Autism spectrum disorders (ASDs) are a group of developmental disabilities that can cause significant social, communication and behavioral challenges. People with ASDs handle information in their brain differently than other people.

ASDs are “spectrum disorders.” That means ASDs affect each person in different ways, and can range from very mild to severe. People with ASDs share some similar symptoms, such as problems with social interaction. But there are differences in when the symptoms start, how severe they are, and the exact nature of the symptoms.

There are three different types of ASDs:

Autistic Disorder (also called “classic” autism) This is what most people think of when hearing the word “autism.” People with autistic disorder usually have significant language delays, social and communication challenges, and unusual behaviors and interests. Many people with autistic disorder also have intellectual disability.

Asperger Syndrome. People with Asperger syndrome usually have some milder symptoms of autistic disorder. They might have social challenges and unusual behaviors and interests. However, they typically do not have problems with language or intellectual disability.

Pervasive Developmental Disorder – Not Otherwise Specified (PDD-NOS; also called “atypical autism”). People who meet some of the criteria for autistic disorder or Asperger syndrome, but not all, may be diagnosed with PDD-NOS. People with PDD-NOS usually have fewer and milder symptoms than those with autistic disorder. The symptoms might cause only social and communication challenges.

ASDs begin before the age of 3 and last throughout a person’s life, although symptoms may improve over time. Some children with an ASD show hints of future problems within the first few months of life. In others, symptoms might not show up until 24 months or later. Some children with an ASD seem to develop normally until around 18 to 24 months of age and then they stop gaining new skills, or they lose the skills they once had.

A person with an ASD might:

  • Not respond to their name by 12 months
  • Not point at objects to show interest (point at an airplane flying over) by 14 months
  • Not play “pretend” games (pretend to “feed” a doll) by 18 months
  • Avoid eye contact and want to be alone
  • Have trouble understanding other people’s feelings or talking about their own feelings
  • Have delayed speech and language skills
  • Repeat words or phrases over and over (echolalia)
  • Give unrelated answers to questions
  • Get upset by minor changes
  • Have obsessive interests
  • Flap their hands, rock their body, or spin in circles
  • Have unusual reactions to the way things sound, smell, taste, look, or feel

Learn more about ASD at CDC.gov.