What Is Autism?
Autism is a lifelong neurodevelopmental condition that can affect communication, social interaction, behavior, interests, and everyday experiences. Each autistic person has an individual combination of strengths, preferences, challenges, and support needs.
Based on NIMH · CDC · All sources · Checked November 3, 2026
What is autism spectrum disorder?
Autism spectrum disorder (ASD) is a neurological and developmental disorder that affects how people interact with others, communicate, learn, and behave. Although autism can be diagnosed at any age, it is described as a “developmental disorder” because symptoms generally appear in the first two years of life.
The three areas providers look for
According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), the guide health care providers use to diagnose developmental disorders, people with autism often have:
Social communication & interaction
Differences in how a person communicates and interacts with other people.
Restricted interests & repetitive behaviors
Focused interests, repeated actions, and a strong need for routine.
Effect on daily life
Characteristics affect how a person functions at school, at work, and in other areas of life.
The three areas health care providers look for, as described in the DSM-5. Source: NIMH.
Why it is called a spectrum
Autism is known as a “spectrum” disorder because people with autism have a range of characteristics, needs, strengths, and challenges. Learn more about the spectrum.
Who can be autistic?
People of all ages, races, ethnicities, sexes, and economic backgrounds can be diagnosed with autism. Although autism can be lifelong, treatments, services, and supports can improve a person’s health, well-being, and daily functioning.
What causes autism?
Researchers do not know the primary causes of autism, but studies suggest that a person’s genes and aspects of their environment may affect development in ways that lead to autism. Some factors associated with an increased likelihood of autism include:
- Having a sibling with autism
- Having older parents
- Having certain genetic conditions, such as Down syndrome or Fragile X syndrome
- Having a very low birth weight
Not everyone who has these factors will develop autism.
Sources
Adapted from the National Institute of Mental Health, “Autism Spectrum Disorder,” revised 2025. Our website’s presentation does not imply NIMH endorsement.
This website provides general educational information. It does not diagnose autism or replace individualized medical, developmental, psychological, or educational advice. Screening is not diagnosis.
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