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Review
. 2012 Mar;9(3):751-7.
doi: 10.1111/j.1743-6109.2011.02567.x. Epub 2011 Dec 6.

Gender identity disorder in twins: a review of the case report literature

Gunter Heylens  1 , Griet De Cuypere, Kenneth J Zucker, Cleo Schelfaut, Els Elaut, Heidi Vanden Bossche, Elfride De Baere, Guy T'Sjoen
Affiliations
Review

Gender identity disorder in twins: a review of the case report literature

Gunter Heylens et al. J Sex Med. 2012 Mar.

Abstract

Introduction: The etiology of gender identity disorder (GID) remains largely unknown. In recent literature, increased attention has been attributed to possible biological factors in addition to psychological variables.

Aim: To review the current literature on case studies of twins concordant or discordant for GID.

Methods: A systematic, comprehensive literature review.

Results: 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). Of the seven opposite-sex twins, all were discordant for GID.

Conclusions: These findings suggest a role for genetic factors in the development of GID.

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