'Male brains' linked to higher autism risk in women, study says
2/13/2017, 6 a.m.
(CNN) Brains, like faces, have features seen as either more masculine or more feminine. One feature of brain anatomy that is characteristic of males is associated with an increased risk of autism, according to a study published Wednesday in the Journal of the American Medical Association's Psychiatry edition.
Women with male characteristic brains are three times more likely to have autism than women with more "female" brains, the researchers say. Yet the reverse was not been proven true; no evidence indicates that men with more female-trait brains are less at risk for autism than men with typical brains.
Autism is considered a neurodevelopmental condition, which means symptoms begin early and children fail to achieve typical milestones of maturity at appropriate ages. Common symptoms include difficulty with communication and repetitive behaviors. In the United States, about one in 68 children has been identified with autism spectrum disorder, according to the Centers for Disease Control and Prevention.
The term "spectrum" refers to the fact that symptoms, levels of disability and positive skills may vary from person to person. For example, some people along the spectrum cannot make eye contact or follow simple directions, while others may be exceptional at math. And, as they age, some children with autism will learn to function more or less normally, while others will require substantial support to perform basic activities.
Autism spectrum disorder is two to five times more common in males than in females, according to Christine Ecker, lead author of the new study and a professor at Goethe University in Frankfurt, Germany. Though some researchers say sex differences in symptoms account for different rates of diagnosis, others hypothesize that sex-related variations in brain anatomy may contribute to the higher risk among males.
For the new study, Ecker and her co-authors examined whether brain anatomy differences led to a higher probability of autism in males. Specifically, they looked at cortical thickness: the depth of gray matter across the surface of the cortex.
"For example, it is known from previous studies that females tend to have a thicker cortex than males in various regions of the brain," Ecker wrote in an email. Previous studies have also shown thickness to be significantly altered in people with autism.
Study participants included 98 high-functioning adults with autism (49 of them men) and 98 adults without autism (51 of them men). Both groups were roughly within the same age range: mid-20s, on average.
The researchers excluded anyone with a history of psychiatric disorders, head injuries, certain genetic disorders or other medical conditions affecting brain function, such as epilepsy. People taking mood stabilizers and other medications were also excluded.
The researchers conducted MRI brain scans on each participant and then derived cortical thickness patterns for each using a software program. After anonymizing this information, Ecker and her colleagues made predictions about which participants were male or female based on cortical thickness and overall physical characteristics, also referred to as the "brain phenotype."
"We found that brain phenotype ranged from being typically female to typically male, and that there is variability between these extremes," Ecker said.