Sibling Sex Ratio and Birth Order in Early-Onset Gender Dysphoric Adolescents

Bibliographic Data

ID8355294
AuthorsSebastian E E Schagen (0000-0001-5073-5695, Amsterdam UMC Location Vrije Universiteit Amsterdam), Henriette A Delemarre-van de Waal, Henriëtte A Delemarre‐van de Waal (Amsterdam UMC Location Vrije Universiteit Amsterdam), Ray Blanchard (0000-0002-4499-3521, Centre for Addiction and Mental Health), Peggy T Cohen-Kettenis (0000-0003-0921-0859, Amsterdam UMC Location Vrije Universiteit Amsterdam, corresponding author)
Year2012
Volume41
Issue3
Pages541-549
Publication date2012-06-01
Peer ReviewedYes
Open AccessYes
TypeARTICLE
VenueArchives of Sexual Behavior (JOURNAL)
Journal identifiersISSN: 0004-0002 • E-ISSN: 1573-2800
PublisherSpringer Science and Business Media LLC (PUBLISHER)
DOI10.1007/s10508-011-9777-6
PMID21674256
PMCIDPMC3338001
OpenAlexW2171861709
LanguageEN
Citations received26
References cited47

Several sibship-related variables have been studied extensively in sexual orientation research, especially in men. Sibling sex ratio refers to the ratio of brothers to sisters in the aggregate sibships of a group of probands. Birth order refers to the probands' position (e.g., first-born, middle-born, last-born) within their sibships. Fraternal birth order refers to their position among male siblings only. Such research was extended in this study to a large group of early-onset gender dysphoric adolescents. The probands comprised 94 male-to-female and 95 female-to-male gender dysphoric adolescents. The overwhelming majority of these were homosexual or probably prehomosexual. The control group consisted of 875 boys and 914 girls from the TRAILS study. The sibling sex ratio of the gender dysphoric boys was very high (241 brothers per 100 sisters) compared with the expected ratio (106:100). The excess of brothers was more extreme among the probands' older siblings (300:100) than among their younger siblings (195:100). Between-groups comparisons showed that the gender dysphoric boys had significantly more older brothers, and significantly fewer older sisters and younger sisters, than did the control boys. In contrast, the only notable finding for the female groups was that the gender dysphoric girls had significantly fewer total siblings than did the control girls. The results for the male probands were consistent with prior speculations that a high fraternal birth order (i.e., an excess of older brothers) is found in all homosexual male groups, but an elevated sibling sex ratio (usually caused by an additional, smaller excess of younger brothers) is characteristic of gender dysphoric homosexual males. The mechanisms underlying these phenomena remain unknown

Birth order · Developmental psychology · Environmental health · Population · Public health · Sex ratio · Sexual behavior · Sibling · Clinical Psychology · Demographic Trends and Gender Preferences · Genetic and Clinical Aspects of Sex Determination and Chromosomal Abnormalities · Medicine · Psychology · Sexual Differentiation and Disorders

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