Autism diagnoses are climbing across the U.S., and a new study suggests that one group has been hiding in plain sight. Researchers at Saint Louis University analyzed electronic health records from 171,134 patients across a large Midwestern health system between 2016 and 2024. Their findings, published in JAMA Network Open, showed that, while new autism diagnoses among boys and men remained stable or even declined, diagnoses among girls and women increased substantially after 2020.
The pattern was seen across every age group studied, including children, adolescents and adults. According to the researchers, the findings suggest that recent increases in autism diagnoses may be driven less by a surge in new cases and more by improved recognition of autism in females. For decades, autism has been diagnosed more frequently in males than females.
Many experts have argued that traditional diagnostic approaches were developed around traits more commonly observed in boys, making it easier for girls and women to go undetected. The new study adds to growing evidence that females on the autism spectrum have historically been underdiagnosed. Girls and women received an autism diagnosis an average of 3.4 years later than boys and men.
The average age at diagnosis was 15.7 years for females, compared with 12.3 years for males. That delay can be significant. Earlier diagnosis often helps children and families access educational support, behavioral therapies and other services that can improve quality of life and help individuals better understand their needs.
Lead author Erick Messias, M.D., Ph.D., chair and professor of Psychiatry and Behavioral Neuroscience at Saint Louis University School of Medicine and a SLUCare physician at SSM Health, said autism is not marked by a single characteristic but by a pattern of behaviours and traits that may look different from one person to another. "For women on the autism spectrum, particularly those who have eluded diagnosis until adulthood, they often engage in significant social camouflaging or masking, which is a conscious effort to conform to social conventions that don’t come naturally to them," Messias told Newsweek. Some autistic people learn to camouflage their differences by mimicking social cues, planning conversations ahead of time and closely regulating their behaviour, Messias said, which can be highly mentally demanding.
While the study did not investigate the reasons behind the delay, the findings suggest many females may be spending years without a formal explanation for challenges they experience. For example, Messias explained that autism in females can sometimes be overlooked because difficulties are more likely to present as internal distress, such as anxiety or depression, rather than disruptive behaviours. "The same diagnostic trend was seen in Attention deficit hyperactivity disorder (ADHD) and led to delayed referral and diagnosis in females as well, so it's not surprising we see a similar pattern across these two conditions," Messias said.
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