A March 2012 report from the Centers for Disease Control and Prevention (CDC) showing that the prevalence of autism spectrum disorders (ASDs) in the United States has risen by 78% since 2002, along with a controversial Diagnostic and Statistical Manual of Mental Disorders, fifth edition, (DSM-5) proposal to revise diagnostic criteria, have drawn recent attention to ASDs. Medscape spoke with Fred Volkmar, MD, Chair of the Child Study Center at the Yale University School of Medicine and Chief of Child Psychiatry at Yale-New Haven Children's Hospital, about the implications of these 2 important issues.
Autism Up 78%: Reality or Increased Diagnosis?
Medscape: Hello Dr. Volkmar. A new CDC report shows a 78% increase in ASD prevalence since 2002. How do you explain these findings? Do the data represent an actual increase, or rather increased diagnosis?
Dr. Volkmar: A long story made short: There are a number of possible factors that could account for an apparent increase that might or might not be real. Of course, one possibility is that to some extent there might be a real increase. However, while that can't be ruled out, it is probably a less likely possibility.
There is more public awareness of autism. There's more attention. There's often a pressure on the part of parents for an autism spectrum label. Often there's a slippery slope equating autism with autism spectrum and there's often a push for getting the label for school services -- sometimes quite appropriately and sometimes less so. This is a problem that sometimes has been referred to as diagnostic substitution in the literature: having multiple possible labels and picking the one that will get you the most services. All of those things factor into it. And there is some reason to think that there could, at least in theory, be some potential for the actual increase based on genetic studies. Usually in terms of seeing such a fast increase, you would think this is going to be more about method than reality. But again, it's hard to know.
In terms of the CDC paper, we would have a better handle on all this had they broken it down by diagnostic categories. The great beauty of the report is that it involved multiple sites around the country. The downside is there's not quite enough diagnostic detail -- how many of the diagnoses were spectrum and how many classical autism? I think also there's a general problem in epidemiologic studies; that is, not seeing the child and looking at records vs seeing the child. All of these issues must be factored into the findings. Eric Fombonne has discussed these issues in some detail.
Medscape: Could the CDC study have overestimated prevalence owing to study design?
Dr. Volkmar: Yes, it's possible. To get the best data, children would have actually been seen and evaluated recently. Or at least a subsample of the children would've been seen to compare results of direct assessment with record review.
Medscape: You mentioned that there are genetic data supporting an actual increase in autism prevalence. Could you elaborate?
Dr. Volkmar: Data suggest that there's a potential for subtle changes in sperm as men get older. To make a long story very short, when women are born they have their full complement of eggs. They're not going to develop any more during their life. Men, on the other hand, are constantly regenerating sperm once spermatogenesis begins. And as men get older, there's an increase in the rate of small mutations. There's some suggestion from studies both here in the United States at the Simmons Foundation and also in Iceland and other locations that older fathers might account for some degree of a true increase in rates of autism.[3,4,5,6]
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Cite this: Two Major Concerns in Autism - Medscape - Jul 10, 2012.