A LARGE-SCALE study of over 2,500 toddlers has found no significant early-age clinical differences between males and females with autism spectrum disorder (ASD), suggesting that sex differences in autistic traits may emerge later in development rather than at the time of first diagnosis.
Understanding whether boys and girls with autism present with different symptoms at the earliest stages of life is crucial for early identification, intervention, and tailoring support. Previous research has produced conflicting results, often limited by small sample sizes and narrow assessment tools. To address these gaps, researchers analysed data from the Get SET Early programme, assessing 2,618 toddlers aged between 12 and 48 months, including those with ASD, developmental delay, and typical development. The study aimed to clarify whether there are meaningful sex differences in autistic traits at the age when symptoms first appear.
The research team used a combination of cross-sectional, longitudinal, and clustering analyses, employing both statistical and machine learning methods. The cohort included approximately 1,500 autistic toddlers, 600 with typical development, and 475 with developmental delay. Assessments covered 19 standardised and experimental measures, including language, motor and cognitive skills, social behaviours, and eye-tracking tests for social attention. Results revealed that, across 17 of 18 measures, there were no significant differences between autistic boys and girls in symptom severity, language, or social attention. The only exception was a slight advantage for autistic girls in daily living skills, as reported by parents. Subtyping analyses, which grouped children by ability rather than sex, also showed no meaningful differences between males and females within the autism spectrum. In contrast, typically developing girls outperformed boys in language, social skills, and daily living abilities.
These findings indicate that at the time of first diagnosis, autistic boys and girls present with nearly identical clinical profiles, challenging assumptions that sex differences are present from the earliest stages. For clinical practice, this suggests that early screening and intervention strategies should not differ by sex, and that focusing on individual strengths and needs, rather than gender, may be more effective. Future research should track autistic children over time to determine when and why sex differences might emerge, and whether social or biological factors play a role. Clinicians are encouraged to use robust, comprehensive assessments and to consider subtypes within autism, rather than sex, when planning interventions and support.
Reference
Nazari S et al. Large-scale examination of early-age sex differences in neurotypical toddlers and those with autism spectrum disorder or other developmental conditions. Nat Hum Behav. 2025;DOI:10.1038/s41562-025-02132-6.
