Study: Why Some Transgendered People Have Higher Levels of Autistic Traits

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Photo-Illustration by Alexander Ho for TIME; Brain: Getty Images

Female-to-male transgendered people — known as transmen — have more autistic traits than typical heterosexual men and women, and more than those who wish to switch gender in the opposite direction, according to new research.

Scientists led by Simon Baron-Cohen, a professor of developmental psychopathology, at Cambridge University looked for autistic traits, such as problems parsing social signals and difficulty in dealing with changes in routine, in 61 transmen, 198 transwomen, 98 typical females, 76 typical males and 125 people with actual diagnoses of Asperger’s syndrome, a mild form of autism.

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“Those in the female-to-male group scored above average in terms of the number of autistic traits,” says Baron-Cohen. Indeed, the transmen outscored all but those with Asperger’s diagnoses on the Autism Spectrum Quotient, a scale devised by Baron-Cohen.

Baron-Cohen has long theorized that people with autism may have what he calls an “extreme male” brain — dominated by a style of thinking called “systemizing,” which focuses on predictable patterns like those found in mathematics or mechanical devices. He contrasts this with a cognitive style called “empathizing,” which allows for better understanding of the minds and emotions of others.

Typically, women do better at empathizing and men at systemizing, but there is, of course, wide variability: some women outperform men at systemizing, and some men are better empathizers than women.

Why the difference? Baron-Cohen and his colleagues recently found that giving testosterone to women decreases their ability to empathize, particularly among women whose bodies show evidence that they were exposed to higher levels of testosterone in utero. And previous research has linked high levels of testosterone in the womb to autistic traits. (Interestingly, in-utero exposure to testosterone can be estimated by looking at the ratio between the length of the ring finger and index finger.)

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But because the transmen in the study had already transitioned to their preferred gender — a process that requires taking male hormones — the research could not show whether their autistic traits resulted from the hormones or led to the desire to change gender in the first place.

Baron-Cohen says the idea for his study arose when one of his collaborators, Dr. Domenico Di Ceglie, a child psychiatrist who directs the Gender Identity Development Service at London’s Tavistock Clinic, observed that the girls he was seeing with gender identity problems seemed to have more autistic traits than he expected.

“He thought [that their focus on changing gender] might be similar to some of the very strong fixed beliefs you see in people with high levels of autistic traits,” says Baron-Cohen, explaining that girls with more autism-related traits may also find that they share more interests with boys.

Similarly, some people who focus compulsively on eating — symptoms that are characteristic of anorexia — may also be driven by an underlying obsessive nature that turns in that direction. Past research has suggested that some cases of anorexia may in fact be attributed to girls with Asperger’s developing an obsession with being thin.

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Baron-Cohen is quick to say that these findings do not mean that the gender identity issue for transmen is just another autistic obsession like an interest in railroads — but that understanding these kinds of connections could lead to better care for people with both conditions.

His co-author, Emma Martin, herself a transwoman, said in a statement, “This new research reminds us that gender incongruence is incredibly complex. Every possibility should be discussed with new clients, but should not delay what can be a painfully slow process for those affected.”

The study was published in the Journal of Autism and Developmental Disorders.