Alternative names 
Autistic disorder/Autism spectrum; Pervasive developmental delay


Autism is a complex developmental disorder that appears in the first 3 years of life, although it is sometimes diagnosed much later. It affects the brain’s normal development of social and communication skills.

Autism is a spectrum that encompasses a wide range of behavior. The core features include impaired social interactions, impaired verbal and nonverbal communication, and restricted and repetitive patterns of behavior.

The symptoms may vary from quite mild to quite severe. A related, milder condition is Asperger’s syndrome.

Causes, incidence, and risk factors

Autism is a physical condition linked to abnormal biology and neurochemistry in the brain. The exact causes of these abnormalities remain unknown, but this is a very active area of research. It is likely a combination of factors that leads to Autism.

Genetic factors seem to be important. For example, identical twins are much more likely than fraternal twins or siblings to both have Autism. Similarly, language abnormalities are more common in relatives of autistic children. Chromosomal abnormalities and other neurological problems are also more common in families with Autism.

Autism may also be linked to certain changes or abnormalities along the digestive tract. This has raised question about whether diet or other factors may play a role in the disease. For example, there is some question of whether eating certain foods like wheat and milk may worsen symptoms of Autism. The theory is that proteins in these foods (gluten in grains and casein in dairy products) may cause the gut to become leaky in children with Autism. The leakiness introduces certain substances into the brain, possibly contributing to the behavioral problems associated with Autism. Research testing this theory is underway.

The exact number of children with Autism is not known, but estimates suggest that roughly 1 in 1,000 children are affected. Autism affects boys 3 to 4 times more often than girls. Family income, education, and lifestyle do not seem to affect the risk of Autism.

Some parents have heard that the MMR vaccine that children receive may cause Autism. This theory was based, in part, on two facts. First, the incidence of Autism has increased steadily since around the same time the MMR vaccine was introduced. Secondly, children with the regressive form of Autism (a type of Autism that develops after a period of normal development) tend to start to show symptoms around the time the MMR vaccine is given. This is likely a coincidence due to the age of children at the time they receive this vaccine.

Several major studies have found NO connection between the vaccine and Autism, however. The American Academy of Pediatrics and the Center for Disease Control and Prevention report that there is no proven link between Autism and the MMR vaccine.

Some doctors attribute the increased incidence in Autism to newer definitions of Autism. The term “Autism” now includes a wider spectrum of children. For example, a child who is diagnosed with high-functioning Autism today may have been thought to simply be odd or strange 30 years ago.


Most parents of autistic children suspect that something is wrong by the time the child is 18 months old and seek help by the time the child is 2. Children with Autism typically have difficulties in verbal and nonverbal communication, social interactions, and pretend play. In some, aggression - toward others or self - may be present.

Some children with Autism appear normal before age 1 or 2 and then suddenly “regress” and lose language or social skills they had previously gained. This is called the regressive type of Autism.

People with Autism may perform repeated body movements, show unusual attachments to objects or have unusual distress when routines are changed. Individuals may also experience sensitivities in the senses of sight, hearing, touch, smell, or taste. Such children, for example, will refuse to wear “itchy” clothes and become unduly distressed if forced because of the sensitivity of their skin. Some combination of the following areas may be affected in varying degrees.


  • Is unable to start or sustain a conversation  
  • Develops language slowly or not at all  
  • Repeats words  
  • Reverses pronouns  
  • Uses nonsense rhyming  
  • Communicates with gestures instead of words  
  • Has a short attention span

Social interaction

  • Shows a lack of empathy  
  • Has difficulty making friends  
  • Is withdrawn  
  • Prefers to spend time alone rather than with others  
  • Is less responsive to eye contact or smiles

Response to sensory information

  • Has heightened or diminished senses of sight, hearing, touch, smell, or taste  
  • Seems to have a heightened or diminished response to pain  
  • May withdraw from physical contact because it is overstimulating or overwhelming  
  • Does not startle at loud noises  
  • Rubs surfaces or mouths objects


  • Shows little pretend or imaginative play  
  • Doesn’t imitate the actions of others  
  • Prefers solitary or ritualistic play


  • Uses repetitive body movements  
  • Shows a strong need for sameness  
  • “Acts out” with intense tantrums  
  • Has very narrow interests  
  • Demonstrates perseveration (an obsessive interest in a single item, idea, activity, or person)  
  • Displays an apparent lack of common sense  
  • Shows aggression to others or self  
  • Is overactive or is very passive

Signs and tests

Routine developmental screening should be performed for all children at all well-child visits to their pediatrician. Further evaluation is warranted if there is concern on the part of the clinician or the parents. This is particularly true whenever a child fails to meet any of the following language milestones:

  • Babbling by 12 months  
  • Gesturing (pointing, waving bye-bye) by 12 months  
  • Single words by 16 months  
  • Two-word spontaneous phrases by 24 months (not just echoing)  
  • Loss of any language or social skills at any age.

These children might receive an audiologic evaluation, a blood lead test, and a screening test for Autism such as the Checklist for Autism in Toddlers (CHAT) or the Autism Screening Questionnaire.

A clinician experienced in the diagnosis and treatment of Autism is usually necessary for the actual diagnosis.


Because there is no biological test for Autism, the diagnosis will often be based on specific criteria laid out as A, B, and C in the Diagnostic and Statistical Manual IV, as follows.

