Genetics of Human Sexual Behavior: Where We Are, Where We Are Going

The methodological and ethical concerns of genetic studies of same-sex sexual behavior

Same-sex sexual behavior has long interested genetics researchers in part because, while there is evidence of heritability, the trait as typically defined is associated with fewer offspring. Investigations of this phenomenon began in the 1990s with linkage studies and continue today with the advent of genome-wide association studies. As this body of research grows, so does critical scientific and ethical review of it. Here, we provide a targeted overview of existing genetics studies on same-sex sexual behavior, highlight the ethical and scientific considerations of this nascent field, and provide recommendations developed by the authors to enhance social and ethical responsibility.

From Waterloo to the Great Wall: A retrospective, multicenter study on the clinical practice and cultural attitudes in the management of premature ejaculation, in China

Premature ejaculation (PE), despite its wide prevalence, is largely underdiagnosed and undertreated. Being a multifactorial dysfunction with strong cultural characteristics, PE requires skillful attitudes in the psychosexological support, necessary to manage the patient's and the couple's expectations, as well as in the medical treatment. Dapoxetine is a short-acting selective serotonin reuptake inhibitor approved for use in lifelong and acquired PE in a number of countries. Opinions, not always generated by the evidence-based medicine, impacted the attitudes of Western andrologists, as a nocebo effect which produced a drug's Waterloo, characterized by low prescription rates much more built on the patients' and doctors' expectations than on costs, side effects, and efficacy. In the present study, we retrospectively reviewed real-life data from eight Andrology and Sexual Medicine Public Centers in China to assess the prevalence of PE among attending patients, its association with erectile dysfunction, its subtype, and the proposed treatments. In 2019, among 156,486 patients coming to the centers, 32,667 visits having PE as the chief complaint were performed (20.9%). Almost all patients received treatment prescriptions (32,641 patients, 99.92%); 23,273 patients came back for a follow-up visit in the subsequent 12 months (71.2% of those who initially received treatment). Dapoxetine, either alone or in combination with another therapy, was the most prevalent treatment, prescribed to 22,767 patients (69.7% of treated patients), followed by traditional Chinese medicine (TCM) (39.4%). At follow-up, 8174 patients were unsatisfied with treatment, and a new treatment was proposed (35.12%). Dapoxetine was the best treatment, with an overall 27.1% switching rate when used either alone or in combination: Although the switching rate for Dapoxetine alone was 44.2%, the association of the same drug with psychotherapy resulted in much lower rates (19.5%) and reached a minimum of 12% when also combined with TCM demonstrating how cultural aspects and medical attitudes may dramatically impact on the therapy of a multifaceted, complex, and culture-grounded sexual symptom such as PE. In conclusion, taking switching rates as surrogate markers of treatment failure, this real-life study-the largest in the field-shows that in a more patient-oriented (as in Chinese medical culture), and less symptom-oriented (as in Western medical attitudes), Dapoxetine is a successful treatment for PE patients, with higher reliability when used alone or as part of combined and integrated therapies.

Probing the genomic landscape of human sexuality: a critical systematic review of the literature

Whether human sexuality is the result of nature or nurture (or their complex interplay) represents a hot, often ideologically driven, and highly polarized debate with political and social ramifications, and with varying, conflicting findings reported in the literature. A number of heritability and behavioral genetics studies, including pedigree-based investigations, have hypothesized inheritance patterns of human sexual behaviors. On the other hand, in most twin, adoption, and nuclear family studies, it was not possible to disentangle between underlying genetic and shared environmental sources. Furthermore, these studies were not able to estimate the precise extent of genetic loading and to shed light both on the number and nature of the putative inherited factors, which remained largely unknown. Molecular genetic studies offer an unprecedented opportunity to overcome these drawbacks, by dissecting the molecular basis of human sexuality and allowing a better understanding of its biological roots if any. However, there exists no systematic review of the molecular genetics of human sexuality. Therefore, we undertook this critical systematic review and appraisal of the literature, with the ambitious aims of filling in these gaps of knowledge, especially from the methodological standpoint, and providing guidance to future studies. Sixteen studies were finally retained and overviewed in the present systematic review study. Seven studies were linkage studies, four studies utilized the candidate gene approach, and five studies were GWAS investigations. Limitations of these studies and implications for further research are discussed.

