Autism Spectrum Disorder

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What is autism spectrum disorder?

Autism spectrum disorder (ASD) is a group of chronic neurologic and developmental disorders. People with ASD have social, communication, language and behavioral problems. They may also display extremely repetitive routines and behaviors. These problems range from mild to severe, covering a broad spectrum of disabilities.

Symptoms of ASD typically appear in early childhood and continue for a person’s lifetime. The symptoms and their severity vary greatly from child to child and among the different forms of ASD.

The Centers for Disease Control and Prevention (CDC) estimates 1 in 54 American children at age 8 has ASD. (The CDC measures ASD in children who are 8 years old because research shows that most children with ASD have been identified and diagnosed by this age.) This prevalence is up from 1 in 150 children (aged 8 years) in 2000.

ASD occurs in both genders, but boys are four times more likely to have it than girls. ASD also appears in all ethnicities, socioeconomic levels, and geographic areas. It occurs at a higher rate among children born to older parents and to parents with an age difference of more than 10 years.

Health experts do not fully understand what causes ASD. While research continues on the possible causes, the scientific community recognizes that ASD is not due to bad parenting.

There is no cure for ASD at this time. However, a variety of therapies and other treatments are available to help people with ASD and their families manage the social, communication, language and behavioral challenges. Researchers around the world are studying ASD to learn more about the causes and develop effective treatments.

Seek prompt medical care if your child has symptoms of ASD, such as delays in normal development or lack of language or social skills. Early detection and diagnosis of ASD improves the likelihood of successful treatment.

Sometimes, people with ASD can exhibit aggressive behavior. Seek immediate medical care (call 911) if someone with ASD becomes violent, threatening, or dangerously aggressive, or is hurting himself or herself.

Is autism the same as autism spectrum disorder?

In 2013, the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) reclassified what were previously four separate conditions—Asperger syndrome, autistic disorder, pervasive developmental disorder not otherwise specified (PDD-NOS), and childhood disintegrative disorder (CDD)—under one umbrella term: autism spectrum disorder.

This new term helps ensure a more accurate and reliable diagnosis, and is broken into levels of severity rather than different condition types. Today, the word “autism” may be used to refer to any level of symptoms classified under autism spectrum disorder, and the two terms—autism and ASD—are often used interchangeably.

While the DSM-5 says all previous diagnoses should now be classified as ASD, many people who were diagnosed prior to the change feel attached to their specific conditions, particularly those who identify as having Asperger’s. Some of these patients may still use the older terms to describe themselves, and their medical records may reflect the previous diagnosis as well as ASD.

Prior to the DSM-5, autism spectrum disorder was diagnosed as one of the following conditions:

Asperger syndrome

Asperger syndrome (Asperger’s) applies mainly to children with social issues. Most people with Asperger’s (who sometimes called themselves “Aspie”) have no problems with speech during early childhood. Some kids with Asperger’s have very specific and intense interests. They may be fascinated with a particular subject.

Some people with Asperger’s are gifted or have remarkable talents in a certain area. They may be less involved in a wide range of interests compared to other people of the same age. This can make them seem socially awkward.

Other signs of Asperger’s include:

  • Avoiding eye contact
  • Not understanding nonverbal cues like a smile or a frown
  • Not seeing things from another’s perspective
  • Talking only about oneself

The disorder affects up to four times more boys than girls. It's not clear how common it is. Estimates range from 1 of every 250 children to 1 of 5,000.

People with Asperger’s are high-functioning and are considered level 1 under the current DSM-5 criteria for ASD. Many children don't get a diagnosis until they are in middle school. Those with mild forms of the disorder may never be diagnosed.

Autistic disorder 

Autistic disorder (Kanner's syndrome) affects about 1 in 1,000 children. Kids with this type of autism have at least six symptoms affecting these key areas:

  • Ability to communicate
  • Interaction with others
  • Interests or behavior

Often, children with autistic disorder do not want to be social. They may have a lot of trouble communicating. They may learn to speak later than usual. Children with these symptoms are considered level 2 or level 3 ASD under the current DSM-5 diagnostic criteria.

