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Is Autism Increasing?

Autism may be more common than previously thought. In fact, it may even affect as many as one in 150 U.S. children, according to a recent report by the Centers for Disease Control and Prevention (CDC).

Whether this is actually the case remains to be seen. Experts point to other factors for the increased reporting of autism and the need for further research.

The new CDC report, however, is the largest and most comprehensive summary of prevalence data yet, combining data from two separate studies conducted in fourteen states. The study aimed to estimate how widespread autism spectrum disorder (ASD) is among American children. ASD is a term that incorporates not only the classical form of autism, but also closely related disabilities. ASD includes: Pervasive Developmental Disorder—Not Otherwise Specified (PDD-NOS), which contains several features that resemble autism, but may not be as severe; Rett’s syndrome, which affects girls and is genetic with a neurological component; and Asperger’s syndrome, referring to individuals with some autistic symptoms, but with intact language abilities. Some physicians include other disorders under the ASD umbrella as well, including Childhood Disintegrative Disorder, which refers to children who appear to develop normally for the first few years of life, but then regress suddenly and dramatically with loss of speech and the development of autistic characteristics. Often, the terms for the classical form of autism and ASD are now used interchangeably.

Six sites evaluated the prevalence of ASD in 2000, and another eight sites looked at the prevalence of ASD in 2002. ASD cases were identified through review of health and education records of eight-year-old children, as research had shown most children had been diagnosed by that age.

The results showed an average of 6.7 children out of 1,000 had an ASD in the six communities assessed in 2000, and an average of 6.6 children out of 1,000 had a form of autism in the fourteen communities included in the 2002 study.

The authors concluded that the study “confirms that ASDs are more common than previously thought and are conditions of urgent public health concern.”

Although the study reports higher rates of autism than in previous years—6.6 to 6.7 per 1,000 children as compared to 5.5 per 1,000 from last year—it doesn’t necessarily mean the incidence of autism is increasing.

Wider access to records and better data may be one reason the estimates have increased, but experts also suggest that an increase in awareness of these disorders and a broadening of the ASD diagnosis to a wider range of symptoms may have contributed to the higher estimate.


Some interesting findings include the wide discrepancy between autism rates between the states analyzed. For instance, only 3.3 per 1,000 children in Alabama were diagnosed with a form of ASD compared with 10.3 per 1,000 in New Jersey. The cause of the variation between states was unknown, but may be due to better record keeping in some states and inability to locate records in others. Environmental impact could be another reason as well.

Another finding is that ASD is more common in boys than in girls and that most developmental concerns are noticed before three years of age.

“Finally, we can end the debate on the prevalence of autism in our nation and focus on getting the services and supports the families need,” states Lee Grossman, president and CEO of the Autism Society of America, in a press release. “Autism is a treatable lifelong condition that affects tens of millions of Americans today. It is time to aggressively address this national health crisis.”

Because scientists do not yet know what causes autism, and there is no biological test for it, physicians must rely on behavioral clues. This can make diagnosis more difficult than other diseases, such as cancer, where a biopsy can provide definitive evidence of disease. (For more information, see “Autism Behavioral Checklist” and “Autism Early Detection.”

Genes and environment most likely play a role in disease development and many advocates point to the possibility of vaccines causing autism. To date, there has been no scientific evidence backing up this claim.

Although the study did not look at the causes of ASDs, the CDC’s Centers for Autism and Development Disabilities Research and Epidemiology Network is planning on doing “a multi-state study to help identify factors that may put children at risk for ASDs.”

While the study is compelling, and autism and ASD is a serious issue for our nation, it’s important to remember that the CDC collected data on only fourteen states. It cannot provide a national estimate. Only future research from all states can do that.

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