Summary

A widely cited 2022 brain-scan study by Kurth and colleagues reported that the brains of 24 transgender women, before hormone treatment, fell between those of men and women, though closer to men. This 2026 critique argues the key difference from men only looked real because of lenient statistical choices: testing in one direction only, and not adjusting for making three comparisons. With standard adjustments, the difference from men could easily be chance, though the difference from women still holds. Small groups and one unusual result make it fragile. Sexual orientation, known to relate to brain structure, was never analysed though the data existed. The critique is plausible but uses only published figures, was accepted nine days after it was sent in, and its lead author is a Manhattan Institute fellow on the journal's advisory board.

Key findings

• 2022년 연구는 남성 24명, 여성 24명, 아직 호르몬을 쓰지 않은 트랜스젠더 여성 24명을 뇌를 남성에서 여성까지의 하나의 척도로 점수화하는 컴퓨터 모델로 비교했습니다. 트랜스 여성의 뇌가 출생 성별에서 성별 정체성 쪽으로 이동해 있다고 결론지었습니다.
• 이 연구는 한 방향의 차이만 검정했습니다. 통상적으로 하듯 양방향을 검정하면 트랜스 여성 대 남성의 핵심 차이가 더 약해집니다. 비교가 세 번 이루어졌다는 점을 조정하면 우연일 가능성이 충분합니다.
• 트랜스 여성과 여성 사이의 더 큰 차이는 이런 조정 후에도 유지됩니다. 따라서 논쟁은 트랜스 여성의 뇌가 여성의 뇌와 다른가가 아니라 남성의 뇌와 다른가에 관한 것입니다.
• 집단당 24명뿐이어서 어떤 차이의 크기도 불안정합니다. 남성 집단의 비정상적인 결과 하나는 그것을 빼고 분석을 다시 돌려 확인한 적이 없습니다.
• 이 연구가 통계 방법을 정당화하려고 쓴 검정은 이만큼 작은 집단에서는 약합니다. 비판자들은 가정이 더 적은 방법도 최소한 보고되었어야 한다고 말합니다.
• 트랜스 여성 24명 중 6명은 남성에게, 18명은 여성에게 끌렸습니다. 성적 지향은 뇌 구조와 관련이 있고, 원저자들은 이 자료를 갖고 있었지만 고려하지 않았습니다.
• 비판자들은 각각 원본 자료를 거듭 요청했지만 답을 받지 못했으므로, 비판은 발표된 수치에 의존합니다. 이들은 자료를 공개하고 다른 사람들이 연구를 반복할 것을 요구합니다.

Abstract

Kurth et al. (2022) concluded that the brain anatomy of transgender women is shifted away from their biological sex and toward their gender identity. We evaluate whether the study’s evidence supports this conclusion by focusing on its statistical methods and treatment of sexual orientation in its analyses. The principal finding relies on a very small sample, a weak justification for parametric analyses, one-tailed post hoc tests, no correction for multiple comparisons, and limited robustness testing. The study also did not properly account for sexual orientation as a potential neuroanatomical confound despite having the relevant participant data to do so. These methodological choices consistently bias the results toward smaller p-values and stronger apparent support for the authors’ stated hypothesis. The evidence presented therefore does not justify the study’s headline conclusion.

Conclusion

The analyses presented do not adequately support the paper's headline conclusion that transgender women's brains are shifted toward their gender identity. The evidence used to support that conclusion is weakened by a series of methodological limitations and poor choices, including a small sample size, parametric statistical methods, one-tailed post hoc hypothesis tests without correction for multiple comparisons, and the absence of several robustness analyses. The study also does not address sexual orientation as a potential confound, despite the authors possessing both the neuroanatomical and sexual orientation data needed to evaluate this possibility. These methodological choices and omissions consistently strengthen the perceived support for the authors' stated hypothesis while weakening confidence in the reported findings. Given the paper's unusually broad influence in neuroscience, medicine, journalism, law, and public policy, the methodological issues warrant careful consideration before the study can be cited as evidence supporting the hypothesis, and the authors welcome a response from the original authors and encourage public release of the anonymized participant-level data so that the findings can be independently replicated and evaluated.