Pervasive developmental disorder not otherwise specified (PDD-NOS) 

PDD-NOS affects about 3 of every 1,000 children. Children with PDD-NOS may have trouble with social skills but not with language or behavior.

They usually fall into one of these groups:

  • Those who have mild symptoms of autism
  • Those who do not meet all of the criteria for an autistic disorder
  • Those with some Asperger’s symptoms as well as a language delay

Under the new DSM-5, these children would likely receive the new diagnosis of social communication disorder. This is considered a communication disorder and is not on the autism spectrum.

Childhood disintegrative disorder (CDD) 

CDD is very rare. CDD affects an estimated 2 of every 100,000 children.

Autism is usually diagnosed before the age of 3, but children with CDD don't usually get a diagnosis until they're 4 to 10 years old.

These children develop normally for at least the first two years of life. Then, they lose the skills they have gained. This includes the ability to speak. CDD can also affect the use of certain muscles and social skills. Some children with CDD also have seizures.

What are the levels of autism spectrum disorder?

With the change in terminology established by the DSM-5, autism spectrum disorder (ASD) is now categorized by severity rather than broken into different types.

Based on the extent of social communication issues and presence of restrictive, repetitive behaviors, doctors evaluate ASD by these severity levels:

  • Level 1 (“Requiring support”): The person is verbal and can speak in complete sentences, but has noticeable impairments when socializing and forming relationships. He or she may have difficulty switching between activities, planning ahead, or staying organized, which can limit independence.
  • Level 2 (“Requiring substantial support”): Even with support, the person has significant difficulty with verbal and nonverbal communication, including an inability to speak in complex sentences. Responses to others may be limited or abnormal, and interactions may be focused on narrow special interests. Behavior is increasingly inflexible with a strong resistance to change and distress when transitioning to a new activity.
  • Level 3 (“Requiring very substantial support”): Social communication skills are severely lacking, and the person is essentially nonverbal, with a limited range of intelligible speech. Repetitive and restrictive behaviors significantly interfere with normal function, and changing focus or action causes extreme distress.

The DSM-5 also introduced a new diagnosis of social communication disorder, a term to describe problems with social interactions and language that are not accompanied by restrictive or repetitive behaviors. Social communication disorder is not part of the autism spectrum. However, people who previously would have been diagnosed with pervasive developmental disorder not otherwise specified (PDD-NOS) might now be diagnosed with social communication disorder.

What are the symptoms of autism spectrum disorder?

Symptoms of autism spectrum disorder (ASD) begin early in life. Parents of children with ASD generally notice symptoms by their child’s first or second birthday.

Common symptoms of ASD include social and language problems, abnormally repetitive routines and behaviors, and extreme sensory feelings. However, specific behaviors and symptoms vary in nature and severity from person to person.

Communication and language symptoms of ASD

Many people with ASD find it difficult to communicate. The following are communication-related symptoms of ASD:

  • Answers questions with unrelated answers
  • Communicates with gestures instead of words or vice versa
  • Does not develop language or develops it very slowly
  • Does not understand or use social cues, such as facial expressions and gestures
  • Interprets what other people say very literally, and does not easily understand jokes or irony
  • Repeats his or her own words or phrases over and over, or repeats what other people say
  • Uses pronouns incorrectly, such as “You would like some water” instead of “I would like some water”

Social symptoms of ASD

People with ASD have social habits that cause them problems in everyday life. This includes:

  • Dislike of physical contact
  • Inability to maintain eye contact
  • Lack of empathy, which is the ability to understand other people’s feelings
  • Solitary play; children with ASD do not make friends easily

Behavioral symptoms of ASD

Behaviors that many people with ASD exhibit include:

  • Abnormal sensitivity or insensitivity to the way things look, feel, sound, taste or smell
  • Aggressive and violent temper tantrums
  • Attachment to routines, and inability to cope if things happen outside the routine
  • Attachment to certain objects
  • Extreme impulsivity and hyperactivity
  • Obsessive interest in certain objects or topics (for example, insects)
  • Repetitive or inappropriate activities (for example, licking all the windows on toy cars)
  • Repetitive body movements, such as rocking, flapping arms, rubbing fingers together, and spinning in circles. These are sometimes referred to as “stimming.”
  • Self-abusive behaviors, such as head banging and biting

Serious symptoms that might indicate a life-threatening situation

In some cases, a child or adult with ASD can become violent and pose a danger to herself or others. Seek immediate medical care (call 911) if someone with ASD has any of these symptoms:

  • Suicidal thoughts or a desire to hurt oneself or others
  • Violent or threatening behavior

What causes autism spectrum disorder?

