Autistic girls four times less likely to get childhood diagnosis than boys, study finds

Boys were three to four times more likely than girls to be diagnosed with autism under the age of 10. File picture

Females may be just as likely to be autistic as males but boys are up to four times more likely to be diagnosed in childhood, according to a large-scale study.

Research led by the Karolinska Institutet in Sweden scrutinised the diagnosis rates of autism for people born in Sweden between 1985 and 2020. Of the 2.7 million people tracked, 2.8% were diagnosed with autism between the ages of two and 37.

They found by the age of 20, diagnosis rates of men and women were almost equal, challenging previous assumptions autism is more common among males.

“Our findings suggest the gender difference in autism prevalence is much lower than previously thought, due to women and girls being underdiagnosed or diagnosed late,” said the lead author, Dr Caroline Fyfe.

The research calculated that in childhood, boys were diagnosed on average nearly three years earlier than girls — the median age at diagnosis was 15.9 for girls, but 13.1 for boys. 

Overall, boys were three to four times more likely than girls to be diagnosed with autism under the age of 10, although girls were found to “catch up” by the time they were 20, owing to a rapid increase in autism diagnosis during adolescence.

The study, published in the British Medical Journal, also found while gender disparities in diagnosis rates remained pretty consistent over the last three decades for children under 10, they decreased rapidly for all other age groups.

“Findings indicate that the male to female ratio for autism spectrum disorder has decreased over time and with increasing age at diagnosis,” the authors observe.

“This male to female ratio may therefore be substantially lower than previously thought, to the extent that, in Sweden, it may no longer be distinguishable by adulthood.”

Patient advocate Anne Cary, writing in a linked editorial, said the research supported arguments it was “systemic biases in diagnosis, rather than a true gap in incidence” that were behind the discrepancy in diagnosis rates.

While the onset of symptoms could be delayed and masking was undoubtedly a factor, the methods and tools to diagnose autism might be biased and need refining, she said. “These biases have meant that a girl who would ultimately have a diagnosis of autism would have a less than third of a chance of receiving a diagnosis before the age of 10 years.

“As autistic girls and women await proper diagnosis, they are likely to be [mis]diagnosed with psychiatric conditions, especially mood and personality disorders, and they are forced to self-advocate to be seen and treated appropriately: as autistic patients, just as autistic as their male counterparts.” 

The Guardian