MSD Manual

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Autism Spectrum Disorders


Stephen Brian Sulkes

, MD, Golisano Children’s Hospital at Strong, University of Rochester School of Medicine and Dentistry

Last full review/revision May 2020| Content last modified May 2020
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NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
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Autism spectrum disorders are conditions in which people have difficulty developing normal social relationships, use language abnormally or not at all, and show restricted or repetitive behaviors.

  • Affected people have difficulty communicating with and relating to others.

  • People with an autism spectrum disorder also have restricted patterns of behavior, interests, and/or activities and often follow rigid routines.

  • Diagnosis is based on observation, reports of parents and other caregivers, and standardized autism-specific screening tests.

  • Most people respond best to highly structured behavioral interventions.

Autism spectrum disorders (ASDs) are neurodevelopmental disorders.

Autism spectrum disorders are considered a spectrum (range) of disorders because the manifestations vary widely in type and severity. Previously, ASDs were subclassified into classic autism, Asperger syndrome, Rett syndrome, childhood disintegrative disorder, and pervasive developmental disorder not otherwise specified. However, doctors currently do not use this terminology and consider these all as ASDs (except for Rett syndrome, which is a distinct genetic disorder). ASDs are different from intellectual disability, although many people with ASDs have both. The classification system emphasizes that, within the broad spectrum, different features may occur more or less strongly in a given individual.

These disorders occur in about 1 of 59 people and are 4 times more common among boys than among girls. The estimated number of people identified with an autism spectrum disorder has risen because doctors and caregivers have learned more about the symptoms of the disorder.


The specific causes of autism spectrum disorders are not fully understood, although they are often related to genetic factors. For parents of one child with an ASD, risk of having another child with an ASD is 50 to 100 times greater. Several genetic abnormalities, such as Fragile X syndrome, tuberous sclerosis complex, and Down syndrome, may be associated with ASD. Prenatal infections, for example, viral infections such as rubella or cytomegalovirus, may also play a role. It is clear, however, that ASDs are not caused by poor parenting, adverse childhood conditions, or vaccinations (see also MMR vaccine and autism).

Some children who have an ASD have differences in how their brain is formed and how it functions.

Did You Know...

  • Autism spectrum disorders are not caused by vaccinations.


Symptoms of autism spectrum disorders may appear in the first 2 years of life, but in milder forms symptoms may not be detected until school age.

Children with an autism spectrum disorder develop symptoms in the following areas:

  • Social communications and interactions

  • Restricted, repetitive patterns of behavior

Symptoms of an autism spectrum disorder range from mild to severe, but most people require some level of support in both areas. People with an ASD vary widely in their ability to function independently in school or society and in their need for supports. In addition, about 20 to 40% of children with an ASD, particularly those with an IQ less than 50, develop seizures before reaching adolescence. In about 25% of affected children, a loss of previously acquired skills (regression in development) occurs around the time of diagnosis and may be the initial indicator of a disorder.

Social communications and interactions

Often, infants with an ASD cuddle and make eye contact in atypical ways. Although some affected infants become upset when separated from their parents, they may not turn to parents for security as do other children. Older children often prefer to play by themselves and do not form close personal relationships, particularly outside of the family. When interacting with other children, they may not use eye contact and facial expressions to establish social contact, and they have difficulty interpreting the moods and expressions of others. They may have difficulty knowing how and when to join a conversation and difficulty recognizing inappropriate or hurtful speech. These factors may cause others to view them as odd or eccentric and thus lead to social isolation.


The most severely affected children never learn to speak. Those who learn may do so much later than normal and use words in an unusual way. They often repeat words spoken to them (echolalia), use memorized scripted speech in place of more spontaneous language, or reverse the normal use of pronouns, particularly using you instead of I or me when referring to themselves. Conversation may not be interactive, and, when present, is used more to label or request than to share ideas or feelings. People with an autism spectrum disorder may speak with an unusual rhythm and pitch.

Behavior, interests, and activities

People with an autism spectrum disorder are often very resistant to changes, such as new food, toys, furniture arrangement, and clothing. They may become excessively attached to particular inanimate objects. They often do things repetitively. Younger and/or more severely affected children often repeat certain acts, such as rocking, hand flapping, or spinning objects. Some may injure themselves through repetitive behaviors such as head banging or biting themselves. Less severely affected people may watch the same video multiple times or insist on eating the same food every meal. People with an ASD often have very specialized, often unusual interests. For instance, a child may be preoccupied with vacuum cleaners.

