For this study we used data from five datasets:

  1. The UK Biobank cohort is a population-based cohort of approximately 500,000 participants that were recruited in the United Kingdom between 2006 and 2010.
  2. 23andMe, Inc. is a personal genetics company founded in 2006 that, as of May 2018, had genotyped more than 4 million customers who have consented to participate in research.
  3. The National Longitudinal Study of Adolescent to Adult Health (Add Health) originated as an in-school survey of a nationally representative sample of US adolescents enrolled in grades 7 through 12 during the 1994-1995 school year. Respondents are born between 1974 and 1983. For this study, data are available for up to are 4,755 individuals.
  4. The Molecular Genetic Study of Sexual Orientation (MGSOSO) is a study specifically focused on sexual orientation in males. The study includes mostly families with one or more homosexual brother. Overall, the sample included 1,077 homosexual and 1,231 heterosexual men.
  5. The Child and Adolescent Twin Study in Sweden (CATSS) is an ongoing longitudinal twin study targeting all twins born in Sweden since July 1, 1992. Since 2004, parents of twins are interviewed regarding the children’s somatic and mental health and social environment around the twins’ 9th or 12th birthdays. At age 15 and 18, twins and parents completed questionnaires that, in addition to assessments of somatic and mental health, include measures of personality development and psychosocial adaptation. For this study, data are available for up to 8,109 individuals.

23andMe’s contribution to the study

23andMe is a commercial company that specializes in providing individuals with analysis of their genetic makeup, including detailed information about ancestry, relatives, and predisposition to traits and diseases. 23andMe also has a robust, long-standing research arm with a unique model in which customers are given the option to consent to participate in research, and their large database of user genotypes and self-reported traits enables this genetic research. Because customers have the option to consent to participate in research, the 23andMe database is invaluable for scientific studies like ours. For instance, collaborating with 23andMe boosted our sample size and therefore we had more statistical power to find and replicate genetic associations in our study. The data provided by 23andMe also enabled us to understand the genetic relationship between same-sex sexual behavior and sexual attraction (since the UK Biobank did not include data on sexual attraction). Members of the 23andMe LGBTQ Community and Research Team also provided input on the interpretation of the study findings.

23andMe is a commercial company and does not provide individual level genetic data to external researchers without specific consent. In this case, 23andMe provided aggregate-level “summary statistics”, which were then combined with the summary UK Biobank results.

23andMe used an additional secondary consent form for questions about participants’ sexuality. All 23andMe data analyzed as part of this study was from people who had specifically accepted this secondary consent.

The full summary statistics for the 23andMe GWAS are provided to qualified researchers who enter into an agreement with 23andMe that protects participant privacy. Interested researchers should visit https://research.23andme.com/dataset-access/ for more information and to submit a request for the data.