About Autism Spectrum Disorder

Key points

  • Autism spectrum disorder (ASD) is a developmental disability caused by differences in the brain.
  • Some people with ASD have a known difference, such as a genetic condition. Other causes are not yet known.
  • Scientists believe there are multiple causes of ASD that act together to change the most common ways people develop. We still have much to learn about these causes and how they impact people with ASD.
  • Early intervention services can greatly improve the development of a child with ASD.
Physiotherapist pediatrician doctor doing exercises with her patient


People with ASD may behave, communicate, interact, and learn in ways that are different from most other people. There is often nothing about how they look that sets them apart from other people. The abilities of people with ASD can vary significantly. For example, some people with ASD may have advanced conversation skills whereas others may be nonverbal. Some people with ASD need a lot of help in their daily lives; others can work and live with little to no support.

ASD begins before the age of 3 years and can last throughout a person's life, although symptoms may improve over time. Some children show ASD symptoms within the first 12 months of life. In others, symptoms may not show up until 24 months of age or later. Some children with ASD gain new skills and meet developmental milestones until around 18 to 24 months of age, and then they stop gaining new skills or lose the skills they once had.

As children with ASD become adolescents and young adults, they may have difficulties developing and maintaining friendships, communicating with peers and adults, or understanding what behaviors are expected in school or on the job. They may come to the attention of healthcare providers because they also have conditions such as anxiety, depression, or attention-deficit/hyperactivity disorder (ADHD), which occur more often in people with ASD than in people without ASD.

April is Autism Acceptance Month join us aw we #celebrateDifferences!
Join us in April, during Autism Acceptance Month, as we celebrate differences

Signs and symptoms

People with ASD often have problems with social communication and interaction, and restricted or repetitive behaviors or interests. People with ASD may also have different ways of learning, moving, or paying attention. These characteristics can make life very challenging. It is important to note that some people without ASD might also have some of these symptoms.

As a parent, you already have what it takes to help your young child learn and grow. CDC has developed materials to help you track your child's developmental milestones and share that progress, or any concerns, with your child's doctor at every check-up.

Risk factors

There is not just one cause of ASD. Many different factors have been identified that may make a child more likely to have ASD, including environmental, biologic, and genetic factors.

Although we know little about specific causes, the available evidence suggests that the following may put children at greater risk for developing ASD:

  • Having a sibling with ASD
  • Having certain genetic or chromosomal conditions, such as fragile X syndrome or tuberous sclerosis
  • Experiencing complications at birth
  • Being born to older parents

CDC is currently working on one of the largest US studies to date on ASD. This study, called the Study to Explore Early Development (SEED), was designed to look at the risk factors and behaviors related to ASD. CDC is now conducting a follow-up study of older children who were enrolled in SEED to determine the health, functioning, and needs of people with ASD and other developmental disabilities as they mature.

Screening and diagnosis

Diagnosing ASD can be difficult since there is no medical test, like a blood test, to diagnose the disorder. Doctors look at the child's behavior and development to make a diagnosis.

ASD can sometimes be detected at 18 months of age or younger. By age 2 years, a diagnosis by an experienced professional can be considered reliable.1 However, many children do not receive a final diagnosis until they are much older. Some people are not diagnosed until they are adolescents or adults. This delay means that people with ASD might not get the early help they need.

Two children playing with blocks during an evaluation
Contact your child's doctor if you have any concerns about your child's development.


Current treatments for ASD seek to reduce symptoms that interfere with daily functioning and quality of life. ASD affects each person differently, meaning that people with ASD have unique strengths and challenges and different treatment needs.2 Treatment plans usually involve multiple professionals and are catered to the individual.

What CDC is doing

Promoting early identification of ASD

We naturally think of a child's growth as height and weight, but from birth to 5 years, a child should reach milestones in how they play, learn, speak, act, and move. A delay in any of these areas could be a sign of ASD or other developmental disability.

Through the Learn the Signs. Act Early. program, CDC and its partners aim to improve early identification of children with ASD and other developmental disabilities by promoting developmental monitoring, so children and families can get the services and support they need.

Did you know?‎

You can download CDC's Milestone Tracker mobile app.

Understanding risk factors and causes of ASD

Understanding the risk factors that make a person more likely to develop ASD will help us learn more about the causes. CDC is currently funding and working on one of the largest US studies to date, called Study to Explore Early Development (SEED).

SEED will help identify factors that may put children at risk for ASD and other developmental disabilities. SEED is a multi-year study being conducted at six sites and a data coordinating center, called the Centers for Autism and Developmental Disabilities Research and Epidemiology (CADDRE) network.

Determining how many people have ASD

There continue to be many children living with ASD who need services and support, both now and as they grow into adolescence and adulthood.

By studying the number of people identified with ASD over time, we can find out if the number is rising, dropping, or staying the same. We can also compare the number of children with ASD in different areas of the country and different groups of people. This information can help us look for causes of ASD.

CDC's Autism and Developmental Disabilities Monitoring (ADDM) Network has been estimating the number of 8-year-old children with ASD in the United States since 2000. ASD occurs in all racial, ethnic, and socioeconomic groups. It is more than 4 times more common among boys than among girls.


If you’re concerned

Research shows that early intervention services can greatly improve a child's development.34 In order to make sure your child reaches their full potential, it is very important to receive services as soon as possible. Contact your child's doctor if you think your child might have ASD or if you have any other concerns about the way your child plays, learns, speaks, or acts.

Referral to a specialist

If you are still concerned, ask the doctor for a referral to a specialist who can do a more in-depth evaluation of your child. Specialists who can do a more in-depth evaluation and make a diagnosis include

  • Developmental pediatricians (doctors who have special training in child development and children with special needs)
  • Child neurologists (doctors who work on the brain, spine, and nerves)
  • Child psychologists or psychiatrists (doctors who know about the human mind)

Free evaluations

At the same time, call your state's public early childhood system to request a free evaluation, sometimes called a Child Find evaluation, to find out if your child qualifies for intervention services. You do not need to wait for a doctor's referral or a medical diagnosis to make this call. Where to call for a free evaluation from the state depends on your child's age.

If your child is not yet 3 years old

  • Contact your local early intervention system.
  • You can find the right contact information for your state by calling the Early Childhood Technical Assistance Center (ECTA) at 919-962-2001.
  • Or visit the ECTA website.

If your child is 3 years old or older

  • If your child is 3 years old or older, contact your local public school system.
  • Even if your child is not yet old enough for kindergarten or enrolled in a public school, call your local elementary school or board of education and ask to speak with someone who can help you have your child evaluated.
  • If you're not sure who to contact, call the ECTA at 919-962-2001.
  • Or visit the ECTA website.
  1. Lord C, Risi S, DiLavore PS, Shulman C, Thurm A, Pickles A. Autism from 2 to 9 years of age. Arch Gen Psychiatry. 2006;63(6):694-701.
  2. Hyman SL, Levy SE, Myers SM; COUNCIL ON CHILDREN WITH DISABILITIES, SECTION ON DEVELOPMENTAL AND BEHAVIORAL PEDIATRICS. Identification, Evaluation, and Management of Children With Autism Spectrum Disorder. Pediatrics. 2020;145(1):e20193447.
  3. Handleman, Jan S., and Sandra L. Harris, eds. Preschool education programs for children with autism. Austin, TX: Pro-Ed, 2001.
  4. National Research Council. Educating Children with Autism. National Academies Press, 2001.