Autism advocates are worrying that proposed changes to the way that autism is defined could affect the way that children and adults with the condition access treatment and services.

An expert panel appointed by the American Psychiatric Association is considering narrowing the definition of autism as it completes its fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, or DSM V, as it's known.

The DSM is the standard reference book for mental health disorders and hasn't been revised in 17 years. Most expect the new edition will narrow the criteria for autism to make it more stringent.

But there is debate about how much the change will affect those with autism.

The new definition is expected to emphasize "classical autistic," or the more severe symptoms.

Under the current criteria a person can qualify for the diagnosis by exhibiting six or more of 12 behaviors. Under the proposed definition, the person would have to exhibit three deficits in social interaction and communication, and at least two repetitive behaviors.

The proposed change would bring all three diagnoses under one term: autism spectrum disorder. That means that the terms Asperger's syndrome and P.D.D.-N.O.S. (pervasive developmental disorder, not otherwise specified) would be eliminated.

The idea behind the change is that it would slow the trend of rising diagnoses.

Support services at risk

The rates of autism have surged since the 1980s, with some figures suggesting as many as one in 110 children have the disorder. Some contend that many kids with other communication and developmental problems are being unfairly lumped into autism, when they don't meet the classic definition.

But The New York Times reports that a new analysis presented Thursday at a meeting of the Icelandic Medical Association found that the changes could mean that many people currently described to have the condition would no longer meet the criteria. And that might mean they would no longer be able to access certain health, educational and social services.

But Catherine Lord, a member of the task force working on the diagnosis, disputes the analysis and tells the Times that very few people would be excluded under the change.

Leah Miltchin, the head of the board of directors at Autism Ontario, says the worry among the autism community is that if some people are excluded from the autism definition, they might no longer be able to access certain health, educational and social services.

"That is the concern that a lot of parents currently have. If you have a child with a diagnosis of Asperger's syndrome and they qualify for certain supports, when the diagnostic criteria change, they may not fit under the ASD umbrella anymore," she tells CTV News.

And yet a person with Asperger's syndrome would still need support services, she notes.

"Even if the diagnostic criteria change, the needs that are there will still be there," she says.

But Dr. Wendy Roberts of the autism unit at the Hospital for Sick Children in Toronto says a more narrow definition could be good in the long run for treatment of the disease.

"Reworking the diagnosis will help clinicians, physicians and psychologists ... to be more specific about the areas of impairment they need to look at," she says.

"Having that spelled out is a good thing to do."

Roberts cites two studies that found few people would be excluded under the new definition of autism.

The revisions, now under review by a group of experts, are said to be about 90 per cent complete and due to be finalized by the end of the year.

Christina Buczek, whose 15-year-old daughter Emily has autism, says she agrees that the current definition has become pretty wide.

"I would say that with the current diagnosis of the spectrum, the umbrella term has become so wide that it's in a way meaningless," she told CTV News Channel Friday.

She says someone who is high functioning but has some communication problems is a long way from someone like her daughter, who doesn't speak at all.

"If you were to take my daughter and put her beside someone at the other end of the spectrum -- who would be maybe somebody with Asperger's – there would be very remote similarity between the two."

The changes would most affect people in some U.S. states where having Asperger syndrome or the broad diagnosis of a "pervasive development disorder" means they don't qualify for services. The changes would spell good news for some of these people who might be redefined as having autism disorder.

But others who do have Asperger's syndrome don't like the idea that they might be redefined as having autism disorder, which they worry carries more of a stigma than the term Asperger's.

With a report from CTV's medical specialist Avis Favaro and producer Elizabeth St. Philip