The autism diagnosis has become so broad that it prevents a better understanding of how the autistic brain works, a Canadian researcher and psychiatrist says.

In a meta-analysis published in JAMA Psychiatry, researchers in Quebec and Denmark analyzed 11 previous major reviews on people with autism and people in the rest of the population.

Laurent Mottron, a research psychiatrist at the mental health unit of Montreal's Rivière-des-Prairies Hospital and one of the study's authors, said the problem is that the criteria have shifted to the point where a diagnosis could become nearly meaningless.

About 30 years ago, someone would need to show strong differences in social skills, facial expression and other characteristics to receive a diagnosis of autism.

"Now you just have to be slightly diminished," Mottron said. "This paper confirms something everybody at the clinical level knows."

The researchers' analysis found that the differences between the groups in five of the seven main constructs that define autism, including emotion recognition, theory of mind, planning and brain size, have decreased over time.

Blurring the line

Globally, the number of people diagnosed with autism has risen dramatically in recent years. In the U.S., for instance, it has gone from less than 0.5 per cent of the population in 1966 to more than two per cent. In Quebec, the number is approaching two per cent. In 2018, the Public Health Agency of Canada estimated 1 in 66 Canadian children are diagnosed.

It's possible there has been a true increase in the condition, the study's authors say, but there could be other factors that account for their findings, such as greater public awareness and a lowered threshold for diagnosis.

The understanding of autism, they say, has evolved "from a narrowly defined clinical picture to a spectrum of conditions of uncertain similarity." They warn that this blurring of the line could potentially make it more difficult to study.

Mottron said the criteria for a diagnosis have become "trivial," including a child's lack of friends or a dislike of haircuts or tags on clothing.

Dr. Melanie Penner is a developmental pediatrician at Holland Bloorview Kids Rehabilitation Hospital in Toronto. 'I think of the example of a lot of young women who are identifying as autistic now who were missed in earlier years,' she says. (Craig Chivers/CBC)

Currently, parents and teachers and the school system put pressure to obtain an autism diagnosis to get services.

"The problem is an ethical problem," Mottron said. "It's unfair .… because currently being autistic brings more services than being an unidentified condition."

Mottron acknowledged that the situation is complicated because mild forms of autism do exist. However, he noted that having certain autistic traits isn't the same as having autism and said it's "fundamental" for medical professionals to move beyond a simple checklist of symptoms before issuing a diagnosis.

Dermot Cleary, chair of Autism Canada, said Mottron is well respected. Cleary supports the move away from a purely observational-based diagnosis.

"Regardless of what you call a child, the label you put on the child's diagnosis, if they need therapy, they need therapy," Clearly said. "And that's really the main point of it all."

Dr. Melanie Penner — a developmental pediatrician at Holland Bloorview Kids Rehabilitation Hospital in Toronto — says an autism diagnosis is now based on criteria such as poor social skills, difficulties maintaining and developing relationships, restrictive or repetitive behaviours and how those fit in the the current understanding of autism.

"I think of the example of a lot of young women who are identifying as autistic now who were missed in earlier years. They talk about the ways that having an earlier diagnosis would have helped them throughout their life," Penner said. Their experience shows the benefits of greater general awareness.



Marguerite Schabas's son, Peter, 7, has been diagnosed with autism spectrum disorder. The Toronto boy's motor skills allow him to lay wooden train tracks. He's nonverbal.



"If you need glasses you should be able to get them. It doesn't matter what intensity your prescription is, but you need the right prescription. For our kids, it's the same thing. They have different needs."



She said with support, Peter's now thriving.