Genetic and environmental influences on risky sexual behaviour and its relationship with personality

Exploring Relationships Between Internalizing Problems and Risky Sexual Behavior: A Twin Study

Previous research links risky sexual behavior (RSB) to externalizing problems and to substance use, but little research has been conducted on relationships between internalizing problems (INT) and RSB. The current study addresses that literature gap, using both a twin sample from Colorado (N = 2567) and a second twin sample from Minnesota (N = 1131) in attempt to replicate initial results. We explored the hypothesis that the latent variable INT would be more strongly associated with the latent variable RSB for females than for males, examining relationships between INT and RSB via phenotypic confirmatory factor analysis and multivariate twin analyses. We found a small but significant phenotypic association between the latent variables. However, despite using two large twin samples, limited power restricted our ability to identify the genetic and environmental mechanisms underlying this association. Our sex differences hypothesis was not fully supported in either sample and requires further investigation. Our findings illustrate the complexity of the relationship between internalizing problems and risky sexual behavior.

Causal Influences of Same-Sex Attraction on Psychological Distress and Risky Sexual Behaviors: Evidence for Bidirectional Effects

Although health disparities among same-sex attracted compared to heterosexual individuals are typically explained by minority stress, there is limited evidence for a causal effect. This study investigated whether same-sex attraction was causally associated with psychological distress and risky sexual behavior using sociosexual behavior as a proxy. The sample comprised monozygotic and dizygotic twins and their non-twin siblings (n = 2036, 3780 and 2356, respectively) genotyped and assessed for same-sex attraction, psychological distress (anxiety and depressive symptoms), and risky sexual behavior. Causal influences were investigated with same-sex attraction as the predictor and psychological distress and risky sexual behavior as the outcomes in two separate Mendelian Randomization-Direction of Causation (MRDoC) models using OpenMx in R. The MRDoC model improves on the Mendelian Randomization and Direction of Causation twin models by allowing analyses of variables with similar genetic architectures, incorporating polygenic scores as instrumental variables and specifying pleiotropy and residual covariance. There were significant causal influences flowing from same-sex attraction to psychological distress and risky sexual behavior (standardized coefficients = 0.13 and 0.16; 95% CIs 0.03-0.23 and 0.08-0.25, respectively). Further analyses also demonstrated causal influences flowing from psychological distress and risky sexual behavior toward same-sex attraction. Causal influences from same-sex attraction to psychological distress and risky sexual behavior may reflect minority stress, which reinforces ongoing measures to minimize social disparities. Causal influences flowing in the opposite direction may reflect rejection sensitivity, stigma-inducing outcomes of risky sexual behavior, and recall bias; however, further research is required to specifically investigate these processes.

Time Goes Back-Time Perspective in Polish Men with Compulsive Sexual Behavior Disorder and Risky Sexual Behavior

Many relationships between time perspective and a propensity to engage in risky behaviors or developing addictions have been demonstrated. The aim of our study was to determine the differences in intensity of individual time perspectives in people with compulsive sexual behavior disorder (CSBD) and risky sexual behavior (RSB). The analysis includes 425 men: 98 CSBD (age M = 37.99 years), 63 RSB (age M = 35.70 years), 264 without CSBD and RSB features constituting the control group (age M = 35.08 years). We used the Zimbardo Time Perspective Inventory, the Sexual Addiction Screening Test-Revised, the Risky Sexual Behavior Scale and a self-constructed survey. The comparative analysis showed a higher intensity of past-negative (p = 0.040), a lower of past-positive (p < 0.001) and a present-fatalistic (p = 0.040) outlook in the CSBD group compared to the control group. Compared to the participants with RSB, the CSBD group was characterized by a higher intensity of past-negative (p = 0.010), a lower of past-positive (p = 0.004) and a present-hedonistic perspective (p = 0.014). The RSB group also achieved higher results from the present-hedonistic perspective (p = 0.046) compared to the control group. The CSBD patients indicate a stronger tendency to focus on negative past compared to non-CSBD men, both taking and not taking RSB. The time perspective profiles of RSB men are similar to those who do not engage in RSB. The distinguishing feature of men with RSB without CSBD is a greater ability to enjoy current experiences.

