The neurodevelopment of human sexual orientation

Genetic and Environmental Influences on Sexual Orientation: Moderation by Childhood Gender Nonconformity and Early-Life Adversity

Existing evidence indicates genetic and non-genetic influences on sexual orientation; however, the possibility of gene-environment interplay has not been previously formally tested despite theories indicating this. Using a Finnish twin cohort, this study investigated whether childhood gender nonconformity and early-life adversities independently moderated individual differences in sexual orientation and childhood gender nonconformity, the relationship between them, and the etiological bases of the proposed moderation effects. Sexual orientation, childhood gender nonconformity, and early-life adversities were assessed using standard questionnaires. Structural equation twin model fitting was carried out using OpenMx. Childhood gender nonconformity was significantly associated with reduced phenotypic variance in sexual orientation (β =  - 0.14, 95% CI - 0.27, - 0.01). A breakdown of the underlying influences of this moderation effect showed that this was mostly due to moderation of individual-specific environmental influences which significantly decreased as childhood gender nonconformity increased (βE =  - 0.38; 95% CI - 0.52, - 0.001) while additive genetic influences were not significantly moderated (βA = 0.05; 95% CI - 0.30, 0.27). We also observed that the relationship between sexual orientation and childhood gender nonconformity was stronger at higher levels of childhood gender nonconformity (β = 0.10, 95% CI 0.05, 0.14); however, significance of the underlying genetic and environmental influences on this relationship could not be established in this sample. The findings indicate that beyond a correlation of their genetic and individual-specific environmental influences, childhood gender nonconformity is further significantly associated with reduced individual-specific influences on sexual orientation.

Sex and gender correlates of sexually polymorphic cognition

BACKGROUND

Sexually polymorphic cognition (SPC) results from the interaction between biological (birth-assigned sex (BAS), sex hormones) and socio-cultural (gender identity, gender roles, sexual orientation) factors. The literature remains quite mixed regarding the magnitude of the effects of these variables. This project used a battery of classic cognitive tests designed to assess the influence of sex hormones on cognitive performance. At the same time, we aimed to assess the inter-related and respective effects that BAS, sex hormones, and gender-related factors have on SPC.

METHODS

We recruited 222 adults who completed eight cognitive tasks that assessed a variety of cognitive domains during a 150-min session. Subgroups were separated based on gender identity and sexual orientation and recruited as follows: cisgender heterosexual men (n = 46), cisgender non-heterosexual men (n = 36), cisgender heterosexual women (n = 36), cisgender non-heterosexual women (n = 38), gender diverse (n = 66). Saliva samples were collected before, during, and after the test to assess testosterone, estradiol, progesterone, cortisol, and dehydroepiandrosterone. Psychosocial variables were derived from self-report questionnaires.

RESULTS

Cognitive performance reflects sex and gender differences that are partially consistent with the literature. Interestingly, biological factors seem to better explain differences in male-typed cognitive tasks (i.e., spatial), while psychosocial factors seem to better explain differences in female-typed cognitive tasks (i.e., verbal).

CONCLUSION

Our results establish a better comprehension of SPC over and above the effects of BAS as a binary variable. We highlight the importance of treating sex as a biological factor and gender as a socio-cultural factor together since they collectively influence SPC.

Alternative Sexual Orientation in Humans: What Is Known and What Needs to Be Known Further

Since the 20th century, multiple studies have linked the variations in human sexual orientation, from heterosexuality to bisexuality or homosexuality, to a wide range of biological factors. However, a clear mechanism that leads to the development of these variations has not been established yet. This review consolidates various comprehensive studies on the possible biological factors in the fields of genetics, epigenetics, uterine environment, hormones, neuroanatomy, and neurobiology that lead to these variations. One intriguing question that 'homosexuality phenotype' faces is its ability to avoid elimination by Darwinian selection. This review tries to explain why natural selection is not eliminating the genetic factors associated with homosexuality even at the cost of the evolutionary fitness of homosexual individuals. Studies supporting certain strong candidates for alternative sexual orientation (ASO) are highlighted, which can become new research avenues for investigators in this field. Further, a novel speculation is proposed that might be contributing to the development of variation in human sexuality.

Continuum of Symptoms in Polycystic Ovary Syndrome (PCOS): Links with Sexual Behavior and Unrestricted Sociosexuality

Symptoms of polycystic ovary syndrome (PCOS) exist on a continuum, are associated with hyperandrogenism, and have fertility implications. The present study investigated the relationship between PCOS symptoms and sociosexuality in young women with a continuum of symptoms ranging from none to clinical levels. Given that unrestricted sociosexuality, or one's orientation toward uncommitted sexual activity, is associated with hyperandrogenism, we hypothesized that women experiencing more symptoms of PCOS, and a greater likelihood of androgen excess, would have a more unrestricted sociosexual orientation. Women completed questionnaires about PCOS symptoms, sociosexuality, and sexuality. Unrestricted sociosexuality, unrestricted desire, romantic interest in women, and masturbation frequency were all positively associated with PCOS symptoms (including male pattern hair growth). The sexuality scores were also higher in women who scored above (versus below) the cutoff on a self-report PCOS screening questionnaire. In addition, attraction to women was higher in participants reporting a past diagnosis of PCOS. The findings are in line with theories that androgens play a role in sociosexuality and sexual orientation. Future research should examine sociocultural explanations, and whether the continuum of PCOS symptoms (e.g., hirsutism) is a useful model for studying the effects of androgen exposure, hyperandrogenism, or androgen responsiveness on women's behavior.

