Is It A Rise In Autism, Or Diagnosis?
Posted by Phoenix Woman on January 17, 2009
For many years, the medical community has held that the “autism epidemic” claimed to exist by anti-vaccination activists is far more likely to be a rise in the diagnosis of autism than anything else. A recent UC Davis study, much touted by the anti-vaccinationists as proof that autism rate rises can’t be explained by increased diagnosis, doesn’t exactly say what they claim it does, as Steve Novella notes:
The key to putting this study into context is the phrase “other artifacts”. This study did not control for all possible artifacts resulting in higher diagnosis rates. Specifically, it did not address surveillance, which is likely the dominant factor. It also did not control for shifting diagnosis. In other words, 20 years ago a child may have been diagnosed with a non-specific speech disorder, and today they would be diagnosed with autism, so-called diagnostic substitution as was found by Bishop in 2008.
Another factor is that physicians, teachers, and parents have increased awareness not only of the symptoms but of the autistic label. How many parents who notice that their child is socially withdrawn are going to seek out services or medical attention?
This study did nothing to assess these potentially huge factors. So what this study really did was account for 10% of the increase in autism diagnosis. But it did not show anything about the other 90%, nor rule out the leading contenders for diagnostic artifact. I will add it to my list of references on this question, but it certainly does not overturn all the prior studies listed.
Meanwhile, another study, also using California data, showed that even as the diagnosis rate of autism has risen in California, the overall percentage of kids getting special education has remained unchanged. This strongly suggests, as medical professionals have long held, that conditions are increasingly being diagnosed as autism spectrum disorder when twenty or even ten years ago they might have been diagnosed as, say, schizophrenia –which often was used in the past as a catchall diagnosis and which a 1995 study showed was wrongly diagnosed 35% of the time.
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