If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

What is autism spectrum disorder?

What is autism spectrum disorder?

How old were you when you first started to play with toys, smile at your family, or say a new word? Some of us did these things very early in life while others took a little longer - every baby grows and changes at their own unique pace. However, they usually follow a similar developmental path and learn skills or reach developmental milestones at about the same time as most other children.
When children don’t reach the milestones for their age group it can be a sign that something is wrong. For example, if a child’s social and communication skills don’t develop at a normal rate, they could have autism spectrum disorder. Autism is a neurodevelopmental disorder that causes a wide range of problems with language, social skills and behavior, which affect the child’s ability to function and lead a normal life.

How do children develop normally?

Before we are born, we receive genetic information from our parents that help to make us who we are. Our genes act like a blueprint for our development and help form the basic architecture of our brain and body. Our physical development usually corresponds with our psychological and behavioral development, which means that as our brain grows, the foundation of our personality, feelings, thoughts, and behavior start to develop and emerge too. For example, as parts of the brain associated with language develop, babies start to babble and form sounds. This process usually happens in a predictable way and parents can expect certain behaviors, traits, and skills at certain times in their child’s life.

What happens when things go wrong?

The brain is extremely vulnerable during pregnancy, infancy, and early childhood. It has trouble handling things like abnormal genes, toxic chemicals, and infections, and is highly responsive to maternal influences like stress and malnutrition. When the brain is influenced by harmful maternal or environmental factors during its early development, its structure, growth, and maturation can change dramatically. Autism spectrum disorder is associated with developmental problems in several different parts of the brain.
Part of the brainNormally deals with...How is it different in the brain of someone with autism?
AmygdalaEmotional responsesEnlarged, aggressive behavior
HippocampusMemoryEnlarged, difficulty learning new inormation
Brain stemPrimitive functions and passing messages between body and cerebral cortexGrows abnormally, sensory problems, especially with boys
Cerebral cortexHigher mental functions, general movement, perception, and behavioral reactionsSmaller, language delays, intellectual deficits
Basal gangliaAutomatic movementSmaller, language delays
Corpus callosumConnects brain hemispheres and allows them to communicateThinner than normal, disrupted connectivity between hemispheres
CerebellumMotor activity, balance, body movements, coordination, and speechAbnormal cells, movement, language and social deficits
NeuronsCells of the brainSmaller, more densely packed, and have shorter, less developed branches in the brain of a person with autism spectrum disorder


The word “spectrum” refers to the fact that the symptoms of autism spectrum disorder can be very different from person to person - some children are severely affected and others only have mild issues. Autism causes problems with communication, social skills, and behavior.
Communication symptoms: problems with language, speech, listening, and comprehension, like:
  • significant delays in learning to speak, or no speech at all
  • speaking too loudly or in an abnormal tone of voice
  • misunderstanding abstract thoughts, sarcasm or humor
  • misunderstanding simple words and sentences
  • abnormal body language
  • trouble beginning or sustaining conversation
  • talking to themselves
  • talking at someone instead of to someone, like going off on a tangent without any response
  • repeating words or questions over and over again
Social symptoms: problems with basic social interaction, like:
  • avoiding or resisting touch or physical affection (like cuddling in childhood and sexual relationships in adulthood)
  • feeling indifferent about being separated from family or parents
  • lacking interest in friendships or social experiences
  • difficulty engaging in play with others
  • difficulty making friends or maintaining relationships with others
  • difficulty understanding the emotions and behaviors of others
  • difficulty maintaining appropriate eye contact or avoiding eye contact all together
  • misreading social cues
  • lacking interest in the world around them
Motor symptoms: problems with behavior and play, like:
  • engaging in compulsive or ritualistic behavior, like twirling, hand flapping, or rocking back and forth
  • resisting change and becoming upset when anything changes
  • throwing tantrums
  • needing strict, constant routines
  • being preoccupied with objects or having obsessions with certain objects
  • spinning or chewing on toys instead of interactively playing with them
  • engaging in self-injurious behaviors because of indifference to pain or extreme temperatures
  • skin picking or head banging
Other symptoms of autism spectrum disorder include:
  • intellectual disabilities, like problems with thinking, judgment, problem solving, planning, or general learning sensory abnormalities, like hating certain sounds, textures, smells or bright lights
  • savantism, or extreme talents and abilities, usually in the areas of memory, music, art, and math
  • mental health problems, like depression, anxiety, OCD, ADHD, insomnia
  • increased susceptibility to infections and illnesses
  • seizures
  • developmental regression, or developing normally to a certain age, then losing all skills

What causes autism spectrum disorder?

