Autism Diagnosis Rates Approaching Parity Between Males and Females, New Study Suggests
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A new study published in The BMJ indicates that the historically skewed ratio of autism diagnoses – traditionally three boys for every one girl – is shifting, with rates among females rapidly increasing, particularly in adolescence and adulthood. This suggests that autism has been significantly underdiagnosed in girls and women for years, and diagnostic practices are beginning to reflect a more accurate prevalence.
The Shifting Landscape of Autism Diagnosis
For decades, autism spectrum disorder (ASD) was considered a predominantly male condition. However, growing evidence suggests this perception was largely due to diagnostic biases and a lack of understanding of how autism presents differently in females. The new research, a population-based study tracking autism incidence in Sweden, reveals a consistent 3:1 male-to-female ratio for children diagnosed before age 10. However, this ratio dramatically changes with age, declining rapidly after 10 and approaching parity – a 1:1 ratio – by age 20.
“The headline ‘Rates of autism in girls and boys may be more equal than previously thought’ is seriously misleading,” cautioned Prof Dame Uta Frith, Emeritus Professor of Cognitive Development at University College London (UCL). “The study shows the sex ratio has remained steady for children diagnosed below age 10, but declines rapidly after that, suggesting a significant number of females are being diagnosed later in life.”
Why the Delay in Diagnosis for Females?
Experts attribute the delayed diagnosis in females to a variety of factors, including societal expectations, masking behaviors, and clinical biases. Masking, a phenomenon where autistic individuals consciously or unconsciously suppress their autistic traits to fit in, is thought to be more prevalent in girls and women. This can make it harder to identify autism, as their presentations may be less stereotypical.
“Autistic women and girls have often been missed because of subtler behaviours from trends toward more imitation and masking, including more eye contact than male counterparts,” explained Dr. Steven Kapp, Senior Lecturer in Psychology at the University of Portsmouth. “Research has revealed that clinical biases contribute to under-recognition of women and girls, which we in the autistic community have long critiqued.”
Dr. Rachel Moseley, Principal Academic in Psychology at Bournemouth University, emphasized the importance of longitudinal studies. “This paper provides important support for what autism researchers have known for a long time: that autism is markedly undiagnosed in people assigned female at birth,” she stated. “The signs of autism are often only visible at a slightly later age in girls; studies looking only at toddlers may miss autistic features already present in males but not yet visible in females.”
Implications for Healthcare and Well-being
The increasing recognition of autism in females has significant implications for healthcare and well-being. Underdiagnosis can lead to years of misdiagnosis, inappropriate treatment, and increased rates of co-occurring mental health conditions like anxiety, depression, and eating disorders.
Dr. Laura Hull, Research Fellow at the University of Bristol Medical School, noted the importance of considering the “whole picture” of individuals being assessed, given the high rates of these co-occurring conditions. “Accounting for the whole picture of individuals being assessed is important considering the high rates of conditions such as anxiety, depression, and eating disorders in this group,” she said.
Furthermore, research indicates that being undiagnosed can have severe consequences. “What we know about undiagnosed autistic people is that being undiagnosed is often associated with severe difficulties and even suicidality,” Dr. Moseley added, highlighting the urgent need for improved diagnostic practices.
A Global Issue, Not Just a Swedish Trend
While the study focused on data from Sweden, experts believe the trend is not isolated. Dr. Monique Botha, Associate Professor in Social and Developmental Psychology at Durham University, pointed out that similar patterns are observed in the UK. “Importantly, these diagnostic disparities are not unique to Sweden,” she said. “We see parallel patterns in the UK and given the UK’s more fragmented diagnostic pathways and constrained infrastructure, there is good reason to think these inequities may be even more pronounced here.”
The study’s findings underscore the need for increased awareness, improved diagnostic tools, and a more nuanced understanding of how autism presents in individuals of all genders. As diagnostic rates continue to evolve, it remains to be seen whether the male-to-female ratio will continue to decrease, stabilize, or potentially even increase again as healthcare systems “catch up” with the diagnosis of previously missed cases.
The research, ‘Time trends in the male to female ratio for autism incidence: population based, prospectively collected, birth cohort study’ by Caroline Fyfe et al., was published in The BMJ at 23:30 UK time on Wednesday, February 4, 2026. The study’s DOI is 10.1136/bmj-2025-084164.
