The problem is that research has emerged that questions whether these sex differences are all genetically based. Could it be that some of the differences reflect how the condition expresses itself in males and females? Could it be that we may be misdiagnosing some cases of autistic girls who are hiding, painfully in some cases, in plain sight?
One of the leading theories is that girls are protected from genetic disorders because of their extra X chromosome. The best evidence for this came in a 2014 study published in American Journal of Human Genetics in which researchers reported that girls with neurodevelopmental disorders actually have more genetic abnormalities—mutations and deletions of genetic material–than similar boys, but the conditions do not show up as readily. What this data seem to suggest is that the genetic threshold for ASD may be lower for boys than girls.