Male toddlers with autism have significant structural differences in their brains compared to females with the condition, according to research published in the open access journal Molecular Autism. The journal is publishing a special series of articles looking at the links between sex/gender and autism, which reveal additional insights into the role of prenatal sex hormones and the 'female protective effect'.

Autism spectrum conditions are more common in males than in females, with a 2 or 3:1 male to female bias in prevalence consistently found in studies. Why this is the case is still not fully understood.

Guest editor Meng-Chuan Lai from the Autism Research Centre, University of Cambridge, UK, said: "Autism has always been perceived as a condition that occurs more often in males, which means that females are usually underrepresented in research studies. This means there's a risk that the scientific and clinical literature provides a partial, male-based understanding of autism.

"But autism is clearly not a 'male condition'. Delineating the role that sex and gender play in the characteristics of autism, across multiple levels, may inform both our ability to identify the condition and lead to a greater understanding of its developmental psychology and biology."