Health experts do not definitively know what causes autism spectrum disorder (ASD). Scientists and researchers are exploring numerous environmental and genetic influences that may make babies and children more likely to develop ASD. This includes the use of certain medications during pregnancy, other medical conditions present at birth, viral infections during pregnancy or during infancy, and chromosomal abnormalities.

Genetics is thought to play a larger role than environmental factors in autism, based on studies of identical and fraternal twins and many other reports. Poor parenting practices do not cause ASD.

There has also been a lot of discussion and research about whether childhood vaccines are linked to ASD. Research from the Centers for Disease Control and Prevention (CDC) and the Institute of Medicine (IOM) shows that vaccines do not cause ASD. These organizations also emphasize that the benefits of vaccines outweigh any risks from them.

What are the risk factors for autism spectrum disorder?

Researchers have identified certain risk factors that increase the likelihood of developing autism spectrum disorder (ASD). Not all people with risk factors will get ASD.

Risk factors for autism spectrum disorder include:

  • Fetal distress before, during or immediately after birth
  • Gene variations, including mutations or chromosomal defects; more than 100 genes are associated with ASD.
  • Genetic conditions, such as Down syndrome, fragile X syndrome, Rett syndrome, and tuberous sclerosis
  • Having a sibling with ASD. The risk is 10 times that of someone without an affected sibling; there is an even greater risk for identical twins.
  • Being born to an older father (50 years vs. 20-29 years), an older mother (40-49 years vs. 20-29 years), or younger mother (younger than 20 vs. 20-29 years); risk increases more when both parents are older.
  • Male gender
  • Maternal use of prescription drugs valproic acid, thalidomide (sedative), or serotonin-reuptake inhibitors (SSRIs) during pregnancy

The current theory is that, in most cases, ASD develops in children with a specific combination of genetic and environmental risk factors that make them susceptible. Multiple factors are at play in any given individual, and the specific set of factors differs between affected individuals.

More information into the causes of ASD may come from brain imaging and other research. Past studies have shown a link between the development of ASD and increases in cerebrospinal fluid starting at 6 months of age and in brain volume between 12 to 24 months.

How do you prevent autism spectrum disorder?

It is not possible to prevent autism spectrum disorder. However, early diagnosis and intervention can help make treatment more successful and improve management of ASD. Talk to your child’s pediatrician about routine screening for autism spectrum disorder and symptoms you need to watch for that could be early signs of ASD.

Preventing injury and abuse of someone with ASD

The symptoms of ASD can also make affected people more vulnerable to other risks. For example, about 50% of children with ASD are prone to wandering, which can put them in dangerous or even fatal situations, such as getting lost away from home or falling into a body of water without knowing how to swim.

Parents can take steps to prevent and reduce risk of wandering and other ASD-related injury, including:

  • Ensure your home is safe and securely locked, from both the inside and outside.
  • Have your child wear a locating device or GPS tracking monitor.
  • Place some type of medical ID, including your contact information, on your child, particularly if he or she is nonverbal. This can be a bracelet or even a temporary tattoo if your child is sensitive to wearing jewelry.
  • Alert your neighbors about possible wandering and give them an action plan to follow if they think your child needs help.
  • Talk to local first responders proactively to inform them of possible wandering and coordinate an effective response plan.
  • Teach your child how to swim.

Children and adults with developmental disabilities are also more likely to be targets of physical, emotional or sexual abuse. Stay alert to any sudden changes in weight, unexplained bruises, and changes in mood or behavior. In nonverbal people, you may notice developmental regression, avoidance of specific people or places, or increased tantrums or outbursts. Talk to your doctor about how to monitor for signs of abuse, how to educate and protect someone with ASD, and what to do if you suspect any type of abuse has occurred.

