Causes of gender incongruence

Gender incongruence is the state of having a gender identity that does not correspond to one's sex assigned at birth. This is experienced by people who identify as transgender or transsexual, and often results in gender dysphoria.^[1] The causes of gender incongruence have been studied for decades.

Transgender brain studies,^[2] especially those on trans women attracted to women (gynephilic), and those on trans men attracted to men (androphilic), are limited, as they include only a small number of tested individuals.^[3] Studies conducted on twins suggest that there are likely genetic causes of gender incongruence, although the precise genes involved are not known or fully understood.^[4]^[5]^[6]

^ Curtis R, Levy A, Martin J, Playdon ZJ, Wylie K, Reed R, Reed R (March 2009). "Transgender experiences – Information and support" (PDF). NHS. p. 12. Archived from the original (PDF) on 6 January 2012. Retrieved 2012-07-01.
^ Altinay, Murat; Anand, Amit (2020). "Neuroimaging gender dysphoria: a novel psychobiological model". Review. Brain Imaging and Behavior. 14 (4): 1281–1297. doi:10.1007/s11682-019-00121-8. ISSN 1931-7565. PMID 31134582. S2CID 167207854.
^ Guillamon A, Junque C, Gómez-Gil E (October 2016). "A Review of the Status of Brain Structure Research in Transsexualism". Archives of Sexual Behavior. 45 (7): 1615–48. doi:10.1007/s10508-016-0768-5. PMC 4987404. PMID 27255307.
^ Heylens G, De Cuypere G, Zucker KJ, Schelfaut C, Elaut E, Vanden Bossche H, et al. (March 2012). "Gender identity disorder in twins: a review of the case report literature". The Journal of Sexual Medicine. 9 (3): 751–7. doi:10.1111/j.1743-6109.2011.02567.x. PMID 22146048. Of 23 monozygotic female and male twins, nine (39.1%) were concordant for GID; in contrast, none of the 21 same‐sex dizygotic female and male twins were concordant for GID, a statistically significant difference (P = 0.005)... These findings suggest a role for genetic factors in the development of GID.
^ Diamond M (2013). "Transsexuality Among Twins: Identity Concordance, Transition, Rearing, and Orientation". International Journal of Transgenderism. 14 (1): 24–38. doi:10.1080/15532739.2013.750222. S2CID 144330783. Combining data from the present survey with those from past-published reports, 20% of all male and female monozygotic twin pairs were found concordant for transsexual identity... The responses of our twins relative to their rearing, along with our findings regarding some of their experiences during childhood and adolescence show their identity was much more influenced by their genetics than their rearing.
^ Besser M, Carr S, Cohen-Kettenis P, Connolly P, de Sutter P, Diamond M, Di Ceglie D, Higashi Y, Jones L, Kruijver F, Martin J, Playdon Z, Ralph D, Reed T, Reid R, Reiner W, Swaab D, Terry T, Wilson P, Wylie K (2006). "Atypical Gender Development – A Review". International Journal of Transgenderism. 9 (1): 29–44. doi:10.1300/J485v09n01_04. ISSN 1553-2739.

[1] Curtis R, Levy A, Martin J, Playdon ZJ, Wylie K, Reed R, Reed R (March 2009). "Transgender experiences – Information and support" (PDF). NHS. p. 12. Archived from the original (PDF) on 6 January 2012. Retrieved 2012-07-01.

[:3-2] Altinay, Murat; Anand, Amit (2020). "Neuroimaging gender dysphoria: a novel psychobiological model". Review. Brain Imaging and Behavior. 14 (4): 1281–1297. doi:10.1007/s11682-019-00121-8. ISSN 1931-7565. PMID 31134582. S2CID 167207854.

[Guillamon_2016-3] Guillamon A, Junque C, Gómez-Gil E (October 2016). "A Review of the Status of Brain Structure Research in Transsexualism". Archives of Sexual Behavior. 45 (7): 1615–48. doi:10.1007/s10508-016-0768-5. PMC 4987404. PMID 27255307.

[heylens_et_al-4] Heylens G, De Cuypere G, Zucker KJ, Schelfaut C, Elaut E, Vanden Bossche H, et al. (March 2012). "Gender identity disorder in twins: a review of the case report literature". The Journal of Sexual Medicine. 9 (3): 751–7. doi:10.1111/j.1743-6109.2011.02567.x. PMID 22146048. Of 23 monozygotic female and male twins, nine (39.1%) were concordant for GID; in contrast, none of the 21 same‐sex dizygotic female and male twins were concordant for GID, a statistically significant difference (P = 0.005)... These findings suggest a role for genetic factors in the development of GID.

[diamond-2013-5] Diamond M (2013). "Transsexuality Among Twins: Identity Concordance, Transition, Rearing, and Orientation". International Journal of Transgenderism. 14 (1): 24–38. doi:10.1080/15532739.2013.750222. S2CID 144330783. Combining data from the present survey with those from past-published reports, 20% of all male and female monozygotic twin pairs were found concordant for transsexual identity... The responses of our twins relative to their rearing, along with our findings regarding some of their experiences during childhood and adolescence show their identity was much more influenced by their genetics than their rearing.

[:0-6] Besser M, Carr S, Cohen-Kettenis P, Connolly P, de Sutter P, Diamond M, Di Ceglie D, Higashi Y, Jones L, Kruijver F, Martin J, Playdon Z, Ralph D, Reed T, Reid R, Reiner W, Swaab D, Terry T, Wilson P, Wylie K (2006). "Atypical Gender Development – A Review". International Journal of Transgenderism. 9 (1): 29–44. doi:10.1300/J485v09n01_04. ISSN 1553-2739.

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