Women Catch Up to Men in Autism Diagnoses by Age 20

Millions of autistic girls may be slipping through the cracks in childhood, only to finally get diagnosed as adults, according to powerful new research from Sweden.

Scientists followed 2.7 million children born between 1985 and 2020, creating one of the largest autism studies ever conducted. What they found challenges everything we thought we knew about who gets diagnosed.

In early childhood, boys were much more likely to receive an autism diagnosis. But as these children grew up, something remarkable happened: a "catch-up" effect emerged. By age 20, women were almost equally as likely to have been diagnosed with autism as men.

This flips the old assumption on its head. The U.S. Centers for Disease Control and Prevention currently reports that boys are three times more likely to be diagnosed as autistic than girls. For years, scientists wondered if male brains were simply more prone to autism, or if genetics held the answer.

The truth appears far simpler and more troubling. Girls are being missed.

The Ripple Effect

When autism goes undiagnosed in childhood, the consequences ripple through a person's entire life. Girls may be masking their symptoms out of instinct or necessity, working twice as hard to appear "normal" while struggling inside.

Without proper diagnosis, these girls often get mislabeled with anxiety or ADHD instead. They miss out on the right treatments and support systems that could make their lives easier. They spend years wondering why they feel different, without understanding why.

David Mandell, a psychiatry professor at the University of Pennsylvania, called the study "interesting" and "well done," praising its 35-year timespan and massive dataset. Gina Rippon, an expert on cognitive neuroimaging and author of "The Lost Girls of Autism," went further, calling the results "powerful" and "sound."

Rippon noted that because the study relied on clinical diagnoses, it might actually underestimate how many women are autistic. The real numbers could be even higher.

The study points to systemic biases in how doctors diagnose autism. The diagnostic tools and checklists may have been built around how autism looks in boys, missing the different ways it can show up in girls.

Anne Cary, a patient advocate, wrote that this delayed recognition has real costs. Autistic people work harder to get proper treatment and often face years of confusion and misdiagnosis.

Rippon sees hope in this discovery. "If this study does nothing other than indicate what is going on in the recognition of autistic women, then that will be great," she said.

This research, published in the BMJ medical journal, gives doctors and parents a wake-up call: if a girl seems to be struggling, autism deserves serious consideration, not dismissal. Understanding this gap is the first step toward closing it and ensuring every child gets the support they deserve from the start.