Sexual orientation is a multidimensional personal framework composed of sexual identity (the self-assigned label), sexual behavior (the gender of partners), and sexual attraction (an individual’s attractions to the same or opposite sex).¹,² Sexual orientation is not discrete—individuals tend to fall along a continuum of sexual expression and desires rather than into distinct categories. These dimensions may not be in full concordance, reflecting the diversity of intimate human relationships. The phrase sexual preference implies choice and should not be used in reference to sexual orientation.

Gender identity relates to an individual’s innate sense of maleness or femaleness and should not be confused with or used interchangeably with sexual orientation. It usually develops at a much younger age (see Chapter 39).

Although there is no absolute definition, homosexuality usually reflects “a persistent pattern of homosexual arousal accompanied by a persistent pattern of absent or weak heterosexual arousal.”³ Most homosexual individuals have a gender identity that is consistent with their biologic sex. Homosexuality is recognized as a nonpathologic variant of human sexuality.⁴ Homosexual men are often informally referred to as “gay,” while women may be referred to as “gay” or “lesbian.”

A bisexual person is erotically attracted to both men and women. This does not preclude long-term monogamous relationships, nor does it imply promiscuity.

Complicating all of the definitions above is the fact that the dimensions of sexual orientation (identity, behavior, and attraction) may occur in ways that seem contradictory to health care providers or others. Lesbian, gay, or even “queer” is a sexual identity label a person may or may not adopt. A person need not have had sex with a person of the same gender to identify as lesbian or gay, and a person who is sexually active with partners of the same gender may not identify as lesbian or gay. Young people who engage in sex with persons of the same gender may identify as homosexual or bisexual, but sometimes as heterosexual, curious, or questioning. Today, the term “sexual minority” or “queer” may be used to refer to the lesbian, gay, bisexual, and transgender populations collectively.

In a large, population-based study of 35,000 junior and senior high school students in Minnesota,⁶ greater than one-fourth of 12-year-old students were unsure about their sexual orientation. By 18 years of age, the figure dropped to 5% and uncertainty gave way to heterosexual or homosexual identification. Reported homosexual attractions (4.5%) exceeded fantasies, the latter being more common in girls (3.1%) than in boys (2.2%). Overall, 1.1% of students described themselves as predominantly homosexual or bisexual. The prevalence of reported homosexual experiences remained constant
among girls (0.9%), but increased from 0.4% to 2.8% in boys between the ages of 12 and 18 years. Childhood and adolescent sexual behavior is not necessarily predictive of an adolescent’s sexual orientation. Only about a third of teens who reported homosexual experience or fantasies identified themselves as homosexual or bisexual. Complicating the matter is that some children who have had involuntary or coercive same-gender sex may experience confusion about their sexual orientation as AYAs. A study by Garofalo et al.,⁷ based on a question added to the Massachusetts Youth Risk Behavior Survey, found that 2.5% of youth self-identified as gay, lesbian, or bisexual. There is a growing recognition that youth who are “unsure” of their sexual orientation make up a sizeable number of youth⁶ with unique stresses and morbidity.

The National Health and Social Life Survey (NHSLS) of 1992 used several dimensions of sexuality, including behavior, desire, and identification.⁸ The prevalence of homosexual contact since puberty was approximately 10% of men and 5% of women, and 5% and 4%, respectively, had had homosexual contact since age 18 years. Because estimates in this study were based on small sample sizes, the numbers have been questioned in this sample. A more recent survey, the National Survey of Sexual Health and Behavior (2010),⁹ estimates that 6.8% of men and 4.5% of women identify as homosexual, gay, lesbian, or bisexual, but did not ask questions on same-sex desire. The National College Health Assessment,¹⁰ which surveys YAs who are college students, asked questions about multiple dimensions of sexuality, including attraction, behavior, and identity. The most recent survey data available suggest that almost 3.0% of YAs identify as lesbian or gay and almost 5.0% identify as bisexual.¹⁰ A sizeable minority (2.5%) still identified as unsure.¹⁰

The clustering of homosexuality within some families has long been recognized. As compared to dizygotic twins, the greater concordance of homosexuality in monozygotic twins highlights the role of genetic constitution. Among identical twins, concordance rates for homosexuality are reported in the range of 48% to 66%. A chromosomal location (Xq28) has been identified and is thought to be involved in male homosexuality; a specific gene has not yet been identified. No clear patterns of inheritance have been established.¹¹

Although heterosexual and homosexual adults have comparable levels of circulating sex steroids, it has been proposed that perinatal hormones organize and activate key areas of the brain early in life. This might contribute to the eventual development of neuroanatomical and neuropsychological functional differences related to sexual orientation.