Autism does not have a known single cause. Instead, most scientists believe the disorder develops when risk factors interact with one another during pregnancy and early childhood. These factors include:
  • Genetics: there is a strong genetic basis for autism. If you have a sibling with the disorder, you are 2.8x more likely to develop it yourself.
  • Parental age: the risk of autism increases as parents get older. Women over the age of 35 are 1.2 times more likely to have a child with autism spectrum disorder and men over the age of 50 are 2.2 times more likely to have a child with the disorder. This may be because the genes found in sperm and egg cells can mutate as adults age.
  • Maternal health: autism can develop after expectant mothers are exposed to certain illnesses or drugs during pregnancy. For example, infections during pregnancy (like rubella), exposure to psychiatric medication like antidepressants and anti-seizure drugs, and complications during pregnancy and delivery all increase the likelihood that a child will develop autism spectrum disorder.
  • Environmental factors: infants are especially vulnerable to environmental factors because they are still developing. If babies are exposed to toxins during childhood, like pesticides, traffic-related air pollution, cyanide, methylene chloride, methanol, arsenic, or bisphenol-A (BPA) they are more likely to develop autism spectrum disorder.

How common is autism spectrum disorder?

Autism spectrum disorder is present in all racial, ethnic, and socioeconomic groups. Autism is becoming more and more common and scientists are not exactly sure why – some believe that awareness of the disorder has increased rates of diagnosis, while other think there are more children actually developing the disorder. Regardless of the reason, prevalence is rising steadily around the world– about 1% of Americans, 1% of adults from the UK, and 2.68% of children from South Korea have been diagnosed with autism spectrum disorder. In the US, about 1 in every 68 children develop the disorder. Autism is 5 times more common in boys than girls – 1 in every 54 boys and 1 in every 252 girls develops the disorder.

Is autism spectrum disorder preventable?

Because autism spectrum disorder has such a strong genetic basis, it can’t be prevented. However, there are certain changes that can be made to decrease the risk of developing the disorder. For example, prospective mothers should try to minimize potential risks during pregnancy by avoiding alcohol, tobacco or other drugs, choosing nutrient dense foods, washing fruits and vegetables to remove pesticides, taking multivitamins, using stainless steel water bottles instead of plastic bottles, and avoiding prescription medications. They should also get immunized for rubella before trying to get pregnant.
Early diagnosis and intervention is extremely important because it can help young children with autism develop to their full potential and improve their ability to function. Parents should pay close attention to their child’s development and reach out for help as soon as they notice problems. Doctors should also screen children for symptoms when they are between 18 and 24 months old.

How is autism spectrum disorder treated?

Most children with autism are treated by a team of specialists, including psychologists, psychiatrists, school counselors, pediatricians, teachers, speech therapists, occupational therapists and dieticians. The team works together to develop an integrative treatment plan, with the goal of decreasing symptom severity and improving functioning.
  • Early intervention programs are for children under the age of 3 who are having trouble meeting developmental milestones. Specialists focus on helping babies and toddlers learn basic skills like crawling, playing, eating, getting dressed, and talking. These programs include education and support for parents and families.
  • Behavior and communication treatments teach children to express themselves and behave appropriately. Applied Behavior Analysis (ABA) is the most effective treatment for autism spectrum disorder, and uses behavioral principles to understand and increase positive behaviors and decrease negative behavior. ABA therapists help children learn to communicate, be social, take care of themselves, play appropriately, and perform in school. They usually break complex skills down into small, manageable tasks and reinforce the child as they complete each step.
Speech therapy focuses on improving verbal and non-verbal communication skills. Speech therapists teach children with autism about how to produce sounds or the mechanics of speech, how to understand words and sentences, and how to use language socially. They may also work on nonverbal communication like eye contact, hand gestures, and body language, or teach the child to use picture boards.
Occupational therapy helps children function in their home and school environments. Occupational therapists focus on changing responses to sensory experiences like touch or sounds, improving motor like walking and writing and teaching social skills like playing with others.
  • Medications are usually combined with ABA to target specific symptoms: Antidepressants like SSRI’s reduce the frequency and intensity of stereotyped behaviors. They also decrease anxiety, irritability, tantrums, and aggressive behavior.
Antipsychotics like risperidone decrease hyperactivity, irritability, and ritualistic self-harming behaviors like skin picking or head banging.
Stimulants like adderall improve concentration and decrease hyperactivity in children who have mild symptoms of autism spectrum disorder.
Anticonvulsants like carbamazepine decrease seizures.
  • Dietary approaches manage eating-related problems and treat nutritional deficits caused by food selectivity, ritualistic eating, or food sensitivities and allergies. Dieticians help parents identify foods that cause gastrointestinal distress, limit foods that affect symptom severity (like sugar and irritability/hyperactivity), and encourage healthy eating habits.

