Research purporting to demonstrate that trans-identifying individuals’ brains resemble those of the opposite sex often ignores a major confo
By: Colin Wright, Samuel Stagg, Christina Buttons
Published: Mar 14, 2025
Earlier this week, City Journal published the tragic story of Yarden Silveira, a young detransitioner—someone who pursues hormonal and/or surgical “sex change” procedures but then seeks to reverse course—whose life ended abruptly after suffering severe complications from a gender-related genital surgery. What led Yarden to adopt a transgender identity in the first place? In 2014, after encountering the growing wave of pro-trans narratives in popular culture, Yarden told his family that he believed he had a “female brain.” Though initially uncertain, his mother was ultimately convinced by scientific papers that suggested that her son could have a female brain trapped in a male body, and that this mismatch caused him unimaginable distress.
“A trans woman (such as myself) was born with a male body, but she has always had her female brain. Literally born with a female brain,” Yarden wrote in 2016.
This belief was widespread back then—and it still is. On January 31, Wisconsin Public Radio featured an interview with a mother, Carri, concerned about President Trump’s new executive order banning federally funded medical and surgical “sex change” procedures for minors. Carri spoke about her daughter, who identified as transgender at 15 and was allowed to medically transition. She said, “Those hormones really helped match his brain with his body which, to me, that’s just the basic level of care we can provide individuals that identify as trans.”
The power of this narrative in persuading people to pursue, or to allow their children to pursue, irreversible medical procedures cannot be overstated. But the notion that males can have “female brains,” and vice versa, rests on a flawed interpretation of “brain sex” studies that in no way demonstrate or even suggest a definitive biological basis for “gender identity.” Little effort has been made to correct this misleading assertion.
The theory is advanced for relatively straightforward reasons. Civil rights lawyers, activists, and researchers contend that people who identify as transgender possess a “brain sex” misaligned with their physical body, thereby establishing a biological basis for “gender identity” akin to immutable traits like race. This framing carries significant legal weight, as U.S. civil rights law offers strong protections for characteristics considered “innate” or rooted in biology.
In courtrooms, prominent gender clinicians routinely invoke “brain sex” literature to bolster the perceived immutability and innateness of “gender identity.” For example, Daniel Shumer, a pediatric endocrinologist and clinical director of the Child and Adolescent Gender Clinic at Mott Children’s Hospital at Michigan Medicine, provided expert testimony in a case challenging Texas’s prohibition of “gender-affirming care” for minors. He linked “gender identity” to “brain structures,” arguing:
Scientific research and medical literature across disciplines demonstrates that gender identity, like other components of sex, has a strong biological foundation. For example, there are numerous studies detailing the similarities in the brain structures of transgender and non-transgender people with the same gender identity.
Such statements have become standard in legal battles over “gender-affirming care” and other trans-related policies. In Talbott v. Trump, a legal challenge to the president’s executive order barring transgender individuals from military service, Nicolas Talbott—a transgender-identifying female and activist—joined six active-duty service members and two prospective enlistees in arguing that “[s]trong research supports the conclusion that gender identity has a biological basis” and that “transgender women and non-transgender women have similar brain structures, specifically in the volume of the bed nucleus of the stria terminalis.”
Outside the courtroom, the idea of a brain-body mismatch has permeated popular culture, resonating with the “born this way” narrative embraced by many in the LGBT community. Mainstream television and other media have reinforced the concept. For instance, in a 2009 episode of Law & Order: Special Victims Unit, psychiatrist George Huang, played by B.D. Wong, explained that a trans-identified boy had a “female brain”: “For some children, something happens in utero where the brain develops as one gender and the body the other.” Children’s books have reinforced this idea, with the trans-identified protagonist in I Am Jazz declaring, “I have a girl brain but a boy body. This is called transgender. I was born this way!”
There is reason to believe the “brain sex” narrative has influenced many young people’s decisions to pursue medical transition. In a forthcoming survey conducted by coauthor Buttons, 49.2 percent of detransitioner respondents recalled health-care providers framing the respondents’ transgender identity as a brain condition, using phrases like “male brain in a female body,” or vice versa. In total, 85.7 percent of those surveyed said that their providers characterized transgender identity as an inherent, biological trait that required medical intervention.
To bolster these claims, providers often cite a growing body of scientific literature that purportedly validates the brain-body mismatch hypothesis. These studies claim that the neuroanatomy of people identifying as transgender more closely resembles the brain structures typical of the sex with which they identify, relative to non-transgender-identifying controls. Media amplified these findings, often presenting them as definitive proof that trans-identifying people “are who they say they are.” Headlines such as “Science Proves Transgender People Aren’t Making It Up” and “Transgender people are born that way, a new study has found” further entrench the narrative.
Proponents of these studies, however, rarely possess the expertise and background knowledge needed to examine their methods and conclusions critically. And the culturally charged atmosphere surrounding transgender issues means that facts often take a backseat to politically—and legally—expedient narratives.
The central flaw in current research purporting to validate the cross-sex brain hypothesis is an inconsistent—or complete lack of—control for individuals’ sexual orientation. Why does this matter? Because most people who identify as transgender are not exclusively heterosexual, and same-sex attraction has been linked to neuroanatomical differences that reflect a cross-sex shift—or, more broadly, to a reduction in typical sexual dimorphism (i.e., to having more androgynous brain structures). This raises serious methodological concerns about the extent to which sexual orientation might confound or interact with the neurobiological markers that “brain sex” studies routinely attribute to gender dysphoria. It also raises major ethical concerns about the use of “gender-affirming care” as a form of gay conversion therapy or as a maladaptive coping strategy for gay men.
