Why Is Autism More Common In Males?

On 30th January I went to a talk by leading Autism professional Prof. Simon Baron Cohen at Coventry University. I met up with our member Derrick who lives down this neck of the woods, went in together and joined fellow aspie Jo who travelled from Lancashire who Derrick knows from the Aspie Village forum.

Simon managed to fit into an hour, results from a range of research studies in order to shed light on the title of the talk. The findings generally show results on a scale with neurotypical female participants at one end of the scale, neurotypical male participants in between and those with Autism at the other end of the scale thus justifying the argument.

Simon started with a look at the latest Autism prevalence data from the Centers for Disease Control and Prevention (CDC) on children in the U.S. which shows 1 in 42 boys and 1 in 189 girls are on the Autism spectrum, giving a ratio of 4:1 (male:female). However due to variances in diagnostic criteria and early detection I suspect such figures would vary from country to country and similar research in the UK would show a slightly lower prevalence.

To summarise Simon’s discussion:
– Spontaneous Toy Choice study of infants at 12 months shows that girls are more likely to create social stories (e.g. playing with dolls) and boys are more likely to play with construction-based toys.
– In newborn babies, girls have shown to be more stimulated by people’s faces and boys more stimulated by cot mobiles. This stage of development is significant because as they are newborn they are not affected by gender conditioning. Children with Autism show more pronounced results in similar tests.
– Reading the Mind in the Eyes test (study where participants try to read a person’s mental state just from an image of someone’s eyes) shows neurotypical females being the most adept, with neurotypical males scoring lower, and Autistic individuals lower still, as one would expect. What is interesting is that there is little difference between males and females with Autism in their ability to do this. You can test yourself here! http://kgajos.eecs.harvard.edu/mite/
– Mechanical reasoning and attention to component parts in a system is much higher in AS.
– In a 2014 study looking at sex differences in scores on Simon Baron-Cohen’s authored Autism Quotient (AQ), Empathy Quotient (EQ), Systemising Quotient Revised (SQ-R), results correspond to predictions from the ”extreme male brain” (EMB) theory of autism (extreme scores on autistic traits and systemising, below average on empathising). His E-S model shows the relationship between empathy and systemising.
– Some studies show that the brains of children with Autism is consistently larger in volume at all age points from birth to 72 months and people with Autism have a larger Amygdala. After early adulthood brain volume progressively shrinks but in Autism it actually continues to grow.

He then talked in detail about the Cambridge-Denmark study looking at foetal testosterone levels. The reason to test this is that this hormone could explain the gender ratio in Autism. Of course, as Autism is not diagnosed until later in childhood or into adulthood it is impossible to obtain foetal testosterone data retrospectively, so fortunately the Danes have over 100,000 samples of amneotic fluid that they have been collecting since the 1980s. Out of those samples, the data for individuals who later received a diagnosis has been analysed against controls.

Results of this show:
– Boys have about twice the amount of testosterone in the womb than girls although there are a lot of individual differences.
– Testosterone has a masculinising effect on the body and the brain (in males and females).
– Higher levels result in less eye contact at 12 months, higher vocabulary at 18-24 months, more difficulty reading faces at 8 years and faster at spotting the part within the whole.
– Correlation between testosterone levels and child’s AQ scores (as answered by the parent).

Simon finished with some predictions which haven’t yet been tested. He says if females have more testosterone it could result in higher probability of hirsutism, irregular menstrual cycles, delayed menarche, severe acne, PCOS; these are all more common in females with Autism. He also would like more investigation into “tomboyism” in girls and the 2D:4D ratio (looking at lengths of fingers) which is significant to psychologists. There will be more studies on female-specific Autism as it is underresearched generally as well as other male-biased neurodevelopmental conditions to see if it can unlock more clues to the puzzle!