What We've Learned about

• An average of 1 in 110 children have an autism spectrum disorder (ASD). This finding reflects data collected by CDC's Autism and Developmental Disabilities Monitoring (ADDM) Network in multiple communities throughout the U.S. during 2006.

Estimates are based on health and education records from participating communities, which includes eight percent of the U.S. population of eight year olds. All children in the studies were eight years old because previous research has shown that most children with an ASD have been identified by this age for services.

• The average total ASD prevalence in 2006 (children born in 1998) was 9.0 per 1,000 children, which translates to 1 in 110 children.
• More Information All ten communities participating in both the earlier 2002 and 2006 study years observed an increase in identified ASD prevalence ranging from 27 percent to 95 percent, with an average increase of 57 percent.
• No single factor explains the changes in identified ASD prevalence over the time period studied. Although some of the increases are due to better detection, a true increase in risk cannot be ruled out.
• Increases were found among boys in nine communities and among girls in four communities. ASD prevalence was 4 to 5 times higher for boys than for girls. These estimates report that one in 70 boys and one in 315 girls have an ASD. The average increase for boys was 60% while the average increase for girls was 48%.
• Data show a similar proportion of children with an ASD also had signs of intellectual disability than in the past, averaging 44% in 2004 and 41% in 2006.
• Concerns regarding development before the age of 24 months were noted in the evaluation records of most children, but the average age of earliest ASD diagnosis was much later at 54 months.

Understanding Risk Factors and Causes

In addition to updating prevalence estimates of ASDs, CDC is currently enrolling for the Study to Explore Early Development (SEED) to help identify factors that may put children at risk for ASDs and other developmental disabilities. SEED is studying potential risk factors that may be related to genes, health conditions and other factors that affected the mother's pregnancy and the child's first few years of life.

Recognizing the Early Signs of ASDs

We naturally think of a child's growth as height and weight, but from birth to 5 years, a child should reach milestones in how he or she plays, learns, speaks and acts. A delay in any of these areas could be a sign of ASD or other developmental disability.

Through the "Learn the Signs. Act Early." program, CDC and its partners work together to educate parents about child development, including early warning signs of ASDs and other developmental disorders, and encourage developmental screening and intervention.

About Autism

ASDs are a group of developmental disabilities causing major social, communication and behavioral challenges with symptoms typically present before age 3 years. ASDs include autistic disorder, pervasive developmental disorder- not otherwise specified (PDD-NOS) and Asperger syndrome. Studies show that early identification and intervention can improve long term outcomes.