What are diet and nutrition tips for autism spectrum disorder?

Mealtime with autism spectrum disorder (ASD) can be stressful for both affected children and their families. A child with ASD may have heightened sensitivities or aversions to certain foods—and an inability to communicate exactly what those are—which can limit their options for meals. Behavioral issues can also make breakfast, lunch or dinner a struggle, as parents try to get their children with ASD to eat healthy meals and get proper nutrition.

Some parents report success through alternative diets, such as those free of gluten or dairy, which they say help reduce the frequency and severity of autism symptoms. However, doctors warn that these types of restrictive diets make it more difficult for children to get adequate nutrition, particularly important minerals like calcium.

Families who turn to child-pleasing foods that are high in sugar and fat also risk poor nutrition in children with ASD, increasing their likelihood of obesity, heart disease, and other chronic conditions.

Lack of proper nutrition in turn leads to poor physical, emotional, and cognitive development, underscoring the importance of finding healthy options for the picky eating habits of a child with ASD. Some tips you can try to encourage your child to try new foods and participate in family meals include:

  • Avoid arguing about your child’s eating, both with the child and with other adults at the table. Making food a source of conflict will only exacerbate your child’s anxiety around it.
  • Confirm there is not a physical or medical reason your child is not eating a certain food. Does he or she have a stomach ache? Does the food seem “off”? Your child may have a perfectly rational reason for not eating.
  • Have your child help with food preparation, so he or she feels more invested in what is being served. This can also be an opportunity for your child to learn about the varieties of food available and the value of good nutrition.
  • Offer your child a limited selection of choices to give a sense of being in control, rather than force one specific food on him or her. Just like adults, kids with ASD have food preferences, and the more they can exercise them, the more likely they will be to participate in the meal.
  • When trying a new food, take time to “explore” the food together. What does it look like? How does it smell? What texture does it have? Make trying the new food a team experiment and gradually work your way up to tasting it.

If you are concerned about your child’s eating habits with ASD, talk to your doctor about meeting with a registered dietitian. Together, you can develop a plan to address mealtime challenges and ensure your child is getting the nutrition he or she needs to thrive.

What are some conditions related to autism spectrum disorder?

Conditions related to autism spectrum disorder include:

  • Attention-deficit/hyperactivity disorder (ADHD)
  • Fragile X syndrome, a genetic condition marked by intellectual disability, behavioral symptoms, and some physical characteristics
  • Intellectual disability, developmental delay, or behavioral problem
  • Landau-Kleffner syndrome, a rare neurological disorder that develops between the ages of 5 and 7; characterized by loss of language skills
  • Language delay
  • Prader-Willi syndrome, a rare genetic disorder affecting appetite, cognitive function, and behavior
  • Rett syndrome, a rare neurological disorder caused by MECP2 gene mutations; symptoms include learning and speech challenges, abnormal digestion, and altered movements, among other symptoms.
  • Sensory integration disorder
  • Tuberous sclerosis, a rare genetic disease in which tumors grow in the brain and other organs; symptoms include developmental delays, behavioral problems, seizures, and skin and kidney diseases.

How do doctors diagnose autism spectrum disorder?

An autism diagnosis is based on evaluating the child’s behavior, developmental history, and the parents’ observations. Although diagnosis of ASD can occur at any age, the average age of an ASD diagnosis is 4 years old. The average age for diagnosing Asperger syndrome, a subtype of ASD, is about 5.5 years.

The American Academy of Pediatrics recommends providers screen for autism at 18- and 24-month-old well-child visits, but the child may show signs at earlier well-child visits, even when the baby is less than 12 months old. Earlier diagnosis often means earlier, more effective management of ASD’s challenges.

Autism diagnosis guidelines involve two levels of autism screening.