BGIG10116_34868: A Newly Discovered Gene Regulating Ejaculation Function

Ejaculation is a complex biphasic process involving a series of neurophysiological activities, such as the contraction of a large number of muscle groups and the ejaculation of semen from the urethra anterior. Due to the complexity of the process, many related factors have not been fully clarified, resulting in ejaculation dysfunction. As a common ejaculation dysfunction, lifelong premature ejaculation (LPE) is a problem for many people. Notably, gene polymorphism might play an important role in the etiology of LPE. However, the quest for identifying the actual genetic loci that contribute to LPE etiology has not been successful. Due to discrepancies in the design and methods of research, the correlation of most reports was not obtained in subjective replication experiments, and the conclusions may be inconsistent. In our study, three groups of ejaculation rats, namely, “rapid, normal, and delayed,” were selected based on the animal model of premature ejaculation (PE) in rats and the theory of ejaculation. Among them, the rats in the “rapid” ejaculation group can be used to stimulate humans with PE. Subsequently, we used the rat brain tissue for whole-transcriptome sequencing to screen the differential genes among the three groups. We tried to identify the actual genetic loci that contribute to PE etiology and provide a theoretical basis for the targeted therapy of PE.

Management of premature ejaculation: a clinical guideline from the Italian Society of Andrology and Sexual Medicine (SIAMS)

Premature ejaculation (PE) is the most prevalent male sexual dysfunction, and the most recently defined. PE is often mistakenly considered a purely psychosexological symptom by patients: the lacking awareness in regards to the pathophysiology and treatments often lead to resignation from the patients' side, making PE the most underdiagnosed sexual complaint. However, an ever-growing body of evidence supporting several organic factors has been developed in the last decades and several definitions have been suggested to encompass all defining features of PE. In the present document by the Italian Society of Andrology and Sexual Medicine (SIAMS), we propose 33 recommendations concerning the definition, pathophysiology, treatment and management of PE aimed to improve patient care. These evidence-based clinical guidelines provide the necessary up-to-date guidance in the context of PE secondary to organic and psychosexological conditions, such as prostate inflammation, endocrine disorders, and other sexual dysfunctions, and suggest how to associate pharmacotherapies and cognitive-behavioral therapy in a couple-centered approach. New therapeutic options, as well as combination and off-label treatments, are also described.

The serotonin transporter gene and female personality variation in a free-living passerine

Quantifying variation in behaviour-related genes provides insight into the evolutionary potential of repeatable among-individual variation in behaviour (i.e. personality). Yet, individuals typically also plastically adjust their behaviour in response to environmental conditions and/or age, thereby complicating the detection of genotype-phenotype associations. Here, using a population of free-living great tits (Parus major), we assessed the association between single nucleotide polymorphisms (SNPs) in the serotonin transporter gene (SERT) and two repeatable behavioural traits, i.e. female-female aggression and female hissing behaviour. For female-female aggression, a trait showing age-related plasticity, we found no evidence for associations with SERT SNPs, even when assessing potential age-dependent effects of SERT genotype on aggression. We also found no strong support for associations between SERT SNPs and hissing behaviour, yet we identified two synonymous polymorphisms (exon 13 SNP66 and exon 12 SNP144) of particular interest, each explaining about 1.3% of the total variation in hissing behaviour. Overall, our results contribute to the general understanding of the biological underpinning of complex behavioural traits and will facilitate further (meta-analytic) research on behaviour-related genes. Moreover, we emphasize that future molecular genetic studies should consider age-dependent genotype-phenotype associations for behavioural trait (co)variation, as this will vastly improve our understanding of the proximate causes and ultimate consequences of personality variation in natural populations.

Gene Variants in Premature Ejaculation: Systematic Review and Future Directions

INTRODUCTION

A growing number of genetic association studies have been performed to investigate the association between the genetic susceptibility alleles and the risk of premature ejaculation (PE); however, the results remain inconclusive.

OBJECTIVES

This systematic review aimed: (i) to determine whether an association exists between gene(s) or allelic variant(s) and PE; (ii) to assess whether the associations are consistent across studies in magnitude and direction, and (iii) to identify any limitation, gap, or shortcoming in the included studies.

METHODS

The literature search was conducted in PubMed, MEDLINE, Scopus, Cochrane Library, EMBASE, Academic Search Complete, Google Scholar, and CINAHL databases.

RESULTS

Different gene variants associated with PE were assessed. 25 genetic association studies met the inclusion criteria that investigated 11 genes, 2,624 men with PE compared with 9,346 men as controls, twins, and siblings. 19 studies demonstrated a significant association with PE, whereas 4 studies denied such a relationship. SLC6A4 gene polymorphism was investigated in 11 studies (7 studies demonstrated a significant relationship with PE, and 4 studies denied such a relationship). Dopamine transporter gene (DAT1) polymorphism was investigated in 4 studies exhibiting a significant relationship. Androgen receptor gene polymorphisms were investigated in 2 studies, 1 with a significant relationship and the other with a non-significant relationship. Oxytocin gene polymorphisms and tryptophan hydroxylase 2 gene polymorphisms were investigated in 2 studies with a significant relationship.

