Autism Prevalence

Determining and Monitoring Autism Prevalence

Autism and Developmental Disabilities Monitoring Network (ADDM)

The Autism and Developmental Disabilities Monitoring (ADDM) Network is a collaborative network of programs funded by the Centers for Disease Control and Prevention (CDC) to estimate and track the number and characteristics of children with Autism Spectrum Disorder (ASD) and other developmental disabilities living in different areas of the United States. In order to provide accurate, population-based estimates of prevalence, ADDM Network sites work with community sources to review health and education records of children living within the geographic area of a participating site during the years under consideration.

Determining and monitoring autism prevalence in San Diego

Over the last 20 years, the CDC has funded ADDM Network sites in 17 different states. California is the most recent award site. Based out of the University of California San Diego's Autism Center of Excellence, the CA site will be focusing on prevalence estimates in San Diego County. Karen Pierce, Ph.D., is the principle investigator of the CA site.

Other current participating sites

• University of Arizona
• University of Wisconsin System
• Johns Hopkins University
• University of Minnesota
• Rutgers, The State University of New Jersey
• University of Arkansas System
• University of Utah
• Vanderbilt University Medical Center
• Washington University in St. Louis

What We've Found

On December 2, 2021, the CDC released the most recent national prevalence reports for children aged 4 and 8 years old. These reports are based on data collected from the eleven different ADDM Network sites in 2018. The ADDM Network is the only collaborative network to track the number and characteristics of children with ASD in multiple communities in the US.

Prevalence in 8-year-olds

The 2021 report found that an estimated 1 in 44 eight-year-old children were identified with ASD. This number is higher than estimates from the last ADDM Network report which found that 1 in 54 8-year-old children were identified with ASD.  Prevalence varied by community and ranged from 1 in 60 in Missouri to 1 in 26 in California. Boys were more than 4 times as likely to be identified with ASD as girls across the network. In 2018, there were no overall differences in the percentage of Asian or Pacific Islander, Black, Hispanic, or White children identified with ASD at either the Network level, or in California, though some communities did have lower percentage of Hispanic children identified with ASD compared to White or Black. Among the 8 year olds with ASD 47% were first evaluated before 36 months of age across the Network and more than half were first diagnosed by 50 months of age (previously 51 months). However, in California, over 54% were first evaluated by 36 months and more than half of the 8 year olds were first diagnosed with ASD by 36 months of age, at least 9 months earlier than any other site in the Network.

Read the full 8 year old prevalence report.

Prevalence in 4-year-olds

The 2021 prevalence report found that an estimated 1 in 59 four-year-old children were identified with ASD. This number is higher than the previous ADDM Network report estimate of 1 in 64. Community estimates ranged widely from 1 in 110 in Utah to 1 in 24 in California. Boys were more than 3 times as likely to be identified with ASD as girls, both across the Network as well as here in California. ASD prevalence estimates by race and ethnicity for 4-year-old children varied among sites with Asian or Pacific Islander, Black, and Hispanic children having higher prevalence than White children. A similar pattern was seen in California. Among the 4 year olds, 72% of children had their first evaluation prior to 36 months (over 74% in California). Four-year-old children were 50% more likely to receive an ASD diagnosis or special education classification by 48 months of age compared to eight-year-olds with California leading the way in early diagnosis for both four and eight year olds.

Read the full 4 year old prevalence report.

Comparing Data Across Sources

The ADDM Network is not alone in the effort to understand how many families are impacted by ASD. Other programs, including the National Survey of Children's Health (NSCH), the National Health Interview Survey (NHIS), the Centers for Medicare and Medicaid Services (CMS), and the US Department of Education (USDE), to name a few, are all working to determine ASD prevalence. Because each program collects data in a different way, the prevalence estimates vary across the different programs. For example, the US Department of Education reports on the number of children who receive special education and related services under the primary disability category for ASD, while CMS data is based on Medicaid billing codes, and both the NSCH and NHIS are based on parent/caregiver report of a professional diagnosis.

The ADDM Network, however, utilizes a comprehensive, multiple source, records-based population surveillance system. Each site works with local health, education, and early intervention providers to determine the number of children with ASD in their community and to understand the characteristics of those children in order to better understand what it means to have an Autism Spectrum Disorder.

The ADDM Network maintains a data visualization tool that can be used to examine, not only the ADDM data, but also data from the other organizations working on prevalence data. Prevalence rates from each organization vary considerably due to how and from whom they collect data.

View the Autism Data Visualization Tool.

Learn more

Learn more about CDC's Learn the Signs, Act Early campaign and how you can track your child's milestones from age 2 months to 5 years.

Questions?

If you or your organization would like more information on how you can be a part of this important work, contact our CDC ADDM Project Manager:

Andrea Grzybowski, M.S.
CDC ADDM Project Manager
agrzybowski@health.ucsd.edu
858-534-6910