For decades, autism has been treated as a condition that mostly affects boys. New research suggests that idea is falling apart, and fast, at least when it comes to how many women and girls are now getting diagnosed.

A study published in JAMA Network Open followed more than 171,000 patients in a multistate health system from 2016 to 2024. It found that new autism diagnoses among males held steady or even dropped during that time. Diagnoses among females, though, jumped sharply after 2020, climbing by 19% a year between 2020 and 2024. Women and girls were also diagnosed an average of 3.4 years later than men and boys, a delay that could mean additional years without the accommodations and support that come with an official diagnosis.

What’s happening here goes beyond a simple rise in autism cases. It points to groups that have been overlooked for years. Researchers say the pattern may help explain part of the broader rise in autism diagnoses: doctors are increasingly recognizing people who were historically missed, particularly women and girls, who often display the condition differently than men and have long slipped past screening tools designed around male behavior.

Researchers pulled medical records from a health system spanning Illinois, Missouri, Oklahoma and Wisconsin, covering both rural and city communities. They focused on patients who visited a doctor at least once a year, every year, from 2016 through 2024. That requirement was meant to capture people who stayed consistently connected to the health care system rather than those who only showed up occasionally.

That left a group of 171,134 people, split into three age brackets: children ages 0 to 9, teens ages 10 to 18, and adults ages 19 to 50. Nearly 64% of the group was female, likely because women tend to see doctors more often than men, especially during their reproductive years.

Researchers tracked new autism diagnoses recorded in medical records, then used a statistical method to pinpoint the exact years when diagnosis trends shifted direction, similar to spotting the moment a rising or falling line on a graph suddenly bends.

That pattern held up across every age group. Among children, boys saw a small, steady decline in new diagnoses, while girls saw a sharp rise starting in 2020. Among teens, boys’ diagnosis rates dropped early on and then flattened out, while girls’ diagnoses spiked between 2020 and 2024. Among adults, men’s rates trended down while women’s rates trended up, though that adult female trend wasn’t strong enough statistically to rule out chance.

A gap in timing showed up early, too. Boys were typically diagnosed around age 12 and girls around age 16, a difference of about three and a half years. Among young children alone, girls were typically diagnosed around age eight and a half, compared with about seven for boys, meaning a delay of more than a year already exists during the elementary school years, when developmental screening is typically most active.

Researchers also tracked the disappearance of “Asperger’s syndrome,” a diagnosis that was folded into the broader autism spectrum category back in 2013 under updated psychiatric guidelines. Even though the old medical code for Asperger’s stayed in use in some systems, doctors mostly stopped using it in favor of the broader autism label, and new diagnoses under the old code steadily vanished across every age group during the study.

To rule out pandemic disruptions to routine care, researchers tested what would happen if they removed 2020 data entirely. The core pattern didn’t change. Female diagnoses kept climbing, and male diagnoses stayed flat or fell, suggesting the pandemic alone doesn’t explain what’s happening.

Researchers point to earlier work showing that women and girls with autism often behave differently than men and boys with the condition. Females are more likely to mask or hide their traits, appearing more socially at ease on the surface in ways that can fool screening tools built mainly around how autism looks in boys. That means many girls may meet the criteria for autism for years before anyone notices, especially if they’re managing well enough to avoid raising concern during early childhood checkups.

By the time social pressures ramp up in middle school and high school, some of these girls start struggling to keep up the appearance of fitting in, which may explain why teenage girls saw such a steep jump in new diagnoses between 2020 and 2024. The paper also raises another possibility: growing awareness and conversation online may be helping adult women recognize traits in themselves that were never caught earlier in life, prompting them to seek an evaluation later than they otherwise might have.

None of this proves autism itself has suddenly become more common. One explanation the researchers raise is that screening tools have historically been better at catching the ways autism commonly appears in boys, making some girls easier to miss. As those blind spots get recognized, more women and girls are being identified.

For doctors, schools and families, the study carries a clear message: the old assumption that autism is mostly a male condition has shaped who gets screened, who gets flagged, and who gets left behind. A 3.4-year average delay in diagnosis for females isn’t a small statistic. It could translate into years of delayed access to diagnosis-linked accommodations, community connection, and the kind of early understanding that can shape how a person grows and copes. Unless screening tools and clinical training start catching female presentations earlier, that gap isn’t likely to close on its own.

For families who have watched a daughter or sister struggle for years without answers, the findings may offer some validation: girls and women really have been an underrecognized part of the autism population.

Disclaimer: This article summarizes peer-reviewed research and is intended for general information only, not as medical advice. Autism spectrum disorder is diagnosed by qualified clinicians through comprehensive evaluation. Anyone with questions about autism or a possible diagnosis for themselves or a family member should consult a licensed medical or mental-health professional. The findings described here reflect first recorded diagnoses within a single US health system and may not apply to every population or setting.