Version May 2024
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AUTISM SPECTRUM DISORDER OVERVIEW — Autism spectrum disorder (ASD) is a developmental disability that affects how a person interacts with the world. It can cause difficulties with socializing, communicating, and behavior. The term "spectrum" refers to the wide range of symptoms and behaviors a person might have.
In 2013, the criteria used to diagnose ASD and the names of some types of ASD changed. Children who used to be diagnosed with a particular type of autism (such as Asperger syndrome) are now given the diagnosis of ASD. ASD is then classified according to whether it co-exists with a language impairment or intellectual disability and by the level of severity and degree of support needed for its two core symptoms (problems with social communication and restricted and repetitive behaviors). There are three levels (1, 2, and 3) which indicate how much support the person requires in each of these areas.
Some people also use the word "neurodiversity" to describe the different ways people's brains can work; this can include ASD as well as other conditions, like attention deficit disorder or learning disabilities.
How does autism spectrum disorder develop? — It is not clear how or why ASD develops. The general consensus is that ASD is a neurodevelopmental disorder that affects brain development and impairs the development of social and communication skills. This, in turn, leads to the typical symptoms of ASD. (See 'Symptoms of autism spectrum disorder' below.)
In most children, the cause of ASD is unknown. Environmental factors such as toxic exposures before or after birth, complications during delivery, and maternal infections during pregnancy may be responsible for a small percentage of cases. In children with a genetic predisposition, environmental factors may further increase the child's risk of developing ASD.
Some people believe, incorrectly, that ASD is caused by exposure to certain vaccines or vaccine components (particularly measles vaccines and thimerosal, a mercury preservative used in vaccines). However, the main study that claimed to find a link between vaccines and ASD was found to be false and retracted. There is no evidence that any vaccines cause ASD. (See "Patient education: Why does my child need vaccines? (Beyond the Basics)", section on 'Vaccine safety'.)
How common is autism spectrum disorder? — The number of children diagnosed with ASD in the United States and other countries has increased since the 1970s and particularly since the late 1990s. It is not clear if the increase is related to the changes in the criteria used to diagnose ASD (meaning more children with ASD symptoms are being identified than previously) or if the condition has truly become more common over time. Most experts agree that increased awareness and changes in the definition of ASD account for much of the apparent increase in the prevalence of ASD.
Between 2 and 25 out of 1000 children have ASD, and it affects more males than females (approximately four males for every one female) [1,2]. Approximately 4 to 14 percent of siblings of children with ASD also have the condition, but the risk may be higher [3-6].
Medical conditions associated with autism spectrum disorder — There are a number of medical conditions associated with ASD:
●Approximately 33 percent of children with ASD have an intellectual disability, such as language delay or learning difficulties [7].
●Approximately 30 percent of children with ASD have seizures. The risk of seizures is higher in people with more severe intellectual disability. (See "Patient education: Seizures in children (Beyond the Basics)".)
●Up to 25 percent of cases of ASD are associated with a specific medical condition or syndrome. Examples include tuberous sclerosus, fragile X syndrome, Rett syndrome, phenylketonuria, fetal alcohol syndrome, or Angelman syndrome.
SYMPTOMS OF AUTISM SPECTRUM DISORDER — Symptoms of autism spectrum disorder (ASD) are usually recognized between two and three years of age, although they may be present earlier. By definition, symptoms must be present in early development, but sometimes the symptoms are not apparent until the child is older. Symptoms cluster into two broad areas: 1) social communication and 2) restricted and repetitive behavior, activities, and interests.
Speech or language delay noticed by the caregivers or primary care provider often is the first sign that a child may have ASD. Less common signs include lack of eye contact or little interest in other people. Reasons for caregivers to seek help are discussed below. (See 'When to seek help' below.)
Social interaction and communication — Difficulties with social interaction and communication are the most common reason caregivers seek medical evaluation for children with ASD. The child may not be able to speak or understand others, and/or may show no interest in communicating.
Social interaction — Difficulty with or lack of interaction with family and friends is a hallmark of ASD. Social interaction includes nonverbal behaviors, peer relationships, joint attention, and social reciprocity (which are explained below).
Individuals with ASD often have a hard time learning to interact with other people. Younger children may have little or no interest in developing friendships. They may prefer to play alone rather than playing with others, and may involve others in activities only as tools or "mechanical" aids (ie, using the hand of a caregiver to obtain a desired object without making eye contact).
Older children may become more interested in talking or socializing with other people but may not understand social conventions or the needs of others. As an example, the child may continue talking about a topic of their own interest with complete disregard for the interests of the listener.