Cross-sex shifts in two brain imaging phenotypes and their relation to polygenic scores for same-sex sexual behavior: A study of 18,645 individuals from the UK Biobank

Genetic and hormonal factors have been suggested to influence human sexual orientation. Previous studied proposed brain differences related to sexual orientation and that these follow cross-sex shifted patterns. However, the neurobiological correlates of sexual orientation and how genetic factors relate to brain structural variation remains largely unexplored. Using the largest neuroimaging-genetics dataset available on same-sex sexual behavior (SSB) (n = 18,645), we employed a data-driven multivariate classification algorithm (PLS) on magnetic resonance imaging data from two imaging modalities to extract brain covariance patterns related to sex. Through analyses of latent variables, we tested for SSB-related cross-sex shifts in such patterns. Using genotype data, polygenic scores reflecting the genetic predisposition for SSB were computed and tested for associations with neuroimaging outcomes. Patterns important for classifying between males and females were less pronounced in non-heterosexuals. Predominantly in non-heterosexual females, multivariate brain patterns as represented by latent variables were shifted toward the opposite sex. Complementary univariate analyses revealed region specific SSB-related differences in both males and females. Polygenic scores for SSB were associated with volume of lateral occipital and temporo-occipital cortices. The present large-scale study demonstrates multivariate neuroanatomical correlates of SSB, and tentatively suggests that genetic factors related to SSB may contribute to structural variation in certain brain structures. These findings support a neurobiological basis to the differences in human sexuality.

Male Ejaculatory Endophenotypes: Revealing Internal Inconsistencies of the Concept in Heterosexual Copulating Rats

Distinct manifestations of sexual behavior are conceived as separate phenotypes. Each sexual phenotype is assumed to be associated with a characteristic brain. These notions have justified the phenotyping of heterosexual copulator males based upon their ejaculation's latencies (EL) or frequencies (i.e., cumulative ejaculation number; EN). For instance, men and male rats showing premature, normal or retarded ejaculation are assumed to be distinctive endophenotypes. This concept, nonetheless, contradicts past and recent evidence that supports that sexual behavior is highly variable within each sex, and that the brain sexual functional morphology represents an intricate sexual phenotypic mosaic. Hence, for ejaculatory male endophenotypes to be considered as a valid biological concept, it must show internal consistency at various levels of organization (including genetic architectures), after being challenged by intrinsic and/or extrinsic factors. We then judged the internal consistency of the presumed ejaculatory endophenotypes by assessing whether copulatory behavior and the expression of copulation relevant genes and brain limbic structures are specific to each of the presumed EL- or EN-ejaculatory endophenotypes. To do this, copulating male rats were first phenotyped in groups consistently displaying short, average or long ejaculation latencies or very high, high, average, low or very low EN, based in their copulatory performance. Then, the internal consistency of the presumed EL- or EN-endophenotypes was tested by introducing as covariates of phenotyping other copulatory parameters (e.g., number of intromissions) in addition to EL or EN, or by analyzing the expression levels of genes encoding for estrogen receptor alpha, progesterone receptor, androgen receptor, aromatase, DNA methyl-transferase 3a and DNA methyl-transferase 1 in the amygdala, medial preoptic area, ventromedial hypothalamus and olfactory bulb. We found that even though there were group-level differences in all the variables that were studied, these differences did not add-up to create the presumed EL- or EN-ejaculatory endophenotypes. In fact, the extensive overlapping of copulatory parameters and expression levels of copulation relevant genes in limbic structures across EL- or EN-phenotyped copulating male rats, is not consistent with the hypothesis that distinct ejaculatory endophenotypes exist and that they are associated with specific brain characteristics.

Sexual Orientation and Cognitive Ability: A Multivariate Meta-Analytic Follow-Up

A cross-sex shift model of human sexual orientation differences predicts that homosexual men should perform or score in the direction of heterosexual women, and homosexual women in the direction of heterosexual men, in behavioral domains such as cognition and personality. In order to test whether homosexual men and women's cognitive performance was closer to that of heterosexual men or that of heterosexual women (i.e., sex-atypical for their sex and closer to that of the opposite-sex), we conducted a multivariate meta-analysis based on data from our previous meta-analysis (Xu, Norton, & Rahman, 2017). A subset of this data was used and comprised 30 articles (and 2 unpublished datasets) and 244,434 participants. The multivariate meta-analysis revealed that homosexual men were sex-atypical in mental rotation (Hedges' g = -0.36) and the water level test (Hedges' g = -0.55). In mental rotation, homosexual men were in-between heterosexual men and women. There was no significant group difference on spatial location memory. Homosexual men were also sex-atypical on male-favoring spatial-related tasks (Hedges' g = -0.54), and female-favoring spatial-related tasks (Hedges' g = 0.38). Homosexual women tended to be sex-typical (similar to heterosexual women). There were no significant group differences on male-favoring "other" tasks or female-favoring verbal-related tasks. Heterosexual men and women differed significantly on female-favoring "other" tasks. These results support the cross-sex shift hypothesis which predicts that homosexual men perform in the direction of heterosexual women in sex differentiated cognitive domains. However, the type of task and cognitive domain tested is critical.

