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Is Autism on the Rise?


Updated May 12, 2009

Is There an Autism Epidemic?:

When many of us were growing up, autism was rarely heard of. Today, everyone seems to be or know someone with an autistic child. Certainly, the numbers of children diagnosed with autism has surged in the past decade. But there's tremendous disagreement about whether the increase in diagnoses is truly reflective of more autism -- or just reflective of more diagnoses.

A Brief History of Autism Statistics:

Autism was first described as a unique disorder in the 1940s. In the early 1990s, autism diagnoses began to soar. In the 10 years between 1993 and 2003, the number of American schoolchildren with autism diagnoses increased by over 800%. In 2006, the CDC noted a slight decrease in the number of new cases diagnosed.

Changes in the Diagnostic Criteria:

In 1991, the Autism Diagnostic Interview was published. This was the first generally recognized tool for diagnosing autism. In 1992, the American Psychiatric Association released the Diagnostic and Statistical Manual (DSM-IV), which refined diagnostic criteria for autistic disorder. Autism became a spectrum disorder; in essence, it became possible for someone to be very autistic or mildly autistic.

Changes in the IDEA Law:

Up until 1990, autism was not included in legislation aimed at guaranteeing an education to individuals with handicaps. In 1990, the new Individuals with Disabilities Education Act added autism to its list of categories of children and youth served under the act. The new law also added transition services and assistive technologies to its requirements. Autism had never been tracked as an educational statistic before 1990. Since 1990, the incidence of autism in schools has risen dramatically.

Vaccines and Autism:

Thimerosal, a mercury-based preservative, was first added to vaccines in the 1930s. By the 1990s, babies and young children were receiving multiple thimerosal-containing vaccines. A passionate group of doctors and parents, convinced that thimerosal was resonsible for a growing autism rate, pushed hard to have the preservative removed. In 1999, thimerosal was removed from most vaccines. Despite many studies, the CDC states they there is no connection between autism and thimerosal.

The 2006 CDC Research:

In 2006, the CDC conducted a large-scale survey to better understand the prevelance of autism in the United States. They found that about 300,000 individuals -- or one in every 166 people -- had been diagnosed on the autism spectrum. They also found that there was a slight decrease in the incidence of autism diagnoses since 1999.

Why Did Autism Diagnoses Soar?:

Clearly, there are two schools of thought on this issue. On the one hand are those who say that the change in diagnostic criteria, combined with new school statistics and rising awareness of autism all created an apparent (but not real) epidemic. On the other hand are those who say that thimerosal caused the epidemic -- and the removal of thimerosal from vaccines means the beginning of the end of the epidemic.

Are Autism Diagnoses Still on the Rise?:

There has been a slight decrease in the number of annual autism diagnoses. This change, in some researchers' view, is highly signficant -- and goes a long way toward proving the thimerosal theory. Dr. Robert Davis, director at the immunization safety group at the CDC, however, says the change is not statistically significant, and “[cannot]really be taken to provide any evidence one way or the other."


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