People with ASD are often not interested in or are not able to share activities, interests, or achievements; this is referred to as "impaired joint attention." Joint attention is a normal behavior in which an infant or toddler tries to share interest, amusement, or fear with a caretaker. The child does this by purposefully looking back and forth between an object and the eyes of the caretaker (usually by 8 to 10 months of age) or by pointing to the object (usually by 14 to 16 months of age). Older children with ASD may not show or bring an object to the caretaker.
People with ASD are sometimes not able to share a pleasurable activity with others. As an example, a child may prefer to play alone amidst a crowd of children engaged in the same activity.
Nonverbal behaviors — People with ASD have difficulty using and interpreting nonverbal behaviors such as eye contact, facial expression, gestures, and body postures. For example, a child may not be able to understand the facial expressions associated with anger or annoyance, or may not be able to use eye contact or a gesture to indicate a want.
During infancy, caregivers may notice that the baby resists cuddling, avoids eye contact, or does not spread the arms in anticipation of being picked up; however, these behaviors are not universal.
Restricted and repetitive behavior, activities, and interests
Stereotyped behaviors — Another behavioral feature of ASD is repetitive body movements, such as hand or finger flapping or twisting, rocking, swaying, dipping, or walking on tip-toe. These behaviors are sometimes called "stimming"; they are seen in 37 to 95 percent of people with ASD and commonly begin during the preschool years. These behaviors are often lifelong.
Insistence on sameness — Many children with ASD have specific routines or rituals that must be followed exactly. These may occur as a part of daily life, such as the need to always eat particular foods in a specific order or to follow the same route from one place to another without deviation. Changes in routine can be upsetting or frustrating, sometimes leading to a tantrum or meltdown. Although these behaviors also occur in typically developing children, in typically developing children they have a lower intensity and tend to decrease by kindergarten age.
Restricted interests — Younger children with ASD may be preoccupied with peculiar sensory objects or experiences, such as spinning objects, shiny surfaces, the edge of objects, lights, odors, or sniffing or licking nonfood objects.
Older children may be preoccupied with the weather, dates, schedules, phone numbers, license plates, cartoon characters, or other items (eg, dinosaurs, dogs, planes).
Sensory perception — Many people with ASD show atypical sensory responses to sounds, tastes, or touch. For example, the person may be overly sensitive to normal noise levels or have no response to loud noises.
Other examples include:
●Refusal to eat foods with certain tastes or textures, or eating only foods with certain tastes and textures. These dietary obsessions can cause gastrointestinal symptoms, such as weight loss, diarrhea, or constipation.
●Resistance to being touched or increased sensitivity to certain kinds of touch; light touch may be experienced as painful, whereas deep pressure may provide a sense of calm. This may include resistance to the feel of certain clothing textures or colors next to the skin.
●Apparent indifference to pain.
Hypersensitivity to certain frequencies or types of sound (eg, distant fire engines) and lack of response to sounds close by or sounds that would startle other children (eg, firecrackers).
Other features
Cognitive skills — Cognitive skills include the ability to think, remember, and process information. In children with ASD, these skills are often uneven, regardless of the child's level of intelligence. The person can often perform tasks that require memorization or putting things together (eg, puzzles), but may have difficulty with tasks that require other skills, such as reasoning, interpretation, or abstract thinking.
Some individuals have special skills or strengths (sometimes called "savant" skills) in memory, mathematics, music, art, or puzzles, despite significant difficulties in other areas. Other special skills can include calendar calculation (determining the day of the week for a given date) and hyperlexia (the ability to read written words that are far above the person's reading level). However, the person may not understand what is being read or the purpose of reading.
Language skills — A delayed or absent ability to speak may be the first sign of ASD. Unlike children with a hearing impairment, children with ASD do not try to compensate for their lack of speech by using alternate means of communication, like gesturing or miming. In most individuals with ASD, the ability to understand is delayed even more than the ability to speak. Children may not respond to their name, and the caregiver may initially be concerned that the child has a hearing problem. A child may not be able to understand simple questions or directions.
There is wide variability in the severity and quality of language problems in children with ASD. Some children never develop the ability to speak. In others, the child is able to speak, but language is not used as a tool for communication (eg, it consists of repeating phrases or words spoken by others, called echolalia).
Those who are able to speak may have difficulty starting or sustaining a conversation with others. Their language may have meaning only to people who are familiar with the communication style of the person with ASD.
AUTISM SPECTRUM DISORDER DIAGNOSIS — Children with symptoms of autism spectrum disorder (ASD), may be evaluated by a team that has expertise in diagnosing and managing the condition. This team often includes a child psychologist, developmental-behavioral pediatrician, neurologist, psychiatrist, speech therapist, and other professionals. The diagnosis of ASD also may be made by a single clinician with expertise in diagnosing ASD. In locations that do not have access to such a team of subspecialists, primary care clinicians may team up with early intervention or public school professionals to make an ASD diagnosis.
