It is debated whether this is due to a sex difference in rates of autism spectrum disorders (ASD) or whether females are underdiagnosed.
Another early researcher, Leo Kanner described "autistic disturbances of affective contact" in the group consisting of eight boys and three girls.
Individuals with ASD were found to have widespread abnormalities in interconnectivity and general functioning in specific brain regions.
[16] Although autistic females have been documented to have higher testosterone levels, which could support the extreme male brain theory, not all autistic females show male-specific symptoms, leaving the extreme male brain theory with Autism Spectrum Disorder to be controversial.
[17][18][19] According to the female protective effect hypothesis, more genetic mutations are required for a girl to develop autism than for a boy.
In 2012, Harvard researchers published findings suggesting that, on average, more genetic and environmental risk factors are required for girls to develop autism, compared to boys.
The researchers analyzed DNA samples of nearly 800 families affected by autism and nearly 16,000 individuals with a variety of neurodevelopmental disorders.
[20] Women with an extra X chromosome, 47,XXX or triple X syndrome, have autism-like social impairments in 32% of cases.
[28] Recent literature has exemplified that autistic females present lower levels of restricted and repetitive interests.
[29] Masking is the act of constantly monitoring one's behavior in order to hide one's autistic traits and/or putting on a fake persona.
Examples of this can include mimicking real or fictional people, over exaggerating non-verbal expressions, and creating scripts or rules when having a conversation with someone.
[34] Many theories exist regarding the suggested link between gender diversity and autism: Vanderlaan et al.[36] proposed that a high birth weight could be the determinant of this co-occurrence, but this idea is challenged by its association with lower fetal testosterone, contradicting other autism theories such as Baron-Cohen's Extreme Male Brain hypothesis.
Psychologically, early theories from Landén et al. (1997) and Williams (1996) linked transidentity in autistic individuals to restricted interests or obsessive preoccupations, though these ideas have largely been refuted.
Criticisms of these theories often focus on their reliance on insufficient evidence and their failure to fully capture the complexity of both gender identity and autism.