What Is Autism Spectrum Disorder?

Autism spectrum disorder (ASD) is a disability that affects development. The word spectrum refers to the range of symptoms and their severity.

Kids with ASD have problems with social skills, language, communication, and behavior. They may behave differently or repeat the same activities over and over again, like touching the same objects or flipping them repeatedly.

Not all children with ASD have the same problems or behaviors.

The usual signs of ASD usually show up when a child is between 2 and 3 years old, but experts think it begins much earlier, when the brain is starting to develop.

What Is the Autism Spectrum?

In the past, experts talked about several disorders as subtypes of autism. The American Psychiatric Association decided to simplify it and call all of them “autism spectrum disorder.”

The spectrum has a wide range. People who are “on the spectrum” could have very different abilities and experiences. Some people with ASD also have special skills in specific areas like math, music, or art.


There are common signs of the disorder, and a child with ASD might show any of the following behaviors:

  • Has trouble relating to others
  • Avoids eye contact
  • Prefers to be alone
  • Dislikes being embraced
  • Repeats words, phrases, or actions
  • Has trouble expressing needs and emotions
  • Doesn’t get signals from body language, tone of voice, and expressions
  • Needs routines
  • Is sensitive to smell, taste, or sound


Experts don’t fully understand all of the causes of autism spectrum disorder. It seems to be genetic, mostly. And it usually involves more than one gene, so it’s complicated.

For instance:

  • A person is more likely to be on the spectrum if a brother, sister, or parent is. But it doesn’t always run in families.
  • About 10% of kids with ASD have a form of genetic disorder such as Down syndrome and fragile X syndrome.

Some prescription medicines taken during pregnancy have been linked to ASD. But they aren’t proven to cause the condition.

WebMD Medical Reference Reviewed by Renee A. Alli, MD on November 12, 2018



The American Speech-Language-Hearing Association (ASHA): “Autism (Autism Spectrum Disorder).”

National Institutes of Health: “Autism Spectrum Disorder.”

CDC: “Facts About ASD.”

Autism Speaks: “What Is Autism?” “Asperger Syndrome,” “PDD-NOS.”

Autism Support of West Shore: “Defining Autism.”

© 2018 WebMD, LLC. All rights reserved.