A debate among medical professionals over how to define autism has spilled over into the public domain, stirring anger and fear among many parents and advocates of those with the neurological disorder, even as some argue that the diagnosis has been too loosely applied.
A study reported on Thursday found that proposed revisions to the American Psychiatric Association's definition would exclude about three-quarters of those now diagnosed with milder forms of autism called Asperger syndrome or "pervasive developmental disorder, not otherwise specified," also known as P.D.D.-N.O.S. These are people who have difficulties with social interaction but do not share the most severe impairments of children with classic autism.
"He was right on the border, they told me when he got the diagnosis; that's what scares me," said Amanda Forman of Flourtown, Pa., whose 5-year-old son was diagnosed two years ago with P.D.D.-N.O.S. After receiving play therapy, occupational therapy and 17 hours a week of behavioral therapy, the boy, who was once unresponsive to other children and engaged in self-destructive behavior, may enter a mainstream kindergarten class next year, his mother said. "What if he has to be re-evaluated? If the criteria were stricter, he might not get these services that have been helping him so much."
The proposed revisions, which would take effect in 2013, are likely to have practical implications for those who would once have qualified for services that experts say can improve an individual's abilities to socialize, learn and ultimately live independently. But they have also ignited a broad discussion over the value of a diagnosis for behavior differences, and how to fairly apportion services at a time when resources are shrinking.
The Diagnostic and Statistical Manual, now under revision, is the standard reference for mental disorders, driving research, treatment and insurance decisions. Since 1994, when recognition of Asperger syndrome was first included as an autism-spectrum disorder, diagnosis of the condition has surged.
Over the last decade, the number of 6- to 21-year-olds with autism in public schools has quadrupled, according to the Department of Education. Such students may get private school placement, a classroom aide or curriculum adaptations. In recent years, 29 states have passed laws requiring insurance companies to provide behavioral therapies and other forms of care to people with an autism diagnosis.
"We have to make sure not everybody who is a little odd gets a diagnosis of autism or Asperger disorder," said Dr. David J. Kupfer, a professor of psychiatry at the University of Pittsburgh and chairman of the task force making the revisions, which are still subject to change. "It involves a use of treatment resources. It becomes a cost issue."
But some autism advocates argue that acknowledging the neurological basis for socially odd behaviors has benefits beyond eligibility for services, promoting cultural tolerance and a degree of self-understanding that may be lost without it.
"Having a diagnosis helps people understand why we process thoughts and emotions differently and make positive changes," said Michael John Carley, director of the Global and Regional Asperger Syndrome Partnership, which urged members to call the psychiatric association to complain. "Sadly, we may be heading back to the days when our differences are seen through the lens of character deficits rather than in the context of brain wiring."
Even within the medical community, the number of people who would not be eligible for an autism diagnosis under the new criteria is a matter of dispute. Some may fall under a new category, "social and communication disorder," though it is not clear what kind of aid, if any, they would be eligible for as a result.
Catherine Lord, the director of the Institute for Brain Development at NewYork-Presbyterian Hospital, and a member of the committee overseeing the revisions, said that the goal was to ensure that autism was not used as a "fallback diagnosis" for children whose primary trait might be, for instance, an intellectual disability or aggression.
She said the committee's own data shows that very few who currently have a diagnosis would be dropped. And another analysis of the effect of the proposed new definition, published this month in The Journal of the American Academy of Child and Adolescent Psychiatry, found that roughly 40 percent of individuals with Asperger syndrome would not be given a diagnosis under the new definition. That study suggested that altering the criteria slightly could recapture most of those who would otherwise be excluded.
Yet some parents of severely autistic children who are nonverbal, and may need constant care to avoid injuring themselves and others, say they would welcome a narrowing of the spectrum.
"Everyone on the spectrum benefits when money and services available are applied more specifically and appropriately to the individual needs of each person affected," said Mark L. Olson, of Henderson, Nev., whose daughter, 16, does not speak. Mr. Olson has argued on his blog that those with more severe needs have been overshadowed by people with the Asperger diagnosis, who have typical intelligence and language development.
Many comments, on the Web site of The New York Times and elsewhere, expressed the view that autism was overdiagnosed: "Come on, 1 in 100 children today?" one commenter wrote. "This pathology did not exist in the past because we did not label it."
And even some parents of autistic children noted in the debate this week that a diagnosis can be a double-edged sword.
"With it, a child gets needed services," wrote one Boston parent, whose son has a language impairment that makes socializing difficult. "The downside is that a child will be perceived by his peers as being abnormal and shunned socially. I noticed a huge change after my son was diagnosed. Once he got the autism label he rarely got birthday party invitations, for instance."
But like many parents, Ms. Forman, who requested that her maiden name be used to shield her son, said she sought the diagnosis only because her son so badly needed the services it would secure.
"I didn't know that feeling was so prevalent, that autism is so overdiagnosed," she said, having read many of the comments on Web sites. "I just know the amount of work I do for him, and that's not something I would do if I didn't have to do it.
"It's not the easy way out for anybody."