Explaining the rise in the autism rate

A recent report stating that one in 50 school children carries an autism diagnosis appears to confirm anecdotal evidence that we are experiencing an increase in the autism rate.

But there are a number of things that should be considered in a discussion of these findings — and leading that discussion should be methodology.

These new data from the CDC’s National Center for Health Statistics (NCHS) are culled from a 2011-2012 survey of parents who were asked about autism spectrum diagnosis among their children ages 6 to 17.

A year ago the CDC’s Autism and Developmental Disabilities Monitoring (ADDM) Network, which based its findings on review of school and medical records and limited its scope to data on 8-year-olds, put the autism rate at 1 in 88.

The ADDM used records from 2008 in its analysis, and it concluded that the rate represented a relative increase of 23% from 2006 and 72% from 2002.

Two different reports from two different entities within the CDC using two different methodologies for data collection — yet the take-home message is the same: more and more children are being diagnosed with autism.

And the authors of the NCHS report point out that it is the prenatal period that is “the key exposure window for ASD risk factors,” which, they say, makes it unlikely that changes in autism prevalence among school children “reflect ‘true’ increases in susceptibility to the condition at these ages.”

What does appear to be happening, the NCHS researchers wrote, is that more children with mild autism symptoms are being identified and formally diagnosed.

Given the greater awareness of autism among both physicians and parents and improved diagnostic techniques — there is now evidence that autism can be diagnosed as early as 18 months — the evolving scenario is likely to include more evidence of an increase in prevalence at least in the near term.

Moreover, autism diagnosis rates will also change with the implementation of DSM-5, which will be unveiled at the American Psychiatric Association meeting this May.

As it now stands with DSM-IV there are four autism spectrum disorders, all of which will be compressed into a single diagnosis with additional specifiers.

That change has already been widely criticized by those in the autism community, who claim it will make it more difficult for some children to access services, but at the same time move those with Asperger’s syndrome into an autism diagnosis.

It is difficult to gauge the impact the DSM-5 change will have on prevalence, although it is tempting to take the cynical view and say it will contribute to a leveling out of the increase — especially given the concern about the lifetime costs of autism.

Sanjay Gupta is editor, The Gupta Guide at MedPage Today, where this article originally appeared, and chief medical correspondent, CNN.

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