Brain: Genetic, hormonal, and other biologic factors may influence behavior by their effect on the structure and functioning of the brain. In humans, brain regions correlated with homosexuality include the interstitial nuclei of the anterior hypothalamus (designated INAH1, INAH2, INAH3, and INAH4), the supraoptic nucleus, the anterior commissure, and the corpus callosum. The evidence is quite limited, and findings vary among studies.

Less well understood is the way that biology interacts with the environment and experience in shaping the expression of sexual orientation. Well-designed studies have not found differences in the familial and social backgrounds of homosexual and heterosexual men and women, nor any evidence that homosexuality is related to abnormal parenting, sexual abuse, or other traumatic events. Indeed, knowledge of other homosexual individuals is not necessary for the development of a homosexual orientation,¹² nor do homosexual parents have an influence on the sexual orientation of their children.¹³ However, environment can modulate the expression of fundamental biologic predisposition by influencing the social behavior and visibility of homosexual persons, complicating whether environmental factors are the result, rather than the cause.

Early descriptions of sexual orientation identified stages of acquisition of a homosexual identity (sensitization, identity confusion, identity assumption, commitment).¹⁴,¹⁵ This appears to be an effect of a previous age cohort defined by events that were occurring. More recent research has identified that critical aspects of sexual orientation develop during preadolescence, typically as a period of sexual questioning which is relatively well adjusted, and not influenced by stigma.¹⁶

Prior research found that gay and lesbian adolescents generally reported first awareness of same-sex attractions by 10 or 11 years of age, self-identification as homosexual at age 13 to 15 years, and first same-sex experiences near the time of self-identification.¹⁷ Self-identification usually precedes sexual debut with either male or female partners.¹⁸ Girls appear to “come out” later, in the context of a relationship; whereas boys appear to come out at a younger age, in the context of sexual encounters.¹⁸,¹⁹ With increasing visibility of sexual minority role models for adolescents, young people may be more likely to self-identify as a sexual minority before sexual debut.²⁰ As more population-based surveys are available, it is clear that self-identification likely varies by race, ethnicity, income level, or geographic location.⁵

The risk of breast cancer and its complications among lesbians may be heightened by nulliparity, delayed pregnancy, alcohol use, obesity, and nonuse of screening services. This is an area of ongoing research. Ovarian, lung, and colorectal cancers have been virtually unexplored in LGB communities.²⁶

Gay males reported a significantly higher prevalence of poor body image, frequent dieting, binge eating, or purging than heterosexual males in a population-based survey of Minnesota schools.²⁷ YA college men surveyed in 2008 who identified as gay, unsure, or bisexual reported more clinical eating disorders and disordered eating behaviors compared to their heterosexual peers.²⁸ All sexual minority college students were significantly more likely to report dieting to lose weight compared to their heterosexual peers.²⁸

A survey of adolescents revealed that lesbian or bisexual women were equally likely to have had intercourse with men, but more likely than their heterosexual peers to report a pregnancy (12% versus 5%).²⁷ LGB YA college students were less likely to be involved in a pregnancy in the last 12 months (0.6% lesbians and gays, 4.5% bisexuals, 5.1% heterosexuals), but this was not necessarily planned. 43.9% of heterosexual YAs, 33.5% gays/lesbians, and 66.7% bisexuals said the pregnancy was unintentional.²⁹ Among sexually experienced adolescents, lesbian or bisexual women were also more likely to have engaged in prostitution during the previous year (9.7% versus 1.9%).²⁹ Similar data are not currently available in YAs.

LGB YAs are often overlooked in discussions of violence against women and may therefore not have access to needed resources. Abuse of YAs within the LGB community has been invisible to health care workers, and has historically been unacknowledged by the LGB community as well. (see Chapter 73) College student YAs who identify as LGB report significantly higher lifetime rates of domestic violence (both men and women) compared to their heterosexual peers.²⁹ Rates reported by bisexual YA students are significantly higher (45.6%) compared to both lesbian/gay (35.7%) and heterosexual students (25.6%).²⁴