CONCLUSION

While this review has highlighted several genes that may be potentially associated with PE such as SLC6A4, limitations such as variance in study methods, lack of robust findings, small sample sizes, lack of reproducibility, quality of reporting, and quality of assessment remain a major concern. Further efforts such as standardizing reporting, exploring complementary designs, and the use of genome-wide association studies technology are warranted to test the reproducibility of these early findings. Mostafa T, Abdel-Hamid IA, Taymour M, et al. Gene Variants in Premature Ejaculation: Systematic Review and Future Directions. Sex Med Rev 2020;8:586-602.

Serotonergic polymorphisms in the control of ejaculation

Serotonin has long been implicated in the regulation of the processes that trigger the ejaculatory reflex. Most evidence of serotonergic involvement is, however, indirect, stemming either from studies on rodents or clinical trials investigating effects of serotonergic drugs. In the past decade, emerging evidence for heritability (i.e., genetic effects) of premature ejaculation (PE) symptoms has spawned a number of scholarly attempts to identify genes that regulate ejaculation, most of which have focused on candidate genes related to the serotonergic system. The aim of the present review article was to summarize the literature concerning genetic association studies of PE, with focus on serotonergic genes. However, methodological obstacles relating to the candidate gene approach predict that a priori hypotheses regarding candidate genes are likely to generate ambiguous and spurious results if samples (e.g., if samples are underpowered and/or stratified). Attempts to replicate reported novel associations between PE symptoms and serotonergic candidate genes have largely failed (thereby adding to the growing body of evidence casting doubt on the reliability of the candidate gene approach), and at present, it is not possible to determine with acceptable certainty which serotonergic genes, if any, are involved in ejaculatory function.

Innovations, Reviews and Proposals on the DSM-5: the Case of Sexual Dysfunctions, Gender Dysphoria and Paraphilic Disorders

Human behaviours have different meanings according to the historical moment and context. In this article sexual behaviours are taken as a category in order to analyse how psychiatric nosology is structured, as manifested in texts such as the DSM-5. The development of these diagnostic manuals are tools that are far from being free of subjectivities and interference of elements of power, expressed in the way health, illness, mental health, and mental disorders, are assumed; in short, the normal and pathological. Each new diagnosis, or even its elimination, and the recomposing of the different diagnostic criteria, especially in the field of sexual behaviour, present visions of how individual and collective human life is conceived, as well as an expression of accurate attempts to control human sexualities through the medicalisation of behaviour, coupled with moral, religious, and even legal considerations. Categories such as gender dysphoria, paraphilia or paraphilic disorders are examples of how the limits intended to establish a biomedical perspective are also incomplete and imprecise. These violate individual and social construction of sexualities and the conception of mental health, showing persistent difficulties and controversies that are evident in the way psychiatric classifications are made.

Mating Strategies and Sexual Functioning in Personality Disorders: A Comprehensive Review of Literature

INTRODUCTION

Personality disorders impair several aspects of intrapsychic and interpersonal life. In particular, mating strategies and sexual functioning could manifest in different and/or dysfunctional ways in people with personality disorders.

AIM

To describe, through a comprehensive review of the literature, the mating strategies and sexual functioning in patients with personality disorders.

METHODS

We listed and discussed the principal studies on the relation between mating strategies and sexual functioning in personality disorders. The search strategy used search terms in PubMed for the main studies published from January 2000 to December 2016.

MAIN OUTCOME MEASURES

We considered two main sections for our selection according to the aim of the present review: mating and sexuality.

RESULTS

Interesting evidence on mating strategies in personality disorders was found. In particular, the major items were found in the dramatic-unpredictable cluster, with borderline personality disorder being the most studied. In contrast, the bizarre-eccentric cluster had fewer items, with the schizoid personality disorder being the least studied. For sexual behavior, borderline personality seems to be the unique disorder sufficiently studied, with evidence of major histories of child sexual abuse, the presence of sexual dysfunctions, and paraphilic interests.

CONCLUSION

A large spectrum of mating strategies characterizes different personality disorders, although an inconsistent knowledge about the relation between sexual function and personality disorders emerged from our analysis of the literature. Hence, we invite clinicians and researchers to integrate psychodiagnostic and sexual assessments in psychiatric disciplines for people with personality disorders. Collazzoni A, Ciocca G, Limoncin E, et al. Mating Strategies and Sexual Functioning in Personality Disorders: A Comprehensive Review of Literature. Sex Med Rev 2017;5:414-428.