Child sexual offenders show prenatal and epigenetic alterations of the androgen system

Child sexual offending (CSO) places a serious burden on society and medicine and pedophilia (P) is considered a major risk factor for CSO. The androgen system is closely linked to sexual development and behavior. This study assessed markers of prenatal brain androgenization, genetic parameters of androgen receptor function, epigenetic regulation, and peripheral hormones in a 2 × 2 factorial design comprising the factors Offense (yes/no) and Pedophilia (yes/no) in analyzing blood samples from 194 subjects (57 P+CSO, 45 P-CSO, 20 CSO-P, and 72 controls) matched for age and intelligence. Subjects also received a comprehensive clinical screening. Independent of their sexual preference, child sexual offenders showed signs of elevated prenatal androgen exposure compared with non-offending pedophiles and controls. The methylation status of the androgen receptor gene was also higher in child sexual offenders, indicating lower functionality of the testosterone system, accompanied by lower peripheral testosterone levels. In addition, there was an interaction effect on methylation levels between offense status and androgen receptor functionality. Notably, markers of prenatal androgenization and the methylation status of the androgen receptor gene were correlated with the total number of sexual offenses committed. This study demonstrates alterations of the androgen system on a prenatal, epigenetic, and endocrine level. None of the major findings was specific for pedophilia, but they were for CSO. The findings support theories of testosterone-linked abnormalities in early brain development in delinquent behavior and suggest possible interactions of testosterone receptor gene methylation and plasma testosterone with environmental factors.

Finger Length Ratios of Identical Twins with Discordant Sexual Orientations

A proposed marker of prenatal androgen exposure is the ratio of the index finger to ring finger (2D:4D). Within each sex, this ratio may be lower for those who were exposed to higher levels of androgens and become attracted to women, as compared to those who were exposed to lower levels of androgens and become attracted to men. We examined these patterns in identical twins with discordant sexual orientations. Because these twins are genetically identical, differences in prenatal androgen exposure, as reflected in their different finger length ratios, might contribute to their discordance. For 18 female twin pairs, non-straight (bisexual or lesbian) twins had significantly lower, or more masculinized, 2D:4D ratios than their straight co-twins, but only in the left hand. For 14 male pairs, non-straight twins had, contrary to our prediction, more masculinized finger length ratios than straight co-twins, but this difference was not significant. A reanalysis of present and previous data (Hall & Love, 2003; Hiraishi, Sasaki, Shikishima, & Ando, 2012) suggested that these patterns were robust. Furthermore, males had more masculinized 2D:4D ratios than females. This sex difference did not vary by sexual orientation.

Biological origins of sexual orientation and gender identity: Impact on health

Gynecologic Oncologists are sometimes consulted to care for patients who present with diverse gender identities or sexual orientations. Clinicians can create more helpful relationships with their patients if they understand the etiologies of these diverse expressions of sexual humanity. Multidisciplinary evidence reveals that a sexually dimorphic spectrum of somatic and neurologic anatomy, traits and abilities, including sexual orientation and gender identity, are conferred together during the first half of pregnancy due to genetics, epigenetics and the diversity of timing and function of sex chromosomes, sex-determining protein secretion, gonadal hormone secretion, receptor levels, adrenal function, maternally ingested dietary hormones, fetal health, and many other factors. Multiple layers of evidence confirm that sexual orientation and gender identity are as biological, innate and immutable as the other traits conferred during that critical time in gestation. Negative social responses to diverse orientations or gender identities have caused marginalization of these individuals with resultant alienation from medical care, reduced self-care and reduced access to medical care. The increased risks for many diseases, including gynecologic cancers are reviewed. Gynecologic Oncologists can potentially create more effective healthcare relationships with their patients if they have this information.

Cortical brain structure and sexual orientation in adult females with bipolar disorder or attention deficit hyperactivity disorder

BACKGROUND

Nonheterosexual individuals have higher risk of psychiatric morbidity. Together with growing evidence for sexual orientation-related brain differences, this raises the concern that sexual orientation may be an important factor to control for in neuroimaging studies of neuropsychiatric disorders.

METHODS

We studied sexual orientation in adult psychiatric patients with bipolar disorder (BD) or ADHD in a large clinical cohort (N = 154). We compared cortical brain structure in exclusively heterosexual women (HEW, n = 29) with that of nonexclusively heterosexual women (nHEW, n = 37) using surface-based reconstruction techniques provided by FreeSurfer.

