families of people with autism. Do symptoms of autism change over time?

For many children, autism symptoms improve with treatment and with age. Some children with autism grow up to lead normal or near-normal lives. Children whose language skills regress early in life, usually before the age of 3, appear to be at risk of developing epilepsy or seizure-like brain activity. During adolescence, some children with autism may become depressed or experience behavioral problems. Parents of these children should be ready to adjust treatment for their child as needed.

For more information go to the Beginner’s Guide to Autism and Additional Resources.

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