HOMEPAGE > UNDERSTANDING AUTISM > Risk factors
Risk factors
  • There is not just one cause of ASD. There are many different factors that 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 U.S. 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 with 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.
  • How Often ASD Occurs?

    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.