Brains of People with Autism More Symmetrical than Neurotypicals, Scientists Find

The brains of people with autism are more symmetrical than those of neurotypical people, scientists have found.

Those with the developmental disorder were more likely to have a thicker cerebral cortex, the layer of gray matter covering the brain, in various parts of the organ, according to a study published in the journal Nature Communications.

In the average person, the left and right hemispheres of the brain are asymmetrical. But small studies in the past have indicated the different sides are more similarly sized in those with certain conditions, such as autism, as well as schizophrenia and dyslexia.

The latest study is the biggest to date on this topic, and saw an international team of scientists provide scans on the brains of 1,774 people with autism spectrum disorder and 1,809 neurotypical people who acted as controls. The information was taken from 54 separate datasets, collected over more than two decades.

Autism, or Autism Spectrum Disorder (ASD), is an umbrella term for conditions where people behave and communicate in ways different to those who are neurotypical. This can encompass speech, nonverbal communication and social skills, and see them demonstrate repetitive behavior.

By its nature, each individual has different strengths and challenges, according to Autism Speaks. While some can live independently and are highly skilled, others may experience severe challenges and require significant support in their daily lives.

Clyde Francks, a researcher at the Max Planck Institute Nijmegen who led the study, told Newsweek: "For the first time, we can be relatively confident that altered development of the brain's left-right asymmetry is affected in ASD, and we can see which brain regions are most affected."

Francks said: "Brain asymmetry is partly heritable and so is ASD, but it is not clear that some of the same genes affect both of these traits."

However, he highlighted: "The average differences are actually very subtle, so that the spread of data is largely overlapping between ASD and controls. So these brain differences are not, of themselves, useful biomarkers or clinical predictors of ASD. The value [of the study] is in better understanding the biology of the disorder."

Clyde also acknowledged the work has its limitations, including that it was based on many datasets and the results therefore reflect the average.

"It is possible that alterations of brain asymmetry might be stronger, or a different pattern of brain regions might be affected, when focusing on particular sub-groups of people with the disorder," he explained.

"ASD is an 'umbrella diagnosis' covering a set of related disorders, with various different causes for different people with the disorder," said Francks.

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Stock image illustration of a brain. Scientists have compared the brains of people with autism and neurotypical individuals. Getty