psychotherapy is based on the following scientific facts: Same-sex sexual attractions, behavior, and orientations per se are normal and positive variants of human sexuality; in other words, they are not indicators of mental or developmental disorders. Homosexuality and bisexuality are stigmatized, and this stigma can have a variety of negative consequences (e.g., minority stress) throughout the life span (D'Augelli & Patterson, 1995; DiPlacido, 1998; Herek & Garnets, 2007; Meyer, 1995, 2003). Same-sex sexual attractions and behavior can occur in the context of a variety of sexual orientations and sexual orientation identities (Diamond, 2006; Hoburg et al., 2004; Rust, 1996; Savin-Williams, 2005). Gay men, lesbians, and bisexual individuals can live satisfying lives as well as form stable, committed relationships and families that are equivalent to heterosexual relationships in essential respects (APA, 2005c; Kurdek, 2001, 2003, 2004; Peplau & Fingerhut, 2007). There are no empirical studies or peer-reviewed research that support theories attributing same-sex sexual orientation to family dysfunction or trauma (Bell et al., 1981; Bene, 1965; Freund & Blanchard, 1983; Freund & Pinkava, 1961; Hooker, 1969; McCord et al., 1962; D. K. Peters & Cantrell, 1991; Siegelman, 1974, 1981; Townes et al., 1976). Causes Biological vs. environmental determinants Although scientists favor biological models for the cause of sexual orientation, they do not believe that the development of sexual orientation is the result of any one factor. They generally believe that it is determined by a complex interplay of biological and environmental factors, and is shaped at an early age. There is considerably more evidence supporting nonsocial, biological causes of sexual orientation than social ones, especially for males. There is no substantive evidence which suggests parenting or early childhood experiences play a role with regard to sexual orientation. Scientists do not believe that sexual orientation is a choice. The American Academy of Pediatrics stated in Pediatrics in 2004: The American Psychological Association, American Psychiatric Association, and National Association of Social Workers stated in 2006: "Gay genes" Despite numerous attempts, no "gay gene" has been identified. However, there is substantial evidence for a genetic basis of homosexuality, especially in males, based on twin studies; some association with regions of Chromosome 8, the Xq28 locus on the X chromosome, and other sites across many chromosomes. Starting in the 2010s, potential epigenetic factors have become a topic of increased attention in genetic research on sexual orientation. A study presented at the ASHG 2015 Annual Meeting