No Evidence for Long-Term Causal Associations Between Symptoms of Premature Ejaculation and Symptoms of Anxiety, Depression, and Sexual Distress in a Large, Population-Based Longitudinal Sample

Premature ejaculation (PE) is one of the most common male sexual complaints, but its etiology is unclear. Psychological problems, such as symptoms of anxiety and depression, have traditionally been seen as causal or maintaining etiological components of PE, and previous cross-sectional studies have found weak positive associations between them. The aim of the present study was to test possible causal pathways over time between PE and symptoms of the psychological problems anxiety, depression, and sexual distress. A sample of 985 male Finnish twins and brothers of twins completed a questionnaire in 2006 and 2012. Significant bivariate correlations were found both within and across time between PE and the psychological problems. When fitting structural equation models to test hypothesized causal pathways, symptoms of anxiety and sexual distress at the first measurement time point did not predict future PE. Likewise, PE symptoms at the first measurement did not predict increments or decrements in anxiety, sexual distress, or depression later on. These null findings regarding hypothesized associations may partly be explained by the relatively long time between measurements, or that the measures possibly did not capture the aspects of anxiety that are related to PE.

Lifestyle Factors and Premature Ejaculation: Are Physical Exercise, Alcohol Consumption, and Body Mass Index Associated With Premature Ejaculation and Comorbid Erectile Problems?

INTRODUCTION

Premature ejaculation (PE) is a common sexual problem in men, but its etiology remains uncertain. Lifestyle factors have long been hypothesized to be associated with sexual problems in general and have been proposed as risk factors for PE.

AIM

To explore associations among physical exercise, alcohol use, body mass index, PE, and erectile dysfunction.

METHODS

A population-based sample of Finnish men and a sample of Finnish men diagnosed with PE were surveyed for statistical comparisons. Participants using selective serotonin reuptake inhibitors or other medications known to affect symptoms of PE were excluded from analyses.

MAIN OUTCOME MEASURES

Self-report questionnaires: Multiple Indicators of Premature Ejaculation, International Index of Erectile Function-5, Alcohol Use Disorders Identification Test, and Godin Leisure-Time Exercise Questionnaire.

RESULTS

The clinical sample reported lower levels of physical exercise (mean = 27.53, SD = 21.01, n = 69) than the population-based sample (mean = 34.68, SD = 22.82, n = 863, t930 = 2.52, P = .012), and the effect size was large (d = 0.85). There was a small negative correlation between levels of physical exercise and symptoms of PE (r = -0.09, P < .01, n = 863) in the population-based sample. The association between physical exercise and PE remained significant after controlling for effects of age, erectile dysfunction, alcohol use, and body mass index.

CONCLUSION

If future studies show that the direction of causality of this association is such that physical activity alleviates PE symptoms, then including physical activity in PE treatment interventions could be a promising addition to treatment regimes.

Interplay Between Premature Ejaculation and Erectile Dysfunction: A Systematic Review and Meta-Analysis

INTRODUCTION

The specific determinants and underlying factors linking erectile dysfunction (ED) and premature ejaculation (PE) have yet to be clearly identified.

AIM

The aim of this study was to review and meta-analyze all available data regarding the link between ED and PE.

METHODS

An extensive Medline Embase and Cochrane search was performed including the following words: "premature ejaculation" and "erectile dysfunction".

MAIN OUTCOME MEASURES

All observational trials comparing the risk of ED in relation to PE were included. Data extraction was performed independently by two of the authors (G.R, G.C.), and conflicts resolved by the third investigator (M.M.).

RESULTS

Out of 474 retrieved articles, 18 were included in the study for a total of 57,229 patients, of which 12,144 (21.2%) had PE. The presence of PE, however defined, was associated with a significant increase in ED risk (odds ratio: 3.68[2.61;5.18]; P < 0.0001). Meta-regression analysis showed that the risk of ED in PE subjects was higher in older individuals as well as in those with a lower level of education and in those who reported a stable relationship less frequently. In addition, subjects with PE and ED more often reported anxiety and depressive symptoms and a lower prevalence of organic associated morbidities, including diabetes mellitus, hypertension and dyslipidemia. All the latter associations were confirmed even after adjustment for age. Finally the risk of PE-related ED increased with the increased proportion of acquired ejaculatory problems (adj r = 0.414; P < 0.0001 after the adjustment for age).

CONCLUSIONS

In conclusion, the present data showed that ED and PE are not distinctly separate entities, but should be considered from a dimensional point of view. Understanding this dimensional perspective might help sexual health care professionals in providing the most appropriate therapeutic approach to realistically increase patient related outcomes in sexual medicine.