Genetic and Environmental Effects on Same-sex Sexual Behavior: A Population Study of Twins in Sweden
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There is still uncertainty about the relative importance of genes and environments on human sexual orientation. One reason is that previous studies employed self-selected, opportunistic, or small population-based samples. We used data from a truly population-based 2005–2006 survey of all adult twins (20–47 years) in Sweden to conduct the largest twin study of same-sex sexual behavior attempted so far. We performed biometric modeling with data on any and total number of lifetime same-sex sexual partners, respectively. The analyses were conducted separately by sex. Twin resemblance was moderate for the 3,826 studied monozygotic and dizygotic same-sex twin pairs. Biometric modeling revealed that, in men, genetic effects explained .34–.39 of the variance, the shared environment .00, and the individual-specific environment .61–.66 of the variance. Corresponding estimates among women were .18–.19 for genetic factors, .16–.17 for shared environmental, and 64–.66 for unique environmental factors. Although wide confidence intervals suggest cautious interpretation, the results are consistent with moderate, primarily genetic, familial effects, and moderate to large effects of the nonshared environment (social and biological) on same-sex sexual behavior.
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- Genetic and Environmental Effects on Same-sex Sexual Behavior: A Population Study of Twins in Sweden
Archives of Sexual Behavior
Volume 39, Issue 1 , pp 75-80
- Cover Date
- Print ISSN
- Online ISSN
- Springer US
- Additional Links
- Sexual behavior
- Sexual orientation
- Population survey
- Twin study
- Industry Sectors
- Author Affiliations
- 1. Centre for Violence Prevention, Karolinska Institutet, P.O. Box 23000, 104 35, Stockholm, Sweden
- 2. School of Biological Sciences, Queen Mary-University of London, London, UK
- 3. Institute of Psychiatry, King’s College-University of London, London, UK
- 4. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden