A Surplus of Males

I spent this Tuesday in Washington, reviewing autism research proposals.  I really enjoy that work, because it puts me among some of the best minds in autism science.   In the course of our discussions, an intriguing question arose.

We know autism is far more common in males, but the reason why remains elusive.  It’s one of those facts of autism that most people take for granted, and simply accept for what it is.  In earlier essays on this blog I have considered possible explanations, from Simon Baron Cohen’s theory that autism is “exaggerated maleness” to reasons why females might be undiagnosed and undetected.

All the explanations I have heard so far do not account for this interesting observation:

If the male/female ratio within a society is 50/50, any random group of families sould have a 50/50 distribution of sons and daughters.  Some families would have one child, others would have three.  Some would have all sons and others two daughters and a son.  Taken together, we would expect the total of sons and daughters to be equal.

If we assemble a collection of families in which there is at least one autistic child, that distribution of sons and daughters is not 50/50.  It favors the males.  Any autism researcher who has worked with families knows that to be true, even in the absence of hard studies to quantify it.  Why?

All of us know families that have all sons or all daughters.  We don’t make anything more of that that we do tossing a coin and having it come up heads three times in a row.  Just chance, we say.  But when you identify a group of families with a trait like autism, and they all have more sons than daughters . . . suddenly it stops looking random and starts to seem the result of something else. 

If this were a roll of the dice, you’d start to think the dice were loaded.

One explanation is that some parents have a son with autism and stop having children.  So the girls that might even the male/female ratio are never born.  I think that explanation may be true today, but what about the ages before modern birth control? 

Critics might say that we don’t know how autism was distributed among the sexes a hundred years ago, and that’s true.  The autism diagnosis has only existed for sixty-some years.  Yet we do have strong anecdotal evidence.  Using that, some modern day people have “diagnosed” historical figures with autism based on what we know of them and their lives.  How many of those individuals are female?  Almost none.

Those “post-mortem diagnoses” are certainly subject to challenge and I’m sure some are even wrong.  That said, they can’t all be wrong and the male-female ratio in the known historical record of autism remains strikingly tilted toward the male side. 

Geri Dawson suggested another possible explanation for the male-female imbalance.  What if girl embryos are actually more susceptible to some factor implicated in autism, but in a different way?  The factor that produces autistic baby boys might result in unsuccessful pregnancies when the fetus is female.  The result – fewer baby girls with autism are born.

To the best of my knowledge, no one has studied pregnancies in families with autism.  All that has been studied are the resultant children.  We don’t know how many miscarriages may have preceded or followed the birth of an autistic boy.  The incidence of miscarriage in general has been studied and it would be interesting to know if families with autism deviate from the norms in that regard.

The son-daughter imbalance certainly ties in with the Baron-Cohen “maleness” theory.  If autism indeed an expression of excessively male genetic material, that imbalance might result in more males being born in those families.

I spoke to several scientists and it became clear that this is one of those obvious questions that has never really been answered.  There is the general belief that autism families contain more males, but we have no hard data to illustrate the difference.  We also don’t have any multi generational data, which could shed light on the heritability of the condition.

In my own family, I have one child, a son with Asperger’s.  My father had many Aspergian traits, but he died before anyone thought to explore that possibility.  He had a brother, and no sisters.   His father also had a brother and no sisters.  His grandfather had three brothers and a sister.  Is there a pattern there that relates to autism?  I really don’t know.

It would be very interesting to see a study that addressed this question.  Perhaps a grad student somewhere will read this, and bring a research proposal to our next review meeting . . . .

Stranger things have happened.


jonathan said…
Stranger things have happened.

Yes, I agree, like a certain 9th grade dropout I know being appointed to review all of these scientific studies at taxpayer expense.
Unknown said…
I wonder about the same thing!

My sister has two boys, both have been diagnosed as being on the Autism spectrum. I believe both diagnoses have been changed to Asperger's...or at least high-functioning autism. I don't believe anyone in her husband's family has it - and though I often felt my father was a bit Aspergian, he was never officially diagnosed.

My own three children have not been diagnosed with any type of Autism disorder, but I've often thought my two boys had Aspergian traits (though mild). My youngest is a girl, and as of yet doesn't seem to display any of the traits.

My mother went to a lecture on Asperger's with my sister a couple years ago and felt that the Aspergian traits they described fit a lot of things about me growing up (and I'm a woman). I do think they'll find that women are often misdiagnosed and don't display symptoms the same way. Women communicate so much differently than men anyway - so I think it would make sense they would display different symptoms of Asperger's or the like.
John Robison said…
Jonathan, the reason I stopped offering comments on your blog is that the tone of your writing has turned 100% negative. Every essay you have is critical of someone or something. There is nothing positive to be read.

I know you think you would make a better science reviewer than me, and I have encouraged you to pursue that dream. The fact is, it's not an either-or situation where they would choose your or me. We are not the only autistic people in the world who are ready to do this, and there is room for more than one. You are welcome to offer yourself up to the funding organizations, and be judged by your performance. It is not necessary to knock me down to build yourself up.

