Sex differences in autism spectrum disorder: evidence from a large sample of children and adolescents.

Mandy et al. (2012) looked at boys and girls with autism side by side. They tracked kids aged 3 to 18 who had high-functioning ASD. The team compared repetitive behaviors and teacher reports of school problems between the sexes.

Girls showed milder repetitive behaviors than boys at every age. Teachers also reported fewer classroom problems for girls. These steady sex differences hint at a girl-friendly version of autism that can hide in plain sight.

Bassett-Gunter et al. (2017) seems to disagree. In their large sample they found boys and girls with ASD scored almost the same on symptom tests. The gap is tiny and likely not meaningful in daily work.

The papers differ because they sampled different worlds. William’s group came mainly from school lists, where milder girls are already noticed. L et al. pulled from all clinics and ages, washing out the school effect.

Hodge et al. (2025) later matched William’s story. Girls in their Sydney clinic were assessed six months later than boys, backing the idea that milder traits delay detection.

If you rely only on standard severity cut-offs, girls can slip past. Add sex-specific questions to your intake: ask about subtle routines, social mimicry, and teacher comments. When a girl shows even mild restricted interests, probe further instead of waiting for bigger red flags.