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Female autism could be widely undetected because of gender bias in studies

Autism is believed to affect more men but women should also be in the picture. VikaUshkanova

Autism reveals itself in different ways in women than in men, according to new research from the University of Cambridge. And this has the potential to great advance our understanding of the condition.

Autism is estimated to affect 1% of the population and is believed to be more prevalent in males. As most studies have focused on this gender, this has led to a male-biased understanding of autism and, the Cambridge researchers say, the prevalence of female autism could be largely underestimated.

For this new study, equal samples of men and women were used to examine whether autism affects the brain of males and females in a similar or different way. Magnetic resonance imaging (MRI) scans were used to map the brains of people with and without autism.

The findings showed physiological differences in the brain between females with autism and those without were similar to those found between the sexes. For example, males tend to have a smaller anterior cingulate cortex than females. They found that this was also true of females with autism. This suggests that the effect of autism on the brain of females “shifts” them towards what would typically be expected to be found in males.

“Generally, it is considered that females with autism tend to be more severely affected,” Meng-Chuan Lai, who led the research, said. “They are thought to have more neurological problems, lower intellectual ability, and so on.”

“However, our research implies that this could be due to the fact that females with less severe autism might be under-recognised in clinics and in past research. Autism affects different parts of the brain in women, and therefore probably manifests itself differently.

"This raises the possibility that female autism is much more widespread than previously thought, but is undiagnosed.”

Simon Baron-Cohen, Professor of Developmental Psychopathology at Cambridge, was involved in the research and another study that investigated possible manifestations of female autism in people with anorexia. “Some females with anorexia may also have undiagnosed autism,” he said.

This male-bias in previous studies could explain the extreme sex ratio that is found across the Autistic Disorder Spectrum, which is thought to affect four males to every female.

This could have implications for the way we view and treat anorexia. Baron-Cohen explained that many women with anorexia - but who may not have autism - also have an above average number of autistic traits, which could point to a shared cause.

“This identifies aspects of functioning in people with anorexia that are not usually addressed,” he explained. “This could include their need for routine and predictability, their resistance to change, their narrow focus of interest and excellent attention to detail, their strong interest in patterns and systems, and their difficulties with social relationships and communication.”

But it’s still early days when it comes to making a direct link. “Whether some people with anorexia actually have a diagnosis of autism is unknown,” Meng-Chuan said. “In addition, to what extent autism is (mis)diagnosed with anorexia is also unknown. It may be too early to claim a definite link according to current evidence but this is certainly an area requiring more in-depth investigation.”

Sebastian Gaigg, a psychologist in City University’s Autism Research Group, said, “I would be surprised if this study did not become extremely influential in the field, as it raises a series of important new questions about the nature of gender differences in Autistic Spectrum Disorder.”

“As the authors note, much more research needs to be undertaken in this area and high-quality publications such as these will hopefully act as an important stimulant for this kind of work.”

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