Best wishes
Anonymous said…
Shut up, Mitchell. John has a much better idea of what's going on than you'll ever have. Like he said, you're completely negative and I know the reason why as does virtually everyone you consider to be an enemy.

John, I wouldn't put any stock in Baron-Cohen's "maleness" BS. It completely undermines females on the Spectrum and in the process undermines a real understanding of the Spectrum as a whole. I know several ladies who are peeved at this and I agree with them - to the point that it resulted in me giving Baron-Cohen an HMP award. It's rubbish and should be thrown in the bin.

Personally, I think when the whole Spectrum is fully understood the ratio difference will drop. I'm certain that many females are going undiagnosed. Once that's revealed, I'm hoping that someone will finally go after the sensory overload theory I hold to.
John Robison said…
TPLG, I think there are many undiagnosed females as well. I've written about that and indeed you and I have talked about it.

AS funded a study of roughly 700 families with autism to look at the chances of having more than one kid with autism. In that study, every sibling was evaluated for autism using a "gold standard" test like the ADOS.

Presumably, in that environment, the females with autism would be picked up. Yet the male-female ratio remained imbalanced even there.

The testing was done at age 2-4, long before boys would be geeks or girls be shy and cute.

Like I said, I really don't know the answer. The more you think of it, the more interesting the question is.
John Robison said…
One more thing to TLPG . . . I don't disagree that there are many undiagnosed females in the Asperger world.

The point of this story was that there is still a surplus of males in the autism-affected families, diagnosed or otherwise. Why the population imbalance?
Anonymous said…
Very interesting! I'm very involved in the autism community in my city and as I was reading this I started thinking about all of the families I know who have children with autism.
And yes, there is a predominance of boys in most of the families. I myself have 2 boys, one with autism.
I'd love to see some studies done on this as well. Thanks for the thought provoking post.
Wednesday said…
I'd just like to make the point that when looking at figures from history, there are far more male lives documented than female ones. It's natural that more males would be diagnosed retrospectively than females, simply because there are far more to examine.

That aside, interesting post, and food for thought.
scribeswindow said…
I've seen far more boys diagnosed with autism. In our therapy group for my son, they are all boys excepting one girl, but she's been diagnosed with PDD NOS. I have a younger daughter who is not on the spectrum. I always thought that it was to do with the X chromosome that supposedly protects females from lots of different things?
Darius said…
I believe that the reason why there are more males than females with autism is that there is a genetic link. Females have 2 X chromosomes while male has 1 X and 1 Y chromosome. There is something in the X chromosome that has a connection with autism. In females, they are able to obtain the replacement for the faulty gene in the X chromosome from the other X chromosome. But in males, this is not possible. Therefore for autistic girls, it is because both X chromosomes have the faulty genes in it.
Livinia Redlips said…
Have you ever heard of a link between a Choroid plexus cyst showing up on an ultrasound and the child having ASD?
Anonymous said…
"Using that, some modern day people have “diagnosed” historical figures with autism based on what we know of them and their lives. How many of those individuals are female? Almost none."

But that could simply be because females didn't tend to be honored in the historical record until fairly recently; they had much more constrained academic and professional choices that might've led to them even being documented in the historical record. So this argument is unconvincing to me.

One historical woman who I would speculate was undiagnosed with a spectrum condition was Alice B. Sheldon, who wrote sci-fi under the pen name James Tiptree, Jr. If you haven't read her biography by Julie Phillips, I really, really recommend it. (Aspie or no, she was a fascinating woman.)

That said, it may still be the case that males are overrepresented, and I'm really fascinated by possible autism/sex/gender links. I've always felt that my mind works more like a boy's than a girl's, and also felt more gender-fluid than other girls. But I wouldn't be convinced of it by examples available in the historical record.
As a woman diagnosed with AS and the mother of a daughter diagnosed with AS, it seems to me that you cannot necessarily attribute characteristics of a male with AS to a female with AS. If you are looking for a nice Norton, you wouldn't shop at a store selling only Harley Davidsons. Both are motorcycles, yet very different in construction and performance. And, if you are well-versed in the maintance of a Honda, you may not know all there is to know about a Matchless-- although they both have engines. So, if more is known/understood about males with AS, it doesn't mean there are simply less females with AS because we don't understand or see the way it is expressed in females. The therapist I work with once suggested to me that females may manifest symptoms differently because some of the other genetic hardwiring known to mark so many of our naturally existing gender differences alters the expression. Therefore, symptoms go unnoticed or are even dismissed. If women are naturally considered more social, more accomidating, and more language oriented-- do they have a leg-up on assimilation? Some of these questions are hard to pose to myself because they have a vague odor of different from the norm is "bad" whether male or female. And, I simply do not believe that. Tested ratios seem solid but I sometimes how we were defining our parameters to begin.
Thanks. You've actually inspired or maybe even insighted me to write a little in my own blog about my Asperger's. I sense a woman's experience and perspective may not be THAT different-- although subtly.
Yes, insighted not incited. Well, okay, that as well.

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