People with an autism spectrum disorder often have over-reactions or under-reactions to sensations. They may be extremely repelled by certain odors, tastes, or textures, or react unusually to painful, hot, or cold sensations that other people find distressing. They may ignore some sounds and be extremely bothered by others.


Many people with an ASD have some degree of intellectual disability (an IQ less than 70). Their performance is uneven. They usually do better on tests of motor and spatial skills than on verbal tests. Some people with an ASD have idiosyncratic or "splinter" skills, such as the ability to carry out complex mental arithmetic or advanced musical skills. Unfortunately, such people often cannot use these skills in a productive or socially interactive way.

Signs of Autism Spectrum Disorders

All signs do not have to be present for a diagnosis of autism spectrum disorder, but children must have difficulties in both A and B. The signs can vary widely in severity, but must impair children's functioning.

A. Difficulties in social communication and interaction:

  • Difficulty engaging with others and sharing thoughts and feelings

  • Difficulty with nonverbal communication (such as making eye contact, understanding and using body language and facial expressions)

  • Difficulty developing, maintaining, and understanding interpersonal relationships

B. Restricted, repetitive patterns of behavior, interests, and/or activities:

  • Repeated movements or speech

  • Inflexible adherence to routines and resistance to change

  • Very restricted, intense interests

  • Very increased or decreased response to physical sensations, such as tastes, smells, textures


  • A doctor's evaluation

  • Reports of parents and other caregivers

  • Standardized autism-specific screening tests

The diagnosis of an autism spectrum disorder is made by close observation of the child in a playroom setting and careful questioning of parents and teachers. Standardized autism-specific screening tests, such as the Social Communication Questionnaire and the Modified Checklist for Autism in Toddlers (M-CHAT-R), may help identify children who need more in-depth testing. Psychologists and other specialists may use the more extensive Autism Diagnostic Observation Schedules and other tools.

In addition to giving standardized tests, doctors do certain blood or genetic tests to look for underlying treatable or inherited medical disorders, such as hereditary metabolic disorders and Fragile X syndrome.


The symptoms of autism spectrum disorders generally persist throughout life. The prognosis is strongly influenced by how much usable language the child has acquired by elementary school age. Children with an ASD who have lower measured intelligence—for example, those who score below 50 on standard IQ tests—are likely to need more intensive support as adults.


  • Applied behavior analysis

  • Educational programs

  • Speech and language therapy

  • Sometimes drug therapy

Applied behavior analysis (ABA) is a therapy doctors use to improve, change, or develop specific behaviors in children who have an ASD. These behaviors include social skills, language and communication skills, reading, and academics as well as learned skills such as self-care (for example, showering and grooming), daily-living skills, punctuality, and job competence. This therapy is also used to help children minimize behaviors (for example, aggression) that may interfere with their progress. Applied behavior analysis therapy is tailored to meet the needs of each child and is typically designed and supervised by professionals certified in behavior analysis.

Educational programs for school-aged children with an ASD should address social skills development and speech and language delays and help prepare children for education after high school or for employment.

The federal Individuals with Disabilities Education Act (IDEA) requires public schools to provide free and appropriate education to children and adolescents with an ASD. Education must be provided in the least restrictive, most inclusive setting possible—that is, a setting where the children have every opportunity to interact with nondisabled peers and have equal access to community resources. The Americans with Disability Act and Section 504 of the Rehabilitation Act also provide for accommodations in schools and other public settings.

Drug therapy cannot change the underlying disorder. However, the selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine, paroxetine, and fluvoxamine, are often effective in reducing ritualistic behaviors of people with an ASD. Antipsychotic drugs, such as risperidone, may be used to reduce self-injurious behavior, although the risk of side effects (such as weight gain and movement disorders) must be considered. Mood stabilizers and psychostimulants may be helpful for people who are inattentive or impulsive or who have hyperactivity.

Although some parents try special diets, gastrointestinal therapies, or immunologic therapies, currently there is no good evidence that any of these therapies are helpful in children with an autism spectrum disorder. Other complementary therapies, such as facilitated communication, chelation therapy, auditory integration training, and hyperbaric oxygen therapy, have not been proved effective. In considering such treatments, families should consult with the child's primary care physician regarding benefits and risks.

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