A recent study from Sweden, published in The BMJ, challenges the traditional belief that autism spectrum disorder (ASD) is much more common among males than females. Researchers analyzed national data for 2.7 million individuals born between 1985 and 2022, tracking diagnoses from birth up to age 37.
The findings reveal that while boys are more likely to be diagnosed with autism during childhood, girls catch up in adolescence. Diagnosis rates peaked at ages 10-14 for males and 15-19 for females. By age 20, the male-to-female diagnosis ratio approached parity.
During the follow-up period of over 35 years, autism was diagnosed in 78,522 individuals—about 2.8% of the cohort—at an average age of 14.3 years.
"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," the authors wrote.
They also highlighted: "These observations highlight the need to investigate why female individuals receive diagnoses later than male individuals."
The study is observational and did not account for co-occurring conditions like ADHD or intellectual disability, nor could it control for factors such as parental mental health. Still, its large size and extended duration allowed researchers to assess changes across age groups and generations.
Anne Cary, a patient and advocate writing in a linked editorial, commented on these results: "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." She emphasized that studies like this help challenge long-standing assumptions about gender differences in autism prevalence.
