Four out of five autism sufferers are male. Is something in men’s genes—or brain structure—causing the gap?

Is Autism a Male Disorder?

Wilczynski: Only one out of five children with autism is female.  Work by Dr. Simon Baron Cohen, at Cambridge, and others have said that the autistic brain is an "extreme male brain."  What does that mean?

Walsh:  I think at the root of your Wilczynski is how do we make sense of this degree to which males are affected so much more commonly than females.  Is there a genetic underpinning for that?  Is it an environmental one or does it have to do with differences in the male and the female brain?  And again, I don’t think we know the answer yet.  We originally looked for genetic causes maybe due to sex-linked genes, and that does not seem to obviously account for that large difference. And so that does begin to make you wonder whether there are some other differences between males and females, particularly maybe males just aren’t very good at social behavior to begin with and so they have a higher risk of autism on that basis. I certainly am here to say I represent at least one male who has much poorer social behavior than the woman, than my wife or my daughters. And so that might be along the lines of what he is suggesting or maybe some other potential answer to that.

Wilczynski:  Conversely, as we’ve noted already there is no blood test to diagnose autism and so we find that there are also times where females are under diagnosed.  A female who engages very infrequently socially is considered shy and so instead of being diagnosed at two or three she is not diagnosed at all or until she is much older and that is another area where we need diagnosticians to really be focusing.

Fischbach:  There is no question there are differences between male and female brains.  They are called sexual dimorphisms and you can point to different anatomical structures.  The question is: is this related to the male hormone testosterone or are there other compensatory differences. And I think that is still undecided. But there are clear differences between and some- and there may be protective factors in a female brain.  We just don’t know.

Bookheimer: I think that most of us wouldn’t believe that the main reason for the gender difference in autism is under diagnosis of girls.  I think that it’s generally that case that there are many, many, many more cases of males with autism. 

Wilczynski:  Absolutely.

Fischbach:  You know, at the high end of the spectrum, towards the Asperger’s side the ratio is 8 to 1 to 10 to 1.  It’s really quite dramatic.  The low end of the IQ spectrum it’s closer to 2 to 1 or 1 to 1, so there are really differences depending on what level of the severity of the disorder.

Walsh:  That is an excellent point and it may be the that the high-functioning autism spectrum disorders lie Asperger’s and the low-functioning autism spectrum disorders where there is severe language and cognitive impairment may be very different conditions. And it may be that this male bias... has to do with that high functioning condition and that there might be a stronger genetic component to the lower-functioning cases.

Fischbach:  For some reason girls may just compensate better and we just don’t understand.  It would be wonderful if we did understand how they did that.

Walsh:  That question of compensation may come as we understand the genetics better and we don’t know enough about the genetics yet to know, but as we understand more of the genetic risk factors then we can begin to ask the question: are there females that carry a genetic profile that should predispose them to autism but don’t get it, compared to males who have autism with a very similar sort of genetic risk profile. And so we hope to have the sort of tools to be able to ask those questions soon although we’re not quite there yet with the genetics.