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The Difference in Autism Prevalence Rates Between Boys and Girls: Is it a Lack of Accurate Testing or Is There A Genetic Component To It?

Autism research

We all know that Autism seems to be more prevalent in boys than it is in girls. Most sources put the sex ratio in Autism at 4-to-1. Meaning that for every 4 Autistic boys there is 1 Autistic girl. But what leads to this difference? Is it a genetic component or are the major tools we are using to diagnose our Autistic individuals essentially rigged and unable to accurately differentiate between male and female subjects; leading to lower diagnosis in females than is accurate.


Everybody knows that “diagnosing Autism is expensive, it is also time consuming, so doctors use screening tools to filter out those people who are unlikely to be diagnosed as Autistic.” In fact, just raising an Autistic individual is expensive. Harvard researchers estimate that the added costs of Autism-related healthcare and education average more than $17,000 per child, per year in the United States. With the costs rising it seems an answer is needed now more than ever.

Researchers are digging deeper into this subject as we speak. There are multiple propositions for why there is a prevalence difference. Wired.com reports that, “men do seem to have a higher predisposition to developing Autism. It is reported that male fetuses seem to be more vulnerable to health problems in general.” The director of gender research at the Autism Research Centre in Cambridge, Meng-Chuan Lai, says “this vulnerability may result from hormonal disturbances related to sex differentiation, immunological development, and development of the gut microbes – all mechanisms thought to relate to the development of Autism.” Is it really the differences in fetuses or is it the tools we use to diagnose?

The reports go further to propose another option. Could it be that females have genetic protection? Alycia Halladay, chief science officer of the Autism Science Foundation, proposes there may also be a ‘female protective effect’ where Autism is concerned. “Girls with Autism certainly have a higher genetic load,” Halladay says. “So, you actually see more genetic mutations in girls with Autism than you see with boys with Autism.” Largely implying that girls are protected genetically. But is it more than this? Is it the actual tools that we use that cause some of the differences in prevalence rates?

Some researchers are leaning towards the difference in prevalence rates being the lack of accurate testing for females. To me it seems likely that this is the correct direction to be directing our efforts as “diagnostic and screening tools were developed with male samples” to begin with. Of course, they are going to have issues diagnosing Autism in females with a tool designed around males.

There are already known differences in the way Autism is exhibited in males and females. For example, women are found to be “better at hiding social and communicative difficulties.” Whereas men are “more likely to show obvious, and hence easier to detect, circumscribed interests” Researchers wanted to know whether 2 rating tools that are used picked up on these differences and if maybe this could lead to an explanation of the difference in the prevalence rates among genders.

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Since “screening and diagnostic tests focus on the most common, male manifestations of these core symptoms, females tend to be overlooked.” For example, narrowed “interests in males are more likely to be based on unusual topics.” Girls seem to be different in their narrowed interests, however. Girls and women may center their interests on things that common girls set their interests on. “Only the intensity of the interest sets them apart from non-Autistic females.”

So, researchers sat out to figure out if the tools we use are the cause. The first tool (and one that has been questioned in previous studies) is called the ‘Autism-Spectrum Quotient.’ The other, and the one that was of more focus, is called the Ritvo Autism Asperger Diagnostic Scale-Revised (RAADS-R), which is “a widely used questionnaire for assessing Autism in adults with average or above average intelligence.” To do so, researchers “compiled the RAADS-R scores of over 200 people who had a formal diagnosis of Autism.”

They then “compared scores between Autistic men and Autistic women on five different symptom areas:
- difficulties with social relationships
- difficulties with language
- unusual sensory experiences
- motor problems
- "circumscribed interests" (a tendency to have very strong, fixed interests).”

They were testing for the ability to diagnose girls using these tests. Their analysis showed that RAADS-R found no sex differences “in scores between Autistic men and women in social relatedness, language and circumscribed interests.” One possible explanation for this result is the way the RAADS-R test relies on its reporting. It depends on people accurately judging and reporting their own symptoms. As Autistic people often “lack insight into their own behavior” they may find it difficult to report their own symptoms accurately. It is possible that the gender differences that we see only appear when “behavior is diagnosed by an experienced clinician.” It is reported, however, that another likely reason for finding no sex difference in Autism traits is that most studies looking into this sort of thing “include Autistic people who have received a formal diagnosis through assessment with the very tools and tests they are investigating.” This might explain why fewer women tend to be diagnosed.

As more males than females have received a diagnosis of Autism, many of the theories we have about Autism are based on these diagnosed cases. Because of this much of our data may only apply to males. This needs to be investigated further. “Likewise, as we base our screening tools and diagnostic tools on males who have been diagnosed, we may only pick up women who show male-like symptoms.” It is noted that “we could be missing the women who have very different, more female presentations of Autism, but who still show the core features that are central to the diagnosis.”

These include problems with:
-social interaction
-restricted behavior and interests.

Don’t worry though, whether its genetics or the lack of having the right tools that is causing the difference in rates- this may soon be a problem of the past. It is reported that “efforts are now underway to develop screening tools that are better at identifying Autism in females.”