RESULTS

The prevalence of nonheterosexual sexual orientation was tentatively higher than reported in general population samples. Consistent with previously reported cross-sex shifted brain patterns among homosexual individuals, nHEW patients showed significantly larger cortical volumes than HEW in medial occipital brain regions.

CONCLUSION

We found evidence for a sex-reversed difference in cortical volume among nonheterosexual female patients, which provides insights into the neurobiology of sexual orientation, and may provide the first clues toward a better neurobiological understanding of the association between sexual orientation and mental health. We also suggest that sexual orientation is an important factor to consider in future neuroimaging studies of populations with certain mental health disorders.

The Puzzle of Male Chronophilias

In this article, I return to the idea that pedophilia, a sexual interest in prepubescent children, can be considered a sexual orientation for age, in conjunction with the much more widely acknowledged and discussed sexual orientation for gender. Here, I broaden the scope to consider other chronophilias, referring to paraphilias for age/maturity categories other than young sexually mature adults. The puzzle of chronophilias includes questions about etiology and course, how chronophilias are related to each other, and what they can tell us about how human (male) sexuality is organized. In this article, I briefly review research on nepiophilia (infant/toddlers), pedophilia (prepubescent children), hebephilia (pubescent children), ephebophilia (postpubescent, sexually maturing adolescents), teleiophilia (young sexually mature adults, typically 20s and 30s), mesophilia (middle-aged adults, typically 40s and 50s), and gerontophilia (elderly adults, typically 60s and older) in the context of a multidimensional sexual orientations framework. Relevant research, limitations, and testable hypotheses for future work are identified.

On the Relationship Between Domain-Specific Creative Achievement and Sexual Orientation in Swedish Twins

Despite the commonly held belief that homosexual males and females are more creative compared to heterosexuals, empirical studies on homosexuality and its relationship to creativity have been sparse, often with questionable methodology and very small sample sizes, reporting mixed findings. No study till date has explored the associations described above in a large population-based and genetically informative sample. Here, we examined such potential associations between sexual orientation and creative achievement in several different domains (music, writing, dance, visual arts, science, invention, and theater) using a large cohort of 4494 Swedish twins (of which 7.5 % were not exclusively heterosexual). Data were analyzed for the sexes separately as well as pooled. Results showed significant associations between sexual orientation and two of the creative domains-theater and writing-with non-heterosexuals being more creative in these domains. In all other domains, no significant differences were found between the non-heterosexual and heterosexual groups. Findings from co-twin control analyses suggested that the significant associations may not be causal in nature (i.e., homosexual orientation leads to higher creativity) but due to shared liability. However, we lacked power to differentiate between shared genetic and shared environmental influences. Results and potential implications are discussed critically.

Developmental and Functional Effects of Steroid Hormones on the Neuroendocrine Axis and Spinal Cord

This review highlights the principal effects of steroid hormones at central and peripheral levels in the neuroendocrine axis. The data discussed highlight the principal role of oestrogens and testosterone in hormonal programming in relation to sexual orientation, reproductive and metabolic programming, and the neuroendocrine mechanism involved in the development of polycystic ovary syndrome phenotype. Moreover, consistent with the wide range of processes in which steroid hormones take part, we discuss the protective effects of progesterone on neurodegenerative disease and the signalling mechanism involved in the genesis of oestrogen-induced pituitary prolactinomas.

A neural circuit encoding sexual preference in humans

Sexual preference determines mate choice for reproduction and hence guarantees conservation of species in mammals. Despite this fundamental role in human behavior, current knowledge on its target-specific neurofunctional substrate is based on lesion studies and therefore limited. We used meta-analytic remodeling of neuroimaging data from 364 human subjects with diverse sexual interests during sexual stimulation to quantify neural regions associated with sexual preference manipulations. We found that sexual preference is encoded by four phylogenetically old, subcortical brain structures. More specifically, sexual preference is controlled by the anterior and preoptic area of the hypothalamus, the anterior and mediodorsal thalamus, the septal area, and the perirhinal parahippocampus including the dentate gyrus. In contrast, sexual non-preference is regulated by the substantia innominata. We anticipate the identification of a core neural circuit for sexual preferences to be a starting point for further sophisticated investigations into the neural principles of sexual behavior and particularly of its aberrations.

Scrutinizing Immutability: Research on Sexual Orientation and U.S. Legal Advocacy for Sexual Minorities

We review scientific research and legal authorities to argue that the immutability of sexual orientation should no longer be invoked as a foundation for the rights of individuals with same-sex attractions and relationships (i.e., sexual minorities). On the basis of scientific research as well as U.S. legal rulings regarding lesbian, gay, and bisexual (LGB) rights, we make three claims: First, arguments based on the immutability of sexual orientation are unscientific, given what we now know from longitudinal, population-based studies of naturally occurring changes in the same-sex attractions of some individuals over time. Second, arguments based on the immutability of sexual orientation are unnecessary, in light of U.S. legal decisions in which courts have used grounds other than immutability to protect the rights of sexual minorities. Third, arguments about the immutability of sexual orientation are unjust, because they imply that same-sex attractions are inferior to other-sex attractions, and because they privilege sexual minorities who experience their sexuality as fixed over those who experience their sexuality as fluid. We conclude that the legal rights of individuals with same-sex attractions and relationships should not be framed as if they depend on a certain pattern of scientific findings regarding sexual orientation.

