Preprint Review Version 3 Preserved in Portico This version is not peer-reviewed

Structural, Functional, and Metabolic Brain Differences as a Function of Gender Identity or Sexual Orientation: A Systematic Review of the Human Neuroimaging Literature

Version 1 : Received: 26 June 2020 / Approved: 28 June 2020 / Online: 28 June 2020 (09:24:59 CEST)
Version 2 : Received: 26 August 2020 / Approved: 27 August 2020 / Online: 27 August 2020 (08:43:20 CEST)
Version 3 : Received: 7 April 2021 / Approved: 8 April 2021 / Online: 8 April 2021 (10:14:11 CEST)

A peer-reviewed article of this Preprint also exists.

Frigerio, A., Ballerini, L. & Valdés Hernández, M. Structural, Functional, and Metabolic Brain Differences as a Function of Gender Identity or Sexual Orientation: A Systematic Review of the Human Neuroimaging Literature. Arch Sex Behav (2021). https://doi.org/10.1007/s10508-021-02005-9 Frigerio, A., Ballerini, L. & Valdés Hernández, M. Structural, Functional, and Metabolic Brain Differences as a Function of Gender Identity or Sexual Orientation: A Systematic Review of the Human Neuroimaging Literature. Arch Sex Behav (2021). https://doi.org/10.1007/s10508-021-02005-9

Journal reference: Archives of Sexual Behavior 2021
DOI: 10.1007/s10508-021-02005-9

Abstract

This review systematically explored structural, functional, and metabolic features of the cisgender brain compared with the transgender brain before hormonal treatment and the heterosexual brain compared to the homosexual brain from the analysis of the neuroimaging literature up to 2018, and identified and discussed subsequent studies published up to March 2021. Our main aim was to help identifying neuroradiological brain features that have been related to human sexuality to contribute to the understanding of the biological elements involved in gender identity and sexual orientation. We analyze 39 studies on gender identity and 24 on sexual orientation. Our results suggest that some neuroanatomical, neurophysiological, and neurometabolic features in transgender individuals resemble those of their experienced gender despite the majority resembling those from their natal sex. In homosexual individuals the majority resemble those of their same sex heterosexual population rather than their opposite sex heterosexual population. However, it is always difficult to interpret findings with non-invasive neuroimaging. Given the gross nature of these measures, it is possible that more differences too subtle to measure with available tools yet contributing to gender identity and sexual orientation could be found. Conflicting results contributed to the difficulty of identifying specific brain features which consistently differ between cisgender and transgender or between heterosexual and homosexual groups. The small number of studies, the small-to-moderate sample size of each study, and the heterogeneity of the investigations made it impossible to meta-analyze all the data extracted. Further studies are necessary to increase the understanding of the neurological substrates of human sexuality.

Keywords

Brain; Neuroimaging; Transgender; Transsexual; Gender Identity; Homosexual; Heterosexual

Subject

BEHAVIORAL SCIENCES, Applied Psychology

Comments (1)

Comment 1
Received: 8 April 2021
Commenter: Maria Del C. Valdés Hernández
Commenter's Conflict of Interests: Author
Comment: The systematic review up to 2018 has been updated with information from articles published up to March 2021 indexed in Medline, which comply with the inclusion/exclusion criteria of the primary study.
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