How Widespread Is Autism?

Just how many people have autism? What are theories about its causes? Read about them in the second article in a special five-part series on children and autism.

No one knows just how many people have autism.

Estimates range from two to six out of every 1,000 people. This means as many as 1.5 million Americans have some form of autism. The U.S. Department of Education and other governmental agencies say autism is growing at a rate of 10 percent to 17 percent a year. The Autism Society of America estimates the number of people with autism could reach 4 million in the next decade.

Autism is a complex developmental disability appearing in the first three years of life and affects how the person interacts and communicates.

The origin of the disorder is mysterious: Researchers aren't really sure why or how it happens, but they do think there are genetic factors.

The Centers for Disease Control and Prevention (CDC) says it is not sure what accounts for the increasing prevalence of autism: Is it is actually more children that are being affected than ever before, or is it because of growing awareness about the disorder, better ability to diagnose and expanded definitions of autistic disorders?

The disorder affects boys more often than girls. About 80 percent are male.

The CDC's Autism and Developmental Disabilities Monitoring Network (ADDM) reports that as of 2006, 1 in 150, 8-year-old children (6.6 per 1,000) in multiple areas of the United States had an Autism Spectrum Disorder (ASD). ASD is classified as one of several conditions under the autism umbrella such as pervasive developmental disorders (PDD), Asperger's syndrome, Rett's syndrome and childhood disintegrative disorder. This number accounts for the lowest prevalence of ASD in Alabama (3.3 per 1,000 children) and the highest prevalence in New Jersey (10.6 per 1,000 children).

Vaccines at fault?

The CDC says that the weight of evidence indicates that vaccines are not associated with autism. Due to ongoing concerns about this issue, the CDC will continue to study the potential role of vaccines as it strives to identify the biological and environmental causes of autism and other developmental disabilities.

Next: Intervention techniques

Related Articles Autism: A Child in a Lonely World What Is Autism? How Safe Are Vaccines?

External Sources Autism Society of America Cure Autism Now Foundation The National Alliance for Autism Research The Princeton Child Development Institute National Institute of Mental Health Weill Medical College of Cornell University Eden Institute George Washington University in Washington Centers for Disease Control and Prevention, Autism Information Center. Frequently Asked Questions - Vaccines and ASDs. February 7, 2007. Centers for Disease Control and Prevention, Autism Information Center. Frequently Asked Questions - Prevalence. April 4, 2007.

This article was reviewed and updated June 2007.

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