Putative Androgen Exposure and Sexual Orientation: Cross-Cultural Evidence Suggesting a Modified Neurohormonal Theory

INTRODUCTION

According to neurohormonal theory, prenatal androgens are key determinants of sexual orientation. As a reputed marker for prenatal androgens, the 2D:4D finger length ratio has been used in more than a dozen studies to test the hypothesis that prenatal androgens influence sexual orientation. Findings have been very inconsistent.

AIM

The present study sought to retest the hypothesis that 2D:4D and sexual orientation are related is a manner consistent with neurohormonal theory.

METHODS

A 2D:4D measure (of the right hand) along with four additional somatic markers of androgen exposure (height, physical strength, muscularity, and athletic ability) with samples of college students in Malaysia (N = 2,058) and the United States (N = 2,511). The five androgen measures were factor analyzed, resulting in a two-factor solution: Factor 1 consisted of strength, muscularity, and athletic ability (the muscular coordination factor), and Factor 2 was comprised of the r2D:4D and adult height (the bone growth factor).

MAIN OUTCOME MEASURES

Sexual orientation was measured by asking each respondent the extent to which they were sexually attracted to males and the extent to which they were sexually attracted to females, both on 11-point scales.

RESULTS

When the countries and sexes were analyzed separately, neither the r2D:4D measure nor Factor 2 correlated with sexual orientation to significant degrees. Instead, it was the muscular coordination factor that correlated the best. Support was found for the hypothesis that prenatal androgens influence sexual orientation, but the nature of these influences was more complex than neurohormonal theory predicted.

CONCLUSION

A modified theory is needed and presented to accommodate the results from this study.

High Rates of Same-Sex Attraction/Gender Nonconformity in the Offspring of Mothers with Thyroid Dysfunction During Pregnancy: Proposal of Prenatal Thyroid Model

Both youngsters and adults with same-sex attraction are at greater risk for negative health outcomes. Despite mounting efforts to determine the biological background, a satisfactory conclusion has not been reached and there is a need to explore alternate factors like functioning of thyroid system during pregnancy. A retrospective chart review was undertaken of 790 eligible children and adolescents who had been admitted to child psychiatry between 2005 and 2013. This population consisted of 520 (65%) males and 270 (35%) females, aged 8 to 17 years. Fifteen mothers (1.8%) were found to have a history of thyroid dysfunction during pregnancy. Sixteen youngsters (2%) had a history of same-sex attraction. Twelve overlapping cases with both same-sex attraction and maternal thyroid dysfunction during pregnancy were identified, which was extremely significant (P<0.0001, by Fisher’s exact test). The association was also significant for each sex (P<0.0001, by Fisher’s exact test). There is evidence that thyroid gland plays a crucial and decisive role in determining sexual orientation in people. Maternal thyroid dysfunctions during pregnancy may result in homosexual orientation in the offspring.

Implicaciones bioéticas derivadas del acceso de las parejas del mismo sexo a las técnologías provenientes de la biomedicina y la biotecnología para la conformación de familias homoparentales

En este artículo se realiza una reflexión y una revisión, desde el ámbito de las ciencias básicas y del bioderecho, sobre los aspectos biológicos y genéticos de la homosexualidad, y sobre el impacto que tiene en la familia el acceso a las técnicas de reproducción asistida por parte de las parejas del mismo sexo. Lo anterior nos lleva al desarrollo de conceptos como la “violencia prenatal”, el derecho de los niños a crecer en el seno de una familia con una imagen paterna y materna, al igual que las implicaciones que estos conceptos tienen a la luz del orden jurídico colombiano.

The relationship between temperament and sexual orientation

BACKGROUND

The relationship between temperament and sexual orientation has been poorly characterized. We have used the Affective and Emotional Composite Temperament (AFECT) model to evaluate this association in a large population sample.

METHODS

Data from 16,571 subjects between 21 and 45 years old (mean age=29.1±6.3 yrs, 69.4% females) was collected anonymously through Internet in Brazil.

RESULTS

Regarding affective temperaments, male cyclothymics and dysphorics had the lowest percentage of people with heterosexual orientation and the highest percentages of people with bisexual and homosexual orientations. The opposite profile was observed in hyperthymic and euthymic types. Among females, the volatile, cyclothymic, apathetic, disinhibited and euphoric types were less often observed in people with "pure" heterosexual orientation and more often in people with bisexual orientation. In men only, homosexuality was more common among the depressive, cyclothymic and dyphorics temperaments. Emotional trait analysis showed that heterosexual subjects differed statistically from all other groups by having higher scores of coping and stability and lower scores of sensitivity and desire. Overall, the effect sizes were small to moderate, with the largest differences between "pure" heterosexuals and people with bisexual orientation, particularly in women. Subjects with heterosexual orientation who have had homosexual experience and those with homosexual orientation presented intermediate scores.

