Is Autism Increasing in the USA?

We live in an age in which we’re bombarded with information. As any savvy consumer of information knows, the credibility of information found on the Internet is not guaranteed. We read about theories linking autism to vaccines, about “cures” for autism, and about how the number of cases of autism has grown over recent years.

So, if it seems like you hear a great deal about autism now, that’s both because of the media saturation regarding Autism Spectrum Disorders (ASDs) and because more children are being diagnosed with ASDs now than ever before.

But just because we hear more about autism and an increase in diagnoses, does that mean that ASDs are on the increase in the United States? Or are more children simply being diagnosed with this complex disorder?

Likely the answer is somewhere in between. Autism is not a new disorder: while it has probably been around for centuries, it was not given a name until 1943, according to the Centers for Disease Control and Prevention (CDC). Since the disorder was first named in the middle of the last century, the criteria used to diagnose ASDs have changed many times. There is no medical test for ASDs, so diagnosis is made by observing behavior and symptoms in those affected.

The CDC reports that about 17 percent of children under age 18 are affected by a behavioral, developmental, or learning disability, and that the incidence rate for ASDs is as high as 1 in 150 children. These figures make ASDs the fastest growing developmental disorder in the United States and a disorder more prevalent that many other childhood diseases or disabilities.

The American Academy of Pediatrics (AAP) argues that the reason ASDs seem more common now than they were once thought to be is related to a number of factors: broader diagnosis criteria, increased public and professional awareness of symptoms, and, perhaps, a “true rise in prevalence.” As for one possible cause of ASDs, the AAP states that “sufficient evidence now suggests that vaccines and thimerosal are not likely responsible for the apparent rise in prevalence” of ASDs.

Yet, at least in California, the numbers are increasing: from 205 cases in 1990 to more than 3,000 in 2006. A recent study by researchers at the MIND Institute at the University of California-Davis has found that, while factors such as broader diagnosis criteria and increased awareness of ASDs do contribute to this increase, they do not fully explain the increase. The study found that “Younger ages at diagnosis, differential migration, changes in diagnostic criteria, and inclusion of milder cases do not fully explain the observed increases.”

While known causes of ASDs have not been determined, the MIND Institute study suggests that further investigation of possible environmental factors, as well as study of gene-environment interactions, are in order.

So is autism on the rise in the US? The number of diagnoses is, and yet more investigation is needed to determine whether the increase is related to an increased awareness or to a true rise in the number of children affected.

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