FRIDAY, Jan. 20, 2012 (HealthDay News) -- The number of people diagnosed with autism will likely decrease if a new definition of the disorder is adopted by mental health experts later this year.
Doctors aren't sure what the implications of the changes will be, but they agree there will be an impact on the lives of people with autism and the professionals who treat them. The changes could affect the number of people eligible for health, educational and social services.
But some experts contend that a clearer definition of autism is needed because the current definition is too hazy and may have contributed to an exaggerated number of people with the developmental disorder.
"This is not an academic exercise," said Geraldine Dawson, the chief science officer for Autism Speaks, an advocacy organization, and a professor of psychiatry at the University of North Carolina at Chapel Hill. "These changes in the diagnostic criteria will have a real impact on people's lives and we have to be very careful as we begin to implement the new criteria that we monitor how this is affecting people's ability to obtain services."
The new definition would create just one diagnostic category -- autism spectrum disorder -- that would replace the three subtypes that are used now. Those subtypes are Asperger syndrome, autism spectrum disorder and pervasive developmental disorder-not otherwise specified (PDD-NOS).
The revised definition of autism is being drafted by a panel of experts appointed by the American Psychiatric Association. The new definition will be part of the psychiatric association's Diagnostic and Statistical Manual of Mental Disorders (DSM), the "bible" for psychiatric diagnoses. The manual is currently in its fourth edition, which was released in 1994, but the much-anticipated fifth edition should be final by the end of this year.
Although the new definition of autism isn't final, it's "very likely," Dawson said. "They [the expert panel] are extremely close, so any changes at this point will probably be relatively minor."
Estimated rates of autism in the United States have surged since the 1980s, with some recent figures running as high as one in every 110 children. Some experts say there has been a bona fide increase in the number of cases, while others contend that the lack of clear-cut diagnostic guidelines is to blame.
Autism is a complex neurodevelopment disorder with typical symptoms that include difficulty communicating with others, the inability to form social relationships, and repetitive movements such as rocking and twirling, or even self-abusive behavior such as biting or head-banging, according to the U.S. National Institute of Neurological Disorders and Stroke.
The cause of autism remains unknown.
Under the new definition of autism, Asperger syndrome, which generally describes a higher functioning individual, would be eliminated, as would PDD-NOS, a sort of catch-all category.
A study presented Thursday at a meeting of the Icelandic Medical Association estimated that less than half (45 percent) of 372 children and adults diagnosed with autism in a 1993 paper would qualify under the new criteria, The New York Times reported.
A previous study came to a similar conclusion, Dawson said, with both papers appearing to identify fewer people with autism.
"In particular, they're identifying fewer individuals who are higher functioning, for example, Asperger [syndrome patients]," she said.
From a scientific point of view, the changes in diagnostic criteria make sense, Dawson said. The subcategories don't have any meaning in terms of etiology, or what causes autism. Nor do they necessarily differentiate recommended treatments, she added.
And clinicians don't always agree on diagnoses for particular individuals.
But science aside, Dawson said, "We have to keep in mind the real-world implications. In particular, we have to be very careful that through this process that we're not excluding people from receiving services that they need and deserve."
Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at the Steven and Alexandra Cohen Children's Medical Center of New York in New Hyde Park, said the new definition is "trying to lend some greater precision" to the diagnosis of autism.
But, so far, experts aren't even sure if the recent estimates of autism's prevalence are correct, he said. "There are differences of opinion," he added.
"Only time will tell what kind of impact this will have," Adesman said.
The U.S. National Institute of Neurological Disorders and Stroke has more on autism.