LIMITATIONS

Cross-sectional design, lack of potentially important covariates (e.g., maltreatment) and data collected by Internet only.

CONCLUSION

Externalized and unstable traits were associated mainly with bisexuality. The group of heterosexuals with homosexual fantasies or experiences offers a new approach for the study of sexual orientation.

Human homosexuality: a paradigmatic arena for sexually antagonistic selection?

Sexual conflict likely plays a crucial role in the origin and maintenance of homosexuality in our species. Although environmental factors are known to affect human homosexual (HS) preference, sibling concordances and population patterns related to HS indicate that genetic components are also influencing this trait in humans. We argue that multilocus, partially X-linked genetic factors undergoing sexually antagonistic selection that promote maternal female fecundity at the cost of occasional male offspring homosexuality are the best candidates capable of explaining the frequency, familial clustering, and pedigree asymmetries observed in HS male proband families. This establishes male HS as a paradigmatic example of sexual conflict in human biology. HS in females, on the other hand, is currently a more elusive phenomenon from both the empirical and theoretical standpoints because of its fluidity and marked environmental influence. Genetic and epigenetic mechanisms, the latter involving sexually antagonistic components, have been hypothesized for the propagation and maintenance of female HS in the population. However, further data are needed to truly clarify the evolutionary dynamics of this trait.

Indian womanhood: some psychological concepts

Indian womanhood today is at crossroads. The present paper discusses the status of Indian womanhood and its psychological underpinnings. It discusses how Indian women have suffered at the hands of their families and society leaving no path but to succumb to psychiatric illness. The role of mental health professionals and family members in supporting and promoting growth and development of the Indian woman is outlined.

[Beyond the transparent body: a consideration of the methods and strategies for examining the homosexual subject]

The aims of the study are to look at methods and strategies used for analyzing people and classifying them as homosexual and to discuss how certain mechanisms which have been established have made it possible to look at their bodies and arrive at conclusions with regard to such persons. We analyze articles from Science Direct, using a Foucaultian approach. We observe the operation of two technologies: medical body imaging techniques and examinations. These techniques transform the individuals into parts of a strategic device which can be used to build up knowledge, produce files and data, and classify the subjects. The development of this research makes it possible for us to identify certain relationships between homosexuality, the production of scientific knowledge, prejudice, politics and health.

Sexual orientation related differences in cortical thickness in male individuals

Previous neuroimaging studies demonstrated sex and also sexual orientation related structural and functional differences in the human brain. Genetic information and effects of sex hormones are assumed to contribute to the male/female differentiation of the brain, and similar effects could play a role in processes influencing human's sexual orientation. However, questions about the origin and development of a person's sexual orientation remain unanswered, and research on sexual orientation related neurobiological characteristics is still very limited. To contribute to a better understanding of the neurobiology of sexual orientation, we used magnetic resonance imaging (MRI) in order to compare regional cortical thickness (Cth) and subcortical volumes of homosexual men (hoM), heterosexual men (heM) and heterosexual women (heW). hoM (and heW) had thinner cortices primarily in visual areas and smaller thalamus volumes than heM, in which hoM and heW did not differ. Our results support previous studies, which suggest cerebral differences between hoM and heM in regions, where sex differences have been reported, which are frequently proposed to underlie biological mechanisms. Thus, our results contribute to a better understanding of the neurobiology of sexual orientation.

Psychological and physical health of mostly heterosexuals: a systematic review

We reviewed whether mostly heterosexuals, a sexual orientation group characterized by a small amount of same-sex sexuality, differ from heterosexuals and bisexuals on a variety of mental and physical health outcomes (e.g., internalizing problems, body dissatisfaction and disordered eating, obesity, sexual/reproductive health, physical health), health risk behaviors (e.g., substance use, sexual risk taking), and risk and protective factors (e.g., victimization, stressful/risky environment, socioeconomic status, personal and social relationships, gender nonconformity). A narrative and quantitative literature review was conducted of 60 papers covering 22 samples from five Western countries. Individual, mean, and median effect sizes (Cohen ds) were calculated whenever possible. Mostly heterosexuals reported higher levels of risk in most reviewed outcomes compared to heterosexuals (unweighted mean effect sizes ranged from 0.20 to 0.50) but typically somewhat lower than bisexuals (unweighted mean effect sizes ranged from -0.10 to -0.30). Various risk factors frequently reduced, but rarely eliminated, health disparities between mostly heterosexuals and heterosexuals. Findings are discussed through the lens of three potential explanations of elevated health risks among nonheterosexuals: minority stress, nonheterosexual lifestyles, and common causes. Because data on many outcomes were scarce or missing, particularly for men and in comparison with bisexuals, further research is needed.

