Being diagnosed with autism could be a lot more difficult if a new diagnostic definition goes into effect.

In its next manual on mental disorders, the American Psychiatric Association plans to issue a single set of diagnostic criteria that will merge the four types of disorders on the autism spectrum, which include autism and Asperger syndrome. Although no current patient will be affected by the new rules, research by Yale Child Study Center Director Fred Volkmar suggests that the revision may disqualify a large number of intellectually disabled patients from receiving a diagnosis of autism spectrum disorder in the future. Though the study is still embargoed, with at least a month before publication, Volkmar presented his data Jan. 19 to the Icelandic Medical Association, creating widespread alarm about the new criteria.

“I think [the proposed revision] is a mistake,” Volkmar said. “It changes people’s eligibility for key services, and a lot of people expressed concern.”

He said the change would not only affect autistic patients’ access to medication and medical services, but also impact their eligibility for special schools. Volkmar also questioned the scientific validity of the decision.

In their study, Volkmar and his team looked at a group of individuals with moderate cognitive disabilities who had been evaluated in 1994, when the APA was formulating its previous autism definition. Over half of those patients who were diagnosed with some form of autism spectrum disorder would no longer receive that diagnosis if they were evaluated under the new definition, Volkmar said.

Volkmar said the revision may have been motivated by an attempt to be “economical” at the cost of denying services to some patients with less severe symptoms.

Meanwhile, the APA said in a press release that the recommendations “reflect the work of dozens of the nation’s top scientific and research minds,” and insisted that merging the disorders will result in more sound diagnoses. The press released also disputed the fact that any type of person who was previously classified as autistic would not receive an equivalent diagnosis under the new guidelines.

“Distinctions among disorders have been found to be inconsistent over time [and] variable across sites,” the APA wrote. “Previously, the criteria were equivalent to trying to ‘cleave meatloaf at the joints.’”

Members of the APA’s autism panel could not be reached for comment.

The changes have also sparked concerns from students, including Jacqueline Lee ’14 and Salma Dali ’14, members of Best Buddies, a nonprofit that pairs students with intellectually disabled individuals to create friendships .

“It’s still important to recognize and diagnose [less severe cases] so that they can receive proper care and attention,” Dali said. “Without a diagnosis and subsequent support, people may not be able to achieve the same levels of success.”

Lee said if the change denies services to high-functioning individuals, they may still be able to survive without assistance, but will be unable to reach their full potential. She said she worries that denying them support may prevent them from overcoming societal stigma against their handicap and integrating themselves into society.

Autism researcher Nicholas Lange, a psychiatry and biostatistics professor at the Harvard Schools of Medicine and Public Health, said it is possible that some patients would be excluded under the new criteria, adding that while he believes that both Volkmar’s and the APA autism panel’s data on the new diagnosis criteria are sound, their selection of different sample groups of patients makes the question of significant patient exclusion “not entirely determinable.”

“I would favor the overwhelming evidence of the data which, apart from its effect on insurance companies, shows that Asperger and [other spectrum disorders] are indistinguishable from autism at present,” said Lange.

While Volkmar continues to hope for a reversal, he said it is difficult to know if the changes will be reconsidered, adding that “the whole process has not been terribly comforting.”

Volkmar’s complete study will be published in the April print edition of the Journal of the American Academy of Child and Adolescent Psychiatry.

Correction Feb. 2

An earlier version of this article misquoted Harvard professor Nicholas Lange as saying that insurance companies “would no longer be able to discriminate against [high-function individuals with autism] relative to more [severely affected] patients.” In fact, Lange said when third-party payers see an opportunity to deny coverage to more severely affected individuals in any disabled population, they will likely take it.