New study challenges old hypothesis about autism diagnosis

New study challenges old hypothesis about autism diagnosis

Boys are more likely to be diagnosed with autism than children, but as adults this trend changes, according to a new Swedish study.

By Jackie Flynn Mogensen edited by Claire Cameron

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According to the U.S. Centers for Disease Control and Prevention, boys are approximately three times more likely to be diagnosed with autism than girls. Scientists have sought an answer to why this imbalance exists: some have argued that it is due to male and female brains; others have proposed that genetic differences or another biological factor might hold an answer. And there is evidence that some girls and women misdiagnosed– or completely missed.

But one new study involving millions of people in Sweden, shows that women and men are almost equally likely to be diagnosed with autism as adults, suggesting that young girls may be underdiagnosed and possibly not benefit from intensive care.

Scientists tracked 2.7 million children born in Sweden between 1985 and 2020, of whom around 2.8% had been diagnosed with autism by 2022. In early childhood, boys were much more likely to be diagnosed with autism. But as the cohort aged, the researchers identified a “catch-up” effect: by age 20, women were almost as likely as men to have been diagnosed with autism. The research was published in the BMJ.

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The study is “interesting” and “well done,” says David Mandell, a professor of psychiatry at the University of Pennsylvania, who points to the study’s 35-year time frame and large data set.

Gina Rippon, Emeritus Professor of Cognitive Neuroimaging at Aston University in England and author of the book The Lost Daughters of Autismagrees. The results are “powerful” and “robust,” says Rippon. “This is a very rigid study, perhaps classic Scandinavian type, where the data is amazing data, collected over time, valid, reliable, etc.”

Indeed, because the study relies on clinical diagnoses, its results may actually be a “conservative” estimate of autism rates in women, she adds.

It is unclear what might explain the early diagnosis gap between boys and girls. One possibility lies in “systemic biases in diagnosis,” Anne Cary, a patient and patient advocate, wrote in a statement. related BMJ editorial. In other words, the way clinicians diagnose autism may be neglecting girls. Girls, “by instinct or by necessity,” can also mask this disease.

And this has real consequences. Late diagnoses can mean autistic people have to work harder to get the right treatment and may be misdiagnosed with conditions like anxiety or ADHD in the meantime.

Rippon says the new study could be a step toward correcting that legacy. “If this study does nothing other than indicate what is happening in the recognition of autistic women, then that will be great,” she says.