Biomedical subjects

R C Pillard

Publications and source records attributed to R C Pillard.

At least 19 recordsLinked to original sources

PubMed2000

Familial aspects of male homosexuality.

Research has generally supported the existence of familial-genetic factors for male sexual orientation, but has not shed much light on the specific nature of those influences. Gay men with gay brothers provide the opportunity to examine several hypotheses. Sixty-six men, representing 37 gay male sibling pairs, completed questionnaires assessing behavior on various measures including childhood and adult gender nonconformity, timing of awareness of homosexual feelings, self-acceptance, and the quality of family relationships. Consistent with prior findings using twins, gay brothers were similar in their degree of childhood gender non-conformity, suggesting that this variable may distinguish etiologically (e.g., genetically) heterogeneous subtypes. The large majority of gay men with brothers knew about their own homosexual feelings before they learned about their brothers' homosexual feelings, suggesting that discovery of brothers' homosexuality is not an important cause of male homosexuality.

Adult↗

PubMed1999

A family history study of male sexual orientation using three independent samples.

Available evidence suggests that male homosexuality is both familial and somewhat heritable and that some cases may be caused by an X-linked gene. However, most studies have recruited subjects in a relatively unsystematic manner, typically via advertisements, and hence suffer from the potential methodological flaw of ascertainment bias due to volunteer self-selection. In the present study we assessed the familiality of male homosexuality using two carefully ascertained samples and attempted to replicate findings consistent with X-linkage in three samples. The percentage of siblings of the probands rated as either homosexual or bisexual, with a high degree of certainty, ranged from 7 to 10% for brothers and 3 to 4% for sisters. These estimates are higher than recent comparable population-based estimates of homosexuality, supporting the importance of familial factors for male homosexuality. Estimates of lambda s for male homosexuality ranged from 3.0 to 4.0. None of the samples showed a significantly greater proportion of maternal than paternal homosexual uncles or homosexual male maternal first cousins. Although our results differed significantly with those of some prior studies, they do not exclude the possibility of moderate X-linkage for male sexual orientation.

Adolescent↗

PubMed1998

Human sexual orientation has a heritable component.

We present an overview of behavioral genetics research on homosexual and heterosexual orientation. Family, twin, and adoptee studies indicate that homosexuality and thus heterosexuality run in families. Sibling, twin, and adoptee concordance rates are compatible with the hypothesis that genes account for at least half of the variance in sexual orientation. We note observations of homosexual behavior in animal species, but the analogy to human sexual orientation is unclear. We discuss the reproductive disadvantage of a homosexual orientation and present possible mechanisms that could maintain a balanced polymorphism in human populations.

Animals↗

PubMed1995

A biologic perspective on sexual orientation.

Sexual orientation may be defined as the sustained erotic attraction to members of one's own gender, the opposite gender, or both--homosexual, heterosexual, or bisexual, respectively. Interest in sexual orientation is as old as the science of psychology, yet many fundamental issues remain unresolved. This article reviews research in the development and psychopathology of sexual orientation as well as the results of family and twin studies. Research in genetic linkage, sex hormones, and brain differences also is discussed.

Adolescent↗

PubMed1994

Personality and lipid level differences associated with homosexual and bisexual identity in men.

Self-identified homosexual (n = 30), bisexual (n = 29), and heterosexual (n = 31) men were compared on measures of gender-typical behavior, sex role, ego strength, and lipid levels. Homosexual men differed significantly from the heterosexual men on the gender-typical behavior and feminine sex-role measure (both in adulthood and in childhood), and several trends and significant differences were found on the biochemical measures of lipid levels (especially when 7 obese men were removed from the analyses). As a rule, the bisexual men were different from the heterosexual men on the above measures, but were indistinguishable from the homosexual men. Bisexuals differed from both of the other two groups, however, by scoring lower on the ego strength scale and by reporting themselves to be more often troubled, lonely, and depressed. We caution that the lipid analyses were made on single blood samples and require an extended replication; however, we report the data because of their possible theoretical interest and because they replicate work of 20 years ago.

Adult↗

PubMed1993

Heritable factors influence sexual orientation in women.

Homosexual female probands with monozygotic cotwins, dizygotic cotwins, or adoptive sisters were recruited using homophile publications. Sexual orientation of relatives was assessed either by asking relatives directly, or, when this was impossible, by asking the probands. Of the relatives whose sexual orientation could be confidently rated, 34 (48%) of 71 monozygotic cotwins, six (16%) of 37 dizygotic cotwins, and two (6%) of 35 adoptive sisters were homosexual. Probands also reported 10 (14%) nontwin biologic sisters to be homosexual, although those sisters were not contacted to confirm their orientations. Heritabilities were significant using a wide range of assumptions about both the base rate of homosexuality in the population and ascertainment bias. The likelihood that a monozygotic cotwin would also be homosexual was unrelated to measured characteristics of the proband such as self-reported history of childhood gender nonconformity. Concordant monozygotic twins reported similar levels of childhood gender nonconformity.

Adoption↗

PubMed1993

A factor analysis of the Klein sexual orientation grid in two disparate samples.

