Autism diagnoses may occur later in girls than in boys

A large Swedish study of about 2.7 million people found boys are more likely to receive autism diagnoses in childhood while girls’ diagnosis rates rise in adolescence, with no significant sex difference by age 20.

Researchers report that autism diagnoses often occur earlier in boys than in girls, but diagnosis rates between sexes level out by around age 20. The finding comes from a study led by Karolinska Institutet and published in The BMJ that followed roughly 2.7 million people born in Sweden between 1985 and 2022 over about 35 years. During that period researchers recorded tens of thousands of diagnosed cases with peak diagnosis ages differing by sex. The authors said the pattern points to many females being diagnosed later rather than autism being inherently more common in males. Key findings: - The study followed about 2.7 million people born in Sweden from 1985–2022 and tracked diagnoses over several decades. - Around 78,522 autism diagnoses were recorded; boys were most often diagnosed at ages 10–14 and girls at 15–19. - By age 20, diagnostic rates between males and females showed no significant difference, described by the authors as a substantial catch-up effect. - Researchers suggested several explanations, including a possible female protective effect, girls masking autistic traits in social settings, and diagnostic criteria that may favour male presentations. Summary: The study indicates many girls may be diagnosed later than boys, producing a narrowing of sex differences in diagnosis by early adulthood. Authors call for further investigation into why female individuals receive diagnoses later; specific next steps are undetermined at this time.