Stage 1 autism screening checks for the following signs of a developmental delay:

  • No babbling, pointing or gesturing by age 12 months
  • No single words spoken by age 16 months
  • No two-word, spontaneous expressions (non-echolalic, or not merely repeating the sounds of others) by age 24 months
  • Loss of any language or social skills at any age
  • No eye contact at 3 to 4 months

Stage 2 autism screening occurs if the first level of screening diagnoses a child with a developmental delay. The second level is a more in-depth diagnosis and evaluation that can differentiate autism from other developmental conditions. Second level tests may include:

  • Brain scan
  • Genetic testing
  • Metabolic testing
  • Neurological evaluation
  • Psychological evaluation

Parents and educators are typically the drivers of evaluating older children and adolescents for ASD. Diagnosing an adult with autism will likely involve stage 2 screening tests as well as the patient’s self-reported behavioral concerns. Developmental milestone information may be helpful if available from the patient’s parents or guardians.

What are the treatments for autism spectrum disorder?

There is no cure for autism spectrum disorder (ASD), and many autistic people do not need treatment, perhaps because their autistic traits are more neutral or viewed positively. However, autistic children and adults with more severe symptoms, such as self-injurious behavior or a co-occurring condition, may benefit from treatment. There are specialized behavioral and educational programs to treat aspects of autism that interfere with daily life and function or learning.

Each person with ASD has unique behaviors and symptoms, and requires a personalized treatment plan. A child’s family, doctors, therapists and educators can work together to make the best plan. In general, treatment is more successful the earlier it begins after diagnosis.

Behavioral, educational and physical therapies

  • Applied behavior analysis (ABA), a behavioral therapy approach that teaches and strengthens positive behaviors. 

ABA has come under controversy in recent years, with critics saying the emphasis on reducing or eliminating undesirable behaviors, such as a repetitive gesture (known as “stimming”), harms children who are neurodivergent by forcing them to fit the mold of a “typical” child. However, ABA advocates say the process has evolved to be more about fostering independence than changing behavior, with a play-based approach that respects and appreciates the individuality of neurodivergent patients.

Talk with your child’s doctor or ASD specialist to determine your family’s treatment goals and whether ABA is the right option for you and your child.

  • Special education, which focuses on developing social, speech-language, self-care, and job skills, usually in an education setting. Support groups may be part of a special education program.
  • Social skills training, a type of behavioral therapy that focuses on learning how to interpret social cues, start a conversation, and more.
  • Parent education and counseling to teach parents (and families) about autism and how to more effectively interact with their child in a constructive and positive way, as well as build upon behavioral therapy techniques.
  • Psychological therapy to help someone with ASD identify their strengths and challenges, and learn effective coping strategies.

Occupational therapy, sensory integration therapy, and speech therapy may also be helpful.


Medications cannot cure ASD, but they can reduce the severity of certain symptoms, such as anxiety, hyperactivity, aggression, and mood swings. Medications include:

  • Anti-anxiety and antidepressant medications to help minimize anxiety and stabilize mood
  • Antipsychotic medications for individuals with severe behavioral symptoms
  • Stimulants, such as the type used for people with attention deficit disorder

Other therapies

Other therapies that can help include dietary changes, massage therapy, and alternative medicines.

How does autism spectrum disorder affect quality of life?

Many studies show quality of life is much lower for people on the spectrum. The factors that affect quality of life differ between children and adults with ASD.

In children with ASD, older age, social challenges, special education services, and co-occurring psychiatric conditions are found to lower quality of life. In contrast, children who engage in leisure activities report a higher quality of life. Learning adaptive behaviors necessary for daily living is also associated with higher quality of life.

In adults with ASD, behavior problems had a negative effect on quality of life, as did a history of bullying, co-occurring psychiatric conditions, and perceived stress. Participation in leisure and social activities had a positive effect. Autism severity, IQ, and supporting work and residential programs did not affect quality of life.

What are the potential complications of autism spectrum disorder?

With time, many symptoms of ASD can improve. However, if a person does not receive adequate treatment or support, complications can include:

  • Chronic stress
  • Disability including the inability to function effectively at school or work
  • Increasingly disruptive behaviors and habits
  • Injury or even death due to accidents, such as during periods of wandering
  • Isolation due to difficulty socializing and forming relationships 
  • Lasting effects of self-injury
  • Suicidal thoughts or actions. If you suspect someone may be considering suicide, contact his or her doctor or call the National Suicide Prevention Lifeline at 1-800-273-8255. If someone is engaging in self-harm or threatening suicide, call 911.

