An individual with a typically male type of brain is more likely to have autism, according to a new study. 

A research team used magnetic resonance imaging (MRI) scans to examine individuals’ brains. They studied 98 adults with autism and 98 people with typically developed brains.

Professor Christine Ecker: her study supports the ‘extreme male brain theory’ of autism

Professor Christine Ecker, of Goethe University in Frankfurt, Germany, led the team. They looked at the thickness of the cortex, the brain’s outer layer. They then assessed the impact of the cortex’s thickness on the likelihood of a person having autism.

Thinner cortex in male brains

The cortex is embedded with nerves that are involved in memory, thinking, language and other higher cognitive functions. In men’s brains it is typically thinner than in women’s.

The team found that the thinner the cortex the more likely the person was to have autism.

The study found that women with typically male brain structures are three times more likely to have autism than those with the more usual female form.

Rates of autism among men are anywhere between two and five times higher than among women.

Thicker cortex protects women

The findings suggest that the thicker female cortex protects women against autism. Ecker has reportedly said that she and her colleagues are looking at other aspects of the cortex to support this idea.

Men with a thicker cortex, or typically female brain, have been found to be 1.2 times less likely to have autism than those with the more usual male form.

The researcher paper concludes: “Our findings suggest that the neurobiological male phenotype carries a higher intrinsic risk for ASD than the female phenotype across the binary categories dictated by biological sex.”

Extreme male brain theory

Reports suggest the study lends weight to the “extreme male brain theory” of autism.

This theory holds that autism is a kind of exaggerated maleness, making men more likely to have the condition. It suggests that typically masculine strengths such as mathematical and spatial reasoning are emphasised. These strengths come at the expense of female qualities such as empathy.

Professor Ecker and her team published their report in JAMA Psychiatry.

Published: 22 February 2017