Researchers, policy makers, and parents trying to untangle the causative factors for surging Autism diagnosis may have just had another knot of confusion land in their laps. Researchers at Columbia University recently analyzed autism cases handled by the Department of Developmental Services in the state of California, which saw a staggering 636% increase in autism diagnoses between 1997 and 2003. Courts and researchers have put to rest the erroneous health-fiction that autism is increasing because childhood vaccinations are on the rise. But does this represent an epidemic of new Disease, diagnostic criteria catching up with a wide-spectrum disorder, or over-diagnoses? It’s not clear, though researchers do not suspect it’s the latter. What is fascinating is the trend that they uncovered.

It turns out that proximity to another child who has already been Diagnosed with autism significantly increases other children’s chances of being diagnosed. Children living within 250 meters of another child already diagnosed with autism are 42% more likely to also be diagnosed with the condition. Living 250 to 500 meters away reduced the likelihood to a still-noteworthy 22%. Since environmental factors were ruled out, the conclusion is that proximity breads awareness of the disease among parents, as well as a better understanding of available diagnostic and support services.

Its hard to know whether this study is good news or bad news. On the one hand, if there’s an epidemic of un-diagnosed autism, its great that parents are able to help each other identify and manage the condition. On the other hand, if the condition is ill-defined, and subject to over-diagnoses in cases where specialists feel pressured to appease insistent parents, it could signal a troubling trend. Without having some knowledge of the true underlying prevalence of disease, its impossible to know which one it is.

In the meantime it’s a fascinating study in the sociology of disease diagnoses. Do you find it surprising?

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