Many researchers interested in sexual orientation can be separated into two camps: The "lumpers," who try to reduce sexual classifications to as small a number of categories as possible, and the "splitters," who try to show differences among groups and individuals that make classification schemes increasingly difficult and/or intricate. We report factor analyses of the Klein Grid (a questionnaire with 21 sexual orientation items) to see how many factors emerge in two samples of strikingly different origins. In both samples, the first factor to emerge loaded substantially on all of the Klein Grid's 21 items. This factor accounted for a majority of the variance. In both samples, a second, correlated factor emerged which indexed a separation between most of the items and those having to do with social and/or emotional preferences. In both samples, a third correlated factor also emerged, but this factor differed between the two populations: one refined the social/emotional distinction and the other distinguished ideal behavior from past and current behavior. We conclude on the basis of our analysis that both the lumpers and the splitters are correct.

Bisexuality↗

PubMed1991

A genetic study of male sexual orientation.

Homosexual male probands with monozygotic cotwins, dizygotic cotwins, or adoptive brothers were recruited using homophile publications. Sexual orientation of relatives was assessed either by asking relatives directly, or when this was impossible, asking the probands. Of the relatives whose sexual orientation could be rated, 52% (29/56) of monozygotic cotwins, 22% (12/54) of dizygotic cotwins, and 11% (6/57) of adoptive brothers were homosexual. Heritabilities were substantial under a wide range of assumptions about the population base rate of homosexuality and ascertainment bias. However, the rate of homosexuality among nontwin biological siblings, as reported by probands, 9.2% (13/142), was significantly lower than would be predicted by a simple genetic hypothesis and other published reports. A proband's self-reported history of childhood gender non-conformity did not predict homosexuality in relatives in any of the three subsamples. Thus, childhood gender nonconformity does not appear to be an indicator of genetic loading for homosexuality. Cotwins from concordant monozygotic pairs were very similar for childhood gender nonconformity.

Adoption↗

PubMed1991

Sexual orientation and cognitive abilities.

We asked whether homosexual and heterosexual men and women differ on standard measures of cognitive ability. Subjects were adults recruited for a family study of sexual orientation. They completed the Fy Scale of the California Psychological Inventory, a self-administered measure of psychological "femininity," and were given subtests of the Wechsler Adult Intelligence Scale and the Primary Mental Abilities test which had been previously shown to discriminate between the sexes. We predicted that homosexual subjects would score significantly in the gender-atypical direction on the Fy scale. We also predicted that they would achieve scores on the tests of cognitive abilities significantly in the direction of the other gender. Comparisons were made between homosexual and heterosexual individuals within gender. Also, comparisons were made between heterosexual men and women to see if our results replicate differences typically found between the genders. As predicted, both homosexual men and women were strongly gender-atypical on the Fy scale relative to their heterosexual counterparts. However, neither differed from heterosexuals on any of the measures of cognitive abilities. Heterosexual men did better than women on the Primary Mental Abilities spatial relations test. We conclude that sexual orientation is not related to specific cognitive abilities.

Cognition↗

PubMed1986

Evidence of familial nature of male homosexuality.

We recruited 51 predominantly homosexual and 50 predominantly heterosexual men as index subjects for a family study of sexual orientation. The sexual orientation of siblings (115 sisters and 123 brothers) was ascertained in two ways: via interview with the index subjects and via interview of and/or mailed questionnaire to the siblings themselves. Index subjects' knowledge of the sexual orientation of their siblings was, for the most part, quite accurate. Moreover, heterosexual index men had about as many homosexual brothers as would be predicted given national prevalence figures for homosexuality, but homosexual index men had about four times as many homosexual brothers, although in both cases most brothers were heterosexual. There was no significant difference between the index groups in number of homosexual sisters. We conclude that there is a significant familial component to male homosexuality.

Educational Status↗

PubMed1982

A family study of sexual orientation.

Unmarried men aged 25--35 were recruited through newspaper and radio advertisements for a family study of sexual orientation. Fifty predominantly homosexual and 50 predominantly heterosexual men comprised the index subjects. The test, questionnaire, and interview battery is described. Subjects were asked about the sexual orientations of their relatives. The homosexual index men report a significant excess of homosexual brothers and more distant male relatives but not of homosexual sisters or female relatives. Moreover, the percentage of homosexual brothers increases with the Kinsey rating of the index subjects. Overall, about 25% of brothers of homosexual men are reported also to be homosexual.

Adult↗

PubMed1981

Is homosexuality familial? A review, some data, and a suggestion.

This report summarizes evidence that sexual orientation is familial. Family studies report that homosexual subjects have more homosexual siblings than do heterosexual subjects and more than would be expected given population frequencies. Twin studies find in general a higher concordance in sexual orientation among monozygotic than among dizygotic twins. Evidence for associated psychopathology in homosexual subjects or their relatives is inconclusive. Possible sources of bias in these reports are discussed and a suggestion is offered that family studies should be undertaken in which the sexual orientation of relatives would be directly ascertained by interview.

Family↗

PubMed1974