The gender you are and the gender you like: sexual preference and empathic neural responses

BACKGROUND

Empathy relates to the ability to share the emotions and understand the intentions and emotions of the other. Although it has been suggested that women have superior empathic abilities as compared to men, it is unknown whether it is the gender or the sexual preference of the individual that affects empathy. Given that sexual attraction has been reported to affect social behavior, the present study explored the possibility that sexual orientation affects behavioral measures of empathy as well as empathy related activations.

METHODS

Fifty two heterosexual and homosexual women and men were scanned while performing an emotional judgment task involving emotional understanding of a protagonist.

RESULTS

The behavioral and neuroimaging results indicate that empathy is related to the gender as well as the sexual preference of the participant. Individuals sexually attracted to men (heterosexual women and homosexual men) showed greater empathy than subjects attracted to women (heterosexual men and homosexual women). Furthermore, brain imaging data reveal that regions within the temporo-parietal junction (TPJ), showed sensitivity to the sexual orientation of the individual, such that it was activated more in subjects attracted to men than in subjects attracted to women while evaluating the emotional state of the other. Moreover, the activation in the TPJ was found to be correlated with the degree to which subjects were empathizing.

CONCLUSIONS

These results suggest that individual differences in empathy are related to the gender as well as the sexual orientation of the subject.

Loneliness of homosexual male students: parental bonding attitude as a moderating factor

The purpose of this paper was to examine the relationships of homosexual male students at the senior high school level and their loneliness using parental bonding attitude as a moderating factor. An amount of 127 homosexual male senior high school students in Taiwan is studied. The Pearson correlation analysis and the hierarchical regression analysis are adapted to examine two proposed hypotheses. Based on the results, homosexual male senior high school students in both hyper-masculine and feminine gender roles are found to feel loneliness, but levels of loneliness of those who possess hyper-masculine gender role are relatively lower than those in a feminine role. In addition, the levels of loneliness of homosexual male senior high school students could be negatively affected by parental bonding attitudes (Care). Recommendations and suggestions for parents as well as teachers of homosexual senior high school male students and future studies are underscored at the end of this article.

Minor physical anomalies in patients with schizophrenia in a Chinese population

Studies have shown that minor physical anomalies (MPAs) may be associated with schizophrenia. However, it remains unclear whether any items of MPAs are more associated with schizophrenia than the others. We aimed to examine which specific MPAs are more associated with schizophrenia than others. A total of 154 patients with schizophrenia and 152 healthy controls were assessed using candidate MPAs items along with items from the Waldrop scale. Significant differences were found between the patients and controls in inner canthal distance, epicanthus, adherent ear lobe, cuspidal ear and length difference from section index to ring finger (2D:4D length difference) as well as gap between the first and the second toes. These six items were selected by the logistic regression model, which correctly classified 89.0% of patients with schizophrenia (sensitivity) and 96.7% of healthy controls (specificity). The overall classification success rate was 92.8%. MPAs are associated with neurodevelopment, especially 2D:4D associated with cerebral lateralisation. Hence, our present findings support that it is necessary to evaluate MPAs beyond the Waldrop scale, as some item, such as 2D:4D length difference may reflect the more detailed aberrant neurodevelopment of schizophrenia.

Do shared etiological factors contribute to the relationship between sexual orientation and depression?

BACKGROUND

Gays, lesbians and bisexuals (i.e. non-heterosexuals) have been found to be at much greater risk for many psychiatric symptoms and disorders, including depression. This may be due in part to prejudice and discrimination experienced by non-heterosexuals, but studies controlling for minority stress, or performed in very socially liberal countries, suggest that other mechanisms must also play a role. Here we test the viability of common cause (shared genetic or environmental etiology) explanations of elevated depression rates in non-heterosexuals.

METHOD

A community-based sample of adult twins (n=9884 individuals) completed surveys investigating the genetics of psychiatric disorder, and were also asked about their sexual orientation. Large subsets of the sample were asked about adverse childhood experiences such as sexual abuse, physical abuse and risky family environment, and also about number of older brothers, paternal and maternal age, and number of close friends. Data were analyzed using the classical twin design.

RESULTS

Non-heterosexual males and females had higher rates of lifetime depression than their heterosexual counterparts. Genetic factors accounted for 31% and 44% of variation in sexual orientation and depression respectively. Bivariate analysis revealed that genetic factors accounted for a majority (60%) of the correlation between sexual orientation and depression. In addition, childhood sexual abuse and risky family environment were significant predictors of both sexual orientation and depression, further contributing to their correlation.

CONCLUSIONS

Non-heterosexual men and women had elevated rates of lifetime depression, partly due to shared etiological factors, although causality cannot be definitively resolved.