If one properly controls for sexual orientation, the reported neuroanatomical shifts in transgender brain-scan studies diminish greatly or vanish entirely. To illustrate that point, consider three influential studies examining regional gray matter differences between transgender-identifying individuals and controls. These examples, considered together, illustrate a pervasive problem in the “brain sex” literature.
The first study, by Lajos Simon et al. and titled “Regional Grey Matter Structure Differences between Transsexuals and Healthy Controls—A Voxel Based Morphometry Study,” reported that trans-identifying individuals exhibit brain structures more closely resembling those of the opposite sex, relative to controls. This study is frequently cited as evidence supporting the brain-sex hypothesis. However, a different study by Eileen Luders et al. titled “Regional gray matter variation in male-to-female transsexualism,” which used similar neuroimaging techniques, found no significant differences overall in gray-matter volume between male-to-female (MtF) trans-identifying individuals and male controls. In one small brain region, the putamen, the MtFs did exhibit a cross-sex shift, relative to their dataset—i.e., putamen volumes in MtFs were larger and more similar to female controls—but this result is anomalous and incongruent with the findings of large-scale studies and meta-analyses demonstrating that males, not females, have larger putamen gray-matter volumes, on average.
A third study, by Ivanka Savic and Stefan Arver titled “Sex Dimorphism of the Brain in Male-to-Female Transsexuals,” comprehensively analyzed structural brain differences using MRI. While the authors observed some structural differences in the brains of trans-identifying men compared with those of non-trans-identifying male controls, these differences did not align neatly with a feminization pattern. Instead, the variations were distinct from typical male or female brain structures, suggesting a unique neuroanatomical profile rather than a simple cross-sex shift. Importantly, Savic and Arver controlled for participants’ sexual orientation and found that, when they did so, the brain differences attributed to gender dysphoria were much less pronounced.
A clear pattern emerges when comparing these and similar studies: the magnitude of the cross-sex shift reported in trans-identified individuals’ brains correlates with the proportion of homosexuals in the sample. For example, in Simon et al.’s study, all transgender participants were homosexual, potentially amplifying participants’ sex-atypical neuroanatomical features. In contrast, Luders et al.’s cohort had a much lower proportion of homosexual participants, coinciding with null findings overall regarding brain feminization. Savic and Arver’s rigorous control for sexual orientation further demonstrates that some neuroanatomical differences previously attributed to gender dysphoria likely reflect—or are confounded by—sexual orientation-related brain variations.
Popular “transgender brain” studies, in short, often fail to control for sexuality, undermining the claim that people with transgender identities have brains that more closely resemble those of the opposite sex.
What would it mean if the “transgender brain” hypothesis were true, and properly controlled studies did document a statistically significant cross-sex shift in the brains of people who identify as transgender? It would not logically follow that a brain scan can capture a person’s “gender identity”—just as brain scans cannot ascertain a person’s sexuality. Differences in group averages do not mean that every individual within a group shares those characteristics. Populations contain variance; for instance, some straight men exhibit brain structures that skew feminine, while some gay men exhibit brain structures that skew masculine. Brain scans therefore cannot verify whether a person is homosexual; nor could they verify whether a person “is transgender.” Brains, like most physical traits apart from primary sex organs, are not discretely sexed; they simply exhibit average differences between the sexes.
Even if there were compelling evidence for “brain sex,” gender clinicians, though often expressing strong confidence in the hypothesis, would be the last to advocate for the use of objective brain scans to validate their claims. Their hesitancy has roots in the history of sexuality research. When scientists proposed the existence of a “gay brain,” many gay rights advocates strongly objected, citing its potential for eugenic abuse (imagine, for example, a drug company developing a fetal “treatment” to “cure” homosexuality based on such findings). Despite progressives’ deep pessimism about science’s potential for abuse, however, many activists still peddle the “brain sex” narrative.
Notably, even though homosexuality is associated with a cross-sex shift in certain brain structures, activists avoid claiming that gays and lesbians exhibit a brain-body mismatch. This avoidance highlights a striking inconsistency in the application of the “brain sex” narrative. For decades, research has shown that homosexuals exhibit subtle neuroanatomical differences that trend toward patterns typical of the opposite sex. Yet, proponents of LGBT rights have rejected the notion that these differences imply a pathological misalignment requiring medical correction.
The persistence of the “brain sex” narrative has real and sometimes tragic consequences. For individuals like Yarden Silveira, it contributed to life-altering—and ultimately life-ending—medical decisions based on a flawed understanding of the science. The notion that transgender identity is rooted in immutable brain structure has led countless young people to undergo unnecessary and often harmful medical treatments, frequently without fully informed consent or consideration of alternative approaches. Challenging that notion isn’t just an academic exercise—it’s a necessary step toward protecting vulnerable individuals from medical abuse.
Policymakers should mandate rigorous, independent reviews of the scientific claims surrounding transgender identity’s supposedly biological basis. This review should include scrutinizing studies that promote the “transgender brain” hypothesis, and incorporate evidence from desistance and detransition research, which highlight how transgender identities are often transient.
Public-health policies must be grounded in comprehensive and unbiased research. Otherwise, vulnerable young people will continue to face irrevocable and potentially devastating treatments.
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It's funny how there are supposedly no differences between males and females when it comes to sports, and yet there are supposedly MRI-detectable "male brains" and "female brains."
🤔
This ideology is completely incoherent.
It's astonishing how many formerly reputable scientific institutions have embraced abject pseudoscientific gobbledygook.
