Autism spectrum disorder (ASD) is a complex neurological and developmental disorder that begins early in life and affects how a person acts and interacts with others, communicates, and learns. ASD affects the structure and function of the brain and nervous system. Because it affects development, ASD is called a developmental disorder. ASD can last throughout a person's life.
People with this disorder have problems with:1
- Communication and interaction with other people
- Restricted interests and repetitive behaviors
Different people with autism can have different symptoms. For this reason, autism is known as a spectrum disorder—which means that there is a range of similar features in different people with the disorder.1 This website uses "ASD" and "autism" to mean the same thing.
In giving a diagnosis of ASD, a health care provider will also specify whether the person also has:1
- Intellectual problems, including problems with reasoning or memory
- Language problems, such as problems with speech
- Another medical or genetic condition that is related to or contributes to autism, such as seizures or Fragile X syndrome
In May 2013, a revised version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), the guidelines health care providers use to diagnose different mental health conditions, was released. The DSM-5 made significant changes to how autism is classified and diagnosed.
Now: Under the DSM-5, someone with more severe autism symptoms and someone with less severe autism symptoms both have the same disorder: ASD.
Then: In the previous version of the DSM, ASD was a category and there were four types of autism within the category. These were autistic disorder ("classic" autism), Asperger syndrome (which usually involved milder symptoms, mostly related to social behaviors), childhood disintegrative disorder (in which a child would develop normally for several months or years, then would lose skills related to language, movement and coordination, and other brain functions), and pervasive developmental disorder not otherwise specified (PDD-NOS, or "atypical" autism, which included some, but not all, of the features of classic autism or Asperger syndrome).2
Health care providers no longer use these terms to describe someone with ASD.
The Centers for Disease Control and Prevention tracks the number of people who have ASD. Learn more at https://www.cdc.gov/ncbddd/autism/data.html.