Considering the role of conditioning in sexual orientation

The effects of learning on sexual orientation are rarely addressed in the literature. At the very least, such processes provide a means of elaborating upon orientation predispositions. Some aspects of our mates may inherently elicit a sexual response, but other attributes do so only after sexual experience with them. Animal research shows robust, direct effects of conditioning processes on partner preference with a few studies showing plasticity in preference for sex of partner. Descriptive research in humans suggests effects of experience on partner preference and, although experimental demonstrations of human sexual conditioning are neither numerous nor robust, sexual arousal is conditionable in women and men. With modern developments in learning theory (e.g., expectancy learning and evaluative conditioning), it seems appropriate to renew the investigation of contributions and limitations of conditioning processes to explaining how cues acquire erotic value and to attempt some integration between the sexual conditioning literature and research on sexual orientation or more generally sexual partner preference.

Genetic and environmental influences on female sexual orientation, childhood gender typicality and adult gender identity

Background

Human sexual orientation is influenced by genetic and non-shared environmental factors as are two important psychological correlates – childhood gender typicality (CGT) and adult gender identity (AGI). However, researchers have been unable to resolve the genetic and non-genetic components that contribute to the covariation between these traits, particularly in women.

Methodology/Principal Findings

Here we performed a multivariate genetic analysis in a large sample of British female twins (N = 4,426) who completed a questionnaire assessing sexual attraction, CGT and AGI. Univariate genetic models indicated modest genetic influences on sexual attraction (25%), AGI (11%) and CGT (31%). For the multivariate analyses, a common pathway model best fitted the data.

Conclusions/Significance

This indicated that a single latent variable influenced by a genetic component and common non-shared environmental component explained the association between the three traits but there was substantial measurement error. These findings highlight common developmental factors affecting differences in sexual orientation.

The development of male-oriented behavior in rams

The sheep offers a unique mammalian model in which to study paradoxical same-sex sexual partner preferences. Variations in sexual partner preferences occur spontaneously with as many as 8% of rams in a population exhibiting a sexual preference for other rams (male-oriented). The current review presents an overview and update of the male-oriented ram model and discusses several theories that have been invoked to explain same-sex preferences in this species. Although our understanding of the biological determinants and underlying neural substrates of sexual attraction and mate selection are far from complete, compelling evidence is discussed that supports the idea that neural substrates regulating sexual partner preferences are organized during prenatal development. The challenge for future research will be to construct an integrated picture of how hormones, genes, and experience shape sexual partner preference.

Sexual orientation and spatial position effects on selective forms of object location memory

Prior research has demonstrated robust sex and sexual orientation-related differences in object location memory in humans. Here we show that this sexual variation may depend on the spatial position of target objects and the task-specific nature of the spatial array. We tested the recovery of object locations in three object arrays (object exchanges, object shifts, and novel objects) relative to veridical center (left compared to right side of the arrays) in a sample of 35 heterosexual men, 35 heterosexual women, and 35 homosexual men. Relative to heterosexual men, heterosexual women showed better location recovery in the right side of the array during object exchanges and homosexual men performed better in the right side during novel objects. However, the difference between heterosexual and homosexual men disappeared after controlling for IQ. Heterosexual women and homosexual men did not differ significantly from each other in location change detection with respect to task or side of array. These data suggest that visual space biases in processing categorical spatial positions may enhance aspects of object location memory in heterosexual women.

Sexual orientation perception involves gendered facial cues

Perceivers can accurately judge a face's sexual orientation, but the perceptual mechanisms mediating this remain obscure. The authors hypothesized that stereotypes casting gays and lesbians as gender "inverts," in cultural circulation for a century and a half, lead perceivers to use gendered facial cues to infer sexual orientation. Using computer-generated faces, Study 1 showed that as two facial dimensions (shape and texture) became more gender inverted, targets were more likely to be judged as gay or lesbian. Study 2 showed that real faces appearing more gender inverted were more likely to be judged as gay or lesbian. Furthermore, the stereotypic use of gendered cues influenced the accurate judgment of sexual orientation. Although using gendered cues increased the accuracy of sexual orientation judgments overall, Study 3 showed that judgments were reliably mistaken for targets that countered stereotypes. Together, the findings demonstrate that perceivers utilize gendered facial cues to glean another's sexual orientation, and this influences the accuracy or error of judgments.

Paraphilias across cultures: contexts and controversies

Cultures define and describe what is normal and what is deviant. These definitions of normality vary across cultures and are influenced by a number of factors, such as religion. Cultures have been described in various ways, including sex-positive where the sexual act itself is seen as important for pleasure, or sex-negative where the sexual act is seen only as for procreative purposes. The role and development of paraphilias across cultures is also variable, with cultures defining what is legal or illegal. Such differences make collection of epidemiological data and comparison across paraphilias problematic. This discussion suggests that characteristics of cultures may influence the rate of reporting paraphilias, as well as the rate of paraphilias themselves. Furthermore, with increased industrialization and urbanization, families will become more nuclear, with attitudes toward sex and paraphilias changing as well. This review also explores whether paraphilias can be seen as culture-bound syndromes, and recommends consideration of a number of conceptual issues regarding the diagnosis and prevalence of paraphilias as future cross-cultural studies on this topic are developed.

Genetic and environmental effects on same-sex sexual behavior: a population study of twins in Sweden

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.