Video version of this post at the end.

The big surprise for me in the new autism statistics that just came out from the United States Centers for Disease control is that the discrepancy between boys and girls has actually increased.  Now, boys are 4.6 times more likely than girls to have an identified autism spectrum disorder, instead of four times. And then I remembered that these numbers are actually from 2008.  I think that awareness that there are autistic women who are not named Temple Grandin has increased tremendously in the last four years, and I think that we will probably see a change in the other direction with the next set of data.

Why are do there appear to be so many more autistic boys than there are autistic girls?

The one factor that definitely plays a role is sexism.  You see some hint at this in the CDC report itself:

In all seven sites reporting data on intellectual ability, a higher proportion of females with ASDs had intellectual disability compared with males, although the proportions differed significantly (52% for females and 35% for males; p<0.01) in only one site (North Carolina). When data from these seven sites were combined, 150 (46%) of 328 females with ASDs had IQ scores or examiners' statements indicating intellectual disability compared with 608 (37%) of 1,653 males.

In other words, girls are less likely to be diagnosed with autism unless they also have intellectual disability.

Girls are less likely to be diagnosed with autism, even when they display the same degree of severity:

Ginny Russell explained: "Boys were more likely to suffer from severe autistic traits, whether diagnosed with an ASD or not. However, even with the severity of autistic traits held constant, boys were still significantly more likely to receive an ASD diagnosis than girls.

"Boys are more than four times more likely to have ASD and are clearly more likely to suffer from these types of symptoms. More interesting is our finding that even with symptom severity held constant, there is still a gender bias towards diagnosing boys. Our analysis suggests that girls are less likely to be identified with ASD even when their symptoms are equally severe." The researchers suggested that the popular conception of autism as a 'male' disorder may contribute to this bias. 

I tend to believe that the popularity of Simon Baron-Cohen's theory that autism represents an "extreme male brain" probably has something with the movement toward even more bias in favor of boys in diagnosis than was previously the case.  In England, where his work is about twice as influential as it is the United States, researchers  found men were nine times more likely to be autistic than women.

Also, testing seems to be biased to be favor of showing the kind of autistic traits boys are more likely to have, according to research done by Somer Bishop, Marisela Huerta, and Catherine Lord:

In focus groups, Huerta says, parents of girls often note that the questions don’t capture what is unusual or abnormal about their daughters’ play habits.

Unlike the stereotype of the boys with autism, girls with the disorder are often interested in imaginative play — obsessively so, in some cases. “You don’t expect to see a kid with autism being obsessed with a baby doll,” says Bishop.

Similarly, a girl with the disorder may be socially interested and motivated, but unsuccessful in forming relationships with her peers. “We get referrals from families who are frustrated because they know in their gut that something is not going well in terms of their child’s overall development, but can’t quite figure out why things are so hard for their girls,” Huerta says.

There do seem to be significant differences in the way that autism tends to manifest itself in men and women, although it's always to important not to take generalizations based on gender too seriously. 

But these differences do mean that is very important to have both male and female autistic representation.

I decided to focus on the good part about the new appointments to Interagency Autism Coordinating Committee, which is that there are three autistic members, and they are all brilliant and compassionate guys.  But they are all male, and that's a problem.

It's also a problem when autism projects include only autistic women and no autistic men, which they too often do.  These new numbers underscore for me the need to do more to involve more autistic men in our discussions, in our organizations and in our planning. 

In the video, I get into these sensitive issue in some more detail, and am probably somewhat more controversial. 

Click here to watch.

Click here to watch on YouTube.