Archives of Sexual Behavior

, Volume 40, Issue 3, pp 505–510

Birth Order and Ratio of Brothers to Sisters in Spanish Transsexuals

Authors

    • Unidad de Identidad de Género, Instituto Clínic de Neurociencias, Servicio de Psiquiatría, Hospital ClínicUniversidad de Barcelona
    • Department of Psychiatry, Institute Clinic of Neurosciences, Hospital ClínicUniversity of Barcelona
  • Isabel Esteva
    • Unidad de Trastornos de Identidad de Género, Servicio de EndocrinologíaHospital Carlos Haya
  • Rocío Carrasco
    • Unidad de Trastornos de Identidad de Género, Servicio de GinecologíaHospital Carlos Haya
  • M. Cruz Almaraz
    • Unidad de Trastornos de Identidad de Género, Servicio de EndocrinologíaHospital Carlos Haya
  • Eduardo Pasaro
    • Departamento de PsicobiologíaUniversidad de A Coruña
  • Manel Salamero
    • Unidad de Identidad de Género, Instituto Clínic de Neurociencias, Servicio de Psiquiatría, Hospital ClínicUniversidad de Barcelona
  • Antonio Guillamon
    • Departamento de PsicobiologíaUNED
Original Paper

DOI: 10.1007/s10508-010-9614-3

Cite this article as:
Gómez-Gil, E., Esteva, I., Carrasco, R. et al. Arch Sex Behav (2011) 40: 505. doi:10.1007/s10508-010-9614-3

Abstract

Three Western studies have shown that male-to-female (MF) homosexual transsexuals tend to be born later than their siblings and to come from sibships with more brothers than sisters. The objective of this study was to determine whether these variables would be replicated in 530 MF and female-to-male (FM) Spanish transsexuals according to sexual orientation. The results showed that MF homosexual transsexuals had significantly more older brothers than the non-homosexual MF group. Compared with the expected rates in the general population, birth order was significantly higher in both MF (Slater’s Index = 0.59; Fraternal Index = 0.61; Sororal Index = 0.58) and FM homosexual transsexuals (Slater’s Index = 0.65; Fraternal Index = 0.68; Sororal Index = 0.67), and sibling sex ratio was significantly higher than expected in homosexual MF (sex ratio = 0.55) but not in homosexual FM transsexuals. No significant differences were found in the non-homosexual subgroups. The replication of the later birth order and sibling sex-ratio effect in MF homosexual transsexuals corroborates previous findings in a variety of groups from different cultures and may suggest a common mechanism underlying the etiology of transsexualism.

Keywords

Birth order Sibling sex ratio Gender identity disorder Transsexualism Sexual orientation

Copyright information

© Springer Science+Business Media, LLC 2010