The evaluation usually includes a complete medical history (of the child and family), physical examination, neurologic examination, and testing of the child's social, language, and cognitive skills. In addition, the caregiver(s) will have time to discuss the child's behavior and any other concerns.
The purpose of the evaluation includes the following:
●Determine if the child has ASD or if another condition could be causing the child's symptoms
●Determine if the child has ASD and a co-existing condition
●Determine if the child has any ASD-associated medical problems that should be evaluated or treated
●Determine the child's strengths, weaknesses, and level of functioning
WHEN TO SEEK HELP — Some common symptoms of autism spectrum disorder (ASD) are listed in the table (table 1).
Caregivers who notice that their child has one or more symptoms of ASD should talk to the child's health care clinician. The clinician should screen the child for ASD and potentially team up with local early intervention or public school special education professionals to make a diagnosis.
If the provider's evaluation suggests the possibility of ASD, the child could also be referred for a complete evaluation for ASD. Early diagnosis and treatment of ASD can modify some behaviors consistent with ASD and improve socialization. (See 'Autism spectrum disorder diagnosis' above.)
Even before the complete evaluation, the child should be referred for a hearing and vision test (if not done previously) and for early intervention services. Early intervention is a support and treatment system that provides appropriate therapies for children with disabilities. It can help to minimize delays and maximize the child's chance of reaching normal milestones in development. If the child is already three years of age, they should be referred for special education services. Even if the child is not diagnosed with ASD, early intervention services or special education services can help to address caregivers' concerns (eg, delayed language skills, temper tantrums).
AUTISM SPECTRUM DISORDER TREATMENT — Autism spectrum disorder (ASD) cannot be cured. However, a health care clinician can work with caregivers to develop a treatment plan to help the child reach their full potential. The optimal treatment plan depends upon the child's age, diagnosis, underlying medical problems, and other individual factors.
The American Academy of Pediatrics recommends a plan that provides structure, direction, and organization for the child [3]. In the United States, services are often provided through an early intervention program up to three years of age; after age three they are provided in the form of an Individualized Education Program (IEP) through the local public school system. Information about services for children with ASD is available through the Center for Parent Information and Resources and the Center for Autism Research (CAR) Autism Roadmap.
Other resources for caregivers and providers are listed below. (See 'Where to get more information' below.)
How can I support my child? — If your child has ASD, it can help to learn more about the condition to better understand how their brain works. While certain types of support and therapy can help your child feel more comfortable interacting with the world, you can also help them by making it clear that you accept who they are.
As your child gets older, they might also be able to learn to advocate for themselves. This might include explaining to other people that their brain works differently or requesting certain types of support. If your child cannot advocate for themselves, you can be an advocate for them.
WHERE TO GET MORE INFORMATION — Your child's health care provider is the best source of information for questions and concerns related to your child's medical problem.
This article will be updated as needed on our website (www.uptodate.com/patients). Related topics for patients and caregivers, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.
Patient-level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient education: Autism spectrum disorder (The Basics)
Patient education: Learning disabilities (The Basics)
Patient education: Fragile X syndrome (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient education: Why does my child need vaccines? (Beyond the Basics)
Patient education: Seizures in children (Beyond the Basics)
Professional-level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Autism spectrum disorder and chronic disease: No evidence for vaccines or thimerosal as a contributing factor
Autism spectrum disorder in children and adolescents: Clinical features
Autism spectrum disorder in children and adolescents: Evaluation and diagnosis
Autism spectrum disorder in children and adolescents: Screening tools
Autism spectrum disorder in children and adolescents: Surveillance and screening in primary care
Autism spectrum disorder (ASD) in children and adolescents: Terminology, epidemiology, and pathogenesis
The following organizations also provide reliable health information.
●National Institute of Mental Health
(www.nimh.nih.gov/health/topics/autism-spectrum-disorders-asd)
●Medline Plus
(www.nlm.nih.gov/medlineplus/autism.html, available in Spanish)
●National Institute of Neurological Disorders and Stroke
●United States Center for Disease Control and Prevention
(www.cdc.gov/ncbddd/autism/index.htm)
●Autism Speaks
●Autism Society of America
●The Autism Navigator, an online collection of resources including videos of children with early signs of ASD (available for free with registration)
●Learn the Signs. Act Early.
(www.cdc.gov/ncbddd/actearly/index.html)
●The United Kingdom's National Autistic Society
●Federation for Children with Special Needs
(fcsn.org)
●Asperger/Autism Network
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