A Swedish nationwide registry study following more than 2.7 million people born between 1985 and 2020 found that autism spectrum disorder diagnoses occur earlier and more frequently in boys during childhood, whereas girls are often identified later, with the male-to-female diagnosis ratio narrowing substantially by age 20. These findings suggest that historical sex differences in autism spectrum disorder prevalence may reflect diagnostic practices and underrecognition in females rather than true differences in incidence.

Source: The BMJ study and editorial