Does autism spectrum disorder shorten life expectancy?

Autism spectrum disorder (ASD) itself does not shorten someone’s life expectancy, but its effects double a person’s mortality risk. This is primarily due to increased danger or vulnerability caused by symptoms of ASD, such as wandering, self-harm, and exposure to abuse by others. An estimated 28% of people with ASD die of an injury, and someone with ASD is 40 times more likely to die from an injury than someone without the condition.

ASD also increases risk of death by seizures; anywhere from 20 to 40% of people with ASD experience seizures, versus 1% of the overall population.

Finally, the social and cognitive challenges of ASD can be overwhelming. As a result, the suicide rate among people with ASD is nine times higher than that of the general population, and suicide ranks as a top cause of death for people with autism spectrum disorder. (If you suspect someone may be considering suicide, contact his or her doctor or call the National Suicide Prevention Lifeline at 1-800-273-8255. If someone is engaging in self-harm or threatening suicide, call 911.)

As experts learn more about the reasons behind these increased risks, they can work toward improved treatments, help create safer care environments, and improve the prognosis for people with autism spectrum disorder.

Autism spectrum disorder awareness

The U.S. government is using data from the Autism and Developmental Disabilities Monitoring (ADDM) Network to estimate the number of children with autism spectrum disorder (ASD), increase the rate of early ASD evaluation and intervention, and guide research of the condition.

April is World Autism Month.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 May 4
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Autism Fact Sheet. National Institute of Neurological Disorders and Stroke.
  2. Autism Spectrum Disorder. National Institute of Mental Health.
  3. Autism Spectrum Disorder (ASD). Centers for Disease Control and Prevention.
  4. PDD-NOS. Autism Speaks.
  5. Vaccines Do Not Cause Autism. Centers for Disease Control and Prevention.
  6. Autism Resource Center. American Academy of Child and Adolescent Psychiatry.
  7. Sandin S, Schendel D, Magnusson P, et al. Autism risk associated with parental age and with increasing difference in age between the parents. Mol. Psychiatry. 2016;21(5):693-700.
  8. Croen LA, Grether JK, Yoshida CK, et al. Antidepressant Use During Pregnancy and Childhood Autism Spectrum Disorders. Arch Gen Psychiatry. 2011;68(11):1104-1112.
  9. Amaral DG. Examining the Causes of Autism. Cerebrum. 2017 Jan-Feb;2018:cer-01-17.
  10. Levy SE, Mandell DS, Schultz RT. Autism. Lancet. 2009;374(9701):1627–1638.
  11. Geschwind DH, State MW. Gene hunting in autism spectrum disorder: on the path to precision medicine. Lancet Neurol. 2015;14(11):1109–1120.
  12. Shen MD, Piven J. Brain and behavior development in autism from birth through infancy. Dialogues Clin Neurosci. 2017;19(4):325–333.
  13. Differential Diagnosis. Autism Society.
  14. Tuberous Sclerosis Fact Sheet. National Institute of Neurological Disorders and Stroke.
  15. What is Rett syndrome?
  16. Making an Autism Spectrum Disorder Diagnosis. Centers for Disease Control and Prevention.
  17. Hong J, Bishop-Fitzpatrick L, Smith L, et al. Factors Associated with Subjective Quality of Life of Adults with Autism Spectrum Disorder: Self-Report vs. Maternal Reports. J Autism Dev Disord. 2016;46(4):1368–1378.
  18. Autism and Developmental Disabilities Monitoring (ADDM) Network. Centers for Disease Control and Prevention.
  19. Autism Diagnosis Criteria: DSM-5. Autism Speaks.
  20. Recognizing and Preventing Abuse. Autism Speaks.
  21. The Controversy Around ABA. Child Mind Institute.
  22. What is Autism? National Autism Association.
  23. Early Death in Those with Autism Spectrum Disorder. Psychology Today.
  24. Encouraging Picky Eaters with Autism to Try New Foods. Autism Speaks.
  25. Autism and diet: Food Fact Sheet. The Association of UK Dieticians.
  26. Nutrition and Autism. Autism Speaks.