Consider the following

In 1998, a paper was published that linked the development of autism to childhood vaccines. The research had a huge influence on the public’s perception of vaccines and led to a powerful anti-vaccination movement that was backed by celebrities and activists across the country. Over 10 years later, the article was debunked, retracted, and the original author was stripped of his medical license – an investigation found that he had falsified and manipulated the data used to make his claims. Follow-up studies around the world have confirmed that there is no link between autism and vaccines, but many parents still avoid vaccinating their children, which puts them and others at risk for serious and sometimes deadly illnesses like measles and mumps.

Want to join the conversation?

  • duskpin ultimate style avatar for user Spoonie
    What does the author of this article think of the controversy surrounding ABA therapy, and the viewpoints of some autistic adults who had ABA as children?
    (12 votes)
    Default Khan Academy avatar avatar for user
    • leafers ultimate style avatar for user Adrien Agreste
      The issue is that oftentimes, therapy is trying to change things about an autistic individual that cannot be changed, akin to conversion therapy for homosexuals. Many autistic graduates of these "therapy" programs have come out of it less able to cope with the world, and with anxiety disorders such as PTSD. Sometimes an autistic individual can pretend to be neurotypical, but often this causes more harm to them than good, as it causes them to have to use much of their brain capacity in mechanically erasing their thoughts and feelings and conforming to the world, whereas simply being accepted in the world, much akin to the way that we don't force people who use wheelchairs to walk, would be better for their general well being. The very existence of these therapies masks the ways that we fail to accommodate people with autism in the world and places the burden on the autistic individual to conform, rather than on us to accommodate.
      (9 votes)
  • duskpin seedling style avatar for user Gemma Buske
    I have a kid in my class with Autism and I find it hard to deal with him..... what should I do?
    (2 votes)
    Default Khan Academy avatar avatar for user
  • starky sapling style avatar for user sunnylovesminecraft
    What do autism vaccinations do?
    (0 votes)
    Default Khan Academy avatar avatar for user
    • duskpin ultimate style avatar for user Nathan William Brown
      There are no vaccinations for Autism. There has been controversy from unscientific articles linking childhood vaccines to Autism which has lead to some parents not getting their children vaccinated. These "anti-vaccine" have lead to a resurgence in many nearly eradicated childhood diseases, despite no evidence ever showing a positive link between Autism and Vaccines.
      (10 votes)
  • blobby green style avatar for user Bad Username
    Autism is a complex issue and I really don't think this article does much justice to it.
    There is a growing social movement of autistic people who think that they are neurodivergent and different cognitively rather than having a disorder. If autism is a disorder how come autistic people can have any level of intelligence and there are also correlations between autism and hyperlexia, strong memory, honesty and loyalty, attention to detail, visual and spatial skills and mathematical and logical skills.
    If you are training to become a doctor or are interested in autism I beg you learn about autism from autistic people themselves. Why study autistic people (or any group for that matter) when you can just ask them?
    Look up #actually autistic if you're curious.
    (2 votes)
    Default Khan Academy avatar avatar for user
  • starky seedling style avatar for user Anastasia Rightler
    In the fourth paragraph, you talk about how it is believed that different environmental factors can influence whether or not a child could develop autism. What are the likely hoods for a chemical research scientist to give birth to an autistic child compared to a mother that isn't a research scientist?
    (1 vote)
    Default Khan Academy avatar avatar for user
    • aqualine ultimate style avatar for user Ancient Warrior
      The thing about autism is that the symptoms are different in every child, which make it hard to pinpoint the cause. However, the environment could play a part, and to answer your question, the answer would vary. If the mother who is a chemical research scientist continues to work while pregnant and exposes herself to the chemicals she works with, this could affect her child's likelihood of autism, but it depends on the chemicals she works with.
      (2 votes)
  • duskpin ultimate style avatar for user Bob Bruer
    I am very intrigued by mention of an association between ASD and [enlarged hippocampus + difficulty learning new information] (spelling error btw: "f" missing from "information" in actual table).

    The amygdala being enlarged all makes sense. The enlarged hippocampus also makes sense physically ... but the resulting dysfunction in "learning new" does not. Does the research perhaps more clearly show "learning new" rate is appropriate or even above-average, but the type of "new information" being learned is rather outside the norm? For example, the Dustin Hoffman character in Rainman was learning prodigious amt's of stuff, albeit not the stuff most necessary for thriving in the social setting he lived in.
    (1 vote)
    Default Khan Academy avatar avatar for user
    • leaf green style avatar for user jpeters6432
      The hippocampus is what allows us to mentally travel away from the present moment. Obviously, this is very helpful when you want to recall a memory or imagine something that could happen. However, too much of this imagining can make it difficult to learn from what is happening in the present moment. This is how I make sense of an enlarged hippocampus leading to learning difficulties.
      (3 votes)
  • marcimus pink style avatar for user acuphysio108
    How come neurofeedback is not included in your treatment option. It is recommended by american academy of pediatric association.
    (1 vote)
    Default Khan Academy avatar avatar for user