A. A total of six or more items from (1), (2), and (3), with at least two from (1) and one each from (2) and (3):

  1. Qualitative impairment in social interaction, manifest by at least two of the following:

  • Marked impairment in the use of multiple nonverbal behaviors, such as eye-to-eye gaze, facial expression, body postures and gestures, to regulate social interaction

  • Failure to develop peer relationships appropriate to developmental level

  • Lack of spontaneous seeking to share enjoyment, interests, or achievements with other people (e.g., by lack of showing, bringing, or pointing out objects of interest)

  • Lack of social or emotional reciprocity
      2. Qualitative impairment in communication, as manifest by at least one of the following:

  • Delay in, or total lack of, the development of spoken language (not accompanied by an attempt to compensate through alternative modes of communication such as gesture or mime)

  • In individuals with adequate speech, marked impairment in the ability to initiate or sustain a conversation with others

  • Stereotyped and repetitive use of language, or idiosyncratic languag

  • Lack of varied, spontaneous make-believe, or social imitative play appropriate to developmental level
      3. Restrictive repetitive and stereotypic patterns of behavior, interests, and activities, as manifested by at least one of the following:

  • Encompassing preoccupation with one or more stereotyped and restricted patterns of interest that is abnormal either in intensity or focus

  • Apparently inflexible adherence to specific nonfunctional routines or rituals

  • Stereotyped and repetitive motor mannerisms (e.g., hand or finger flapping or twisting, or complex whole-body movements)

  • Persistent preoccupation with parts of objects.

    B. Delays or abnormal functioning in at least one of the following areas, with onset prior to age 3 years:

      1. Social interaction
      2. Language as used in social communication
      3. Symbolic or imaginative play

    C. The disturbance is not better accounted for by Rett’s disorder or childhood disintegrative disorder.


    The other pervasive developmental disorders include:

    • Asperger’s syndrome  
    • Rett syndrome  
    • Childhood disintegrative disorder  
    • Pervasive developmental disorder - not otherwise specified (PDD-NOS), also called atypical Autism.

    The diagnostic evaluation of Autism will often include a complete physical and neurologic examination, as well as the use of a specific diagnostic instrument such as the Gilliam Autism Rating Scale, the Pervasive Developmental Disorders Screening Test-Stage 3, the Childhood Autism Rating Scale (CARS), or the Autism Diagnostic Observation Schedule-Generic. Children with known or suspected Autism will often have genetic testing (looking for chromosome abnormalities) and perhaps metabolic testing.

    Because Autism encompasses such a broad spectrum, a brief observation in a single setting cannot predict an individual’s true abilities. Ideally, a multidisciplinary team will evaluate the child. This evaluation might include a comprehensive speech-language-communication evaluation, a cognitive and adaptive behavior evaluation, a sensorimotor and occupational therapy evaluation, and neuropsychological, behavioral and academic assessments.

    Sometimes people are reluctant to make the diagnosis of Autism because of concerns about labeling the child. Although pigeonholing in a way that suggests limits is inappropriate due to the wide range of autistic spectrum conditions, failure to make a diagnosis can lead to failure to get the treatment and services the child needs.


    Intensive, appropriate early intervention greatly improves the outlook for most young children with Autism. Most programs will build on the interests of the child in a highly structured schedule of constructive activities. Visual aids are often helpful.

    Treatment is most successful when geared toward the individual’s particular needs. An experienced specialist or team should design the individualized program. A variety of effective therapies are available, including applied behavior analysis, medications, music therapy, occupational therapy, physical therapy, sensory integration, speech/language therapy, and vision therapy. The best treatment plan uses a combination of techniques

    One very successful educational program is called the Treatment and Education of Autistic and Related Communication Handicapped Children (TEACCH).

    In addition, there have been case reports of children with Autism seeing improvement in behavior by following a gluten-free or a casein-free diet. Gluten is found in foods containing wheat, rye, and barley. Casein is found in milk, cheese, and other dairy products. Not all experts agree that dietary changes will make a difference, and not all reports studying this method have shown positive results.

    If considering these or other dietary changes, it is important to seek guidance from both a gastroenterologist (doctor who specialized in the digestive system) and a registered dietitian, who can be sure that the child is still receiving adequate calories, necessary nutrients, and a balanced diet.

    Beware that there are widely publicized treatments for Autism that do not have scientific support, and reports of “miracle cures” that do not live up to expectations. If your child has this condition, it may be helpful to talk with other parents of children with Autism, talk with Autism specialists, and follow the progress of research in this area, which is rapidly developing.

    Support Groups
    For organizations that can provide additional information and help on Autism, see Autism resources.

    Expectations (prognosis)

    Autism remains a challenging condition for individuals and their families, but the outlook today is much better than it was a generation ago. At that time, most people with Autism were placed in institutions. Today, with appropriate therapy, many of the symptoms of Autism can be improved, though most people will have some symptoms throughout their lives. Most people with Autism are able to live with their families or in the community.

    Autism varies from quite mild to quite severe. The outlook for individuals depends on the degree of their disabilities and on the level of therapy they receive.


    Autism can be associated with other disorders that affect the functioning of the brain, such as tuberous sclerosis, mental retardation, or fragile X syndrome. Up to 30% of people with Autism will develop seizures.

    The stresses that Autism places on individuals and their families can also lead to social and psychological complications for all involved. However, some autistic individuals have spectacular talents in particular areas (“autistic savants”) such as art or mathematics.

    Calling your health care provider
    Parents usually suspect Autism long before a diagnosis is made. Call your health care provider with any concerns about Autism or if you are concerned that your child is not developing normally.

    Johns Hopkins patient information

    Last revised: December 4, 2012
    by Amalia K. Gagarina, M.S., R.D.

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