Brain Storm

The role of the cerebellum and underlying brain abnormalities in autism.
Brain Storm
Greg Allen

In early October, a study conducted by the Centers for Disease Control and Prevention found that autism rates in the U.S. are much higher than previous estimates. According to CDC statistics, published in the medical journal Pediatrics, approximately 1 in 100 children fall into what’s known as the autism spectrum, up from the previous estimate of 1 in 150.

Autism is the most commonly diagnosed developmental disorder. A higher level of awareness by physicians and the general public, coupled with a much more expansive definition of what behaviors fall into the autism spectrum, are two factors which may be contributing to the increase in diagnoses.

Greg Allen is an associate professor in the Department of Educational Psychology at the University of Texas at Austin. As part of his research, Allen, a licensed psychologist who specializes in neuropsychological assessment, is studying the role of the cerebellum in autism, and how brain abnormalities are linked to the disorder’s behaviors and symptoms. He recently received a three-year $750,000 grant from the National Institutes of Health.

Recent studies suggest that autism rates are much higher than previously thought. What do you attribute this to? Increased awareness? An ever-widening spectrum (Asperger’s syndrome, Rett syndrome, childhood disintegrative disorder, and Pervasive Developmental Disorder Not–Otherwise Specified)? Possible misdiagnosis or overdiagnosis?

I think there are a lot of factors. There’s no question that part of the increase [is due to] our widening definition of the spectrum, as you put it. In 1994 a major event happened in the understanding of autism diagnoses when Asperger’s disorder first appeared in DSM-IV (the Diagnostic and Statistical Manual of Mental Disorders). Before that Asperger’s was a concept in the field of autism but wasn’t widely recognized as a disorder or diagnosis.

In the DSM there are prevalence numbers for various disorders—for autism they were much lower than they are now. For what is technically called autism, the rate was two to five cases per 10,000 individuals, while rates for Asperger’s were not available at the time. So then what happened, the field drifted toward thinking more along the lines of autism spectrum disorders, which include both autism and Asperger’s and to which current prevalence rates typically refer. So, obviously a major widening of what we consider the spectrum to be … contributed to the increased rates. I think it is very important that we try to understand how much of the increase is attributable to a broadening of the spectrum as well as increased awareness in order to understand the potential contribution of other factors that may be of concern.

What is the difference between autism and Asperger’s?

There are a couple of important distinctions between autism and Asperger’s. In autism, you have three main categories of symptoms—impairment in communication, impairment in social interaction, and restricted and repetitive interests and behaviors. What’s different about Asperger’s is that it doesn’t involve a delay in language development. Also, you can’t have any clinically significant delays in cognitive development.


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