Factor Structure of the Sexual Risk Survey Among U.S. College Students with and without ADHD: Assessing Clinical Utility with a High-Risk Population

Young adults, particularly college students, report a higher prevalence of risky sexual behavior than the general population, increasing their likelihood for unplanned pregnancy, sexually transmitted infections (STIs), and negative psychological outcomes. Although sexual risk behavior and its consequences are a major public health concern, current prevention literature is insufficient and relies on sexual risk measures with limited psychometric support. The present study, therefore, examined the psychometric properties of a sexual risk survey (SRS; Turchik, Garske, in Arch Sex Behav 38:936-948, 2009), using data from the first year of a longitudinal study following the outcomes of college students with and without attention-deficit/hyperactivity disorder (ADHD; N = 410). Principal components analyses were conducted to assess the factorial structure of the SRS comparing results from a general college population and a college population considered to be high-risk (ADHD). Results revealed four components across both samples. Internal consistency estimates for component scores and total scores ranged from .627 to 918. Implications of the findings are discussed and suggestions for future studies are advanced.

Associations between the CADM2 gene, substance use, risky sexual behavior, and self-control: A phenome-wide association study

Risky behaviors, such as substance use and unprotected sex, are associated with various physical and mental health problems. Recent genome-wide association studies indicated that variation in the cell adhesion molecule 2 (CADM2) gene plays a role in risky behaviors and self-control. In this phenome-wide scan for risky behavior, it was tested if underlying common vulnerability could be (partly) explained by pleiotropic effects of this gene and how large the effects were. Single nucleotide polymorphism (SNP)-level and gene-level association tests within four samples (25 and Up, Spit for Science, Netherlands Twin Register, and UK Biobank and meta-analyses over all samples (combined sample of 362,018 participants) were conducted to test associations between CADM2, substance- and sex-related risk behaviors, and various measures related to self-control. We found significant associations between the CADM2 gene, various risky behaviors, and different measures of self-control. The largest effect sizes were found for cannabis use, sensation seeking, and disinhibition. Effect sizes ranged from 0.01% to 0.26% for single top SNPs and from 0.07% to 3.02% for independent top SNPs together, with sufficient power observed only in the larger samples and meta-analyses. In the largest cohort, we found indications that risk-taking proneness mediated the association between CADM2 and latent factors for lifetime smoking and regular alcohol use. This study extends earlier findings that CADM2 plays a role in risky behaviors and self-control. It also provides insight into gene-level effect sizes and demonstrates the feasibility of testing mediation. These findings present a good starting point for investigating biological etiological pathways underlying risky behaviors.

Dissecting polygenic signals from genome-wide association studies on human behaviour

Genome-wide association studies on human behavioural traits are producing large amounts of polygenic signals with significant predictive power and potentially useful biological clues. Behavioural traits are more distal and are less directly under biological control compared with physical characteristics, which makes the associated genetic effects harder to interpret. The results of genome-wide association studies for human behaviour are likely made up of a composite of signals from different sources. While sample sizes continue to increase, we outline additional steps that need to be taken to better delineate the origin of the increasingly stronger polygenic signals. In addition to genetic effects on the traits themselves, the major sources of polygenic signals are those that are associated with correlated traits, environmental effects and ascertainment bias. Advances in statistical approaches that disentangle polygenic effects from different traits as well as extending data collection to families and social circles with better geographical coverage will probably contribute to filling the gap of knowledge between genetic effects and behavioural outcomes.

Advancing the Psychometric Study of Human Life History Indicators : K Does Not Measure Life History Speed, but Theory and Evidence Suggest It Deserves Further Attention

In this article we attend to recent critiques of psychometric applications of life history (LH) theory to variance among humans and develop theory to advance the study of latent LH constructs. We then reanalyze data (n = 4,244) previously examined by Richardson et al. (Evolutionary Psychology, 15(1), 2017, https://doi.org/10.1177/1474704916666840 to determine whether (a) previously reported evidence of multidimensionality is robust to the modeling approach employed and (b) the structure of LH indicators is invariant by sex. Findings provide further evidence that a single LH dimension is implausible and that researchers should cease interpreting K-factor scores as empirical proxies for LH speed. In contrast to the original study, we detected a small inverse correlation between mating competition and Super-K that is consistent with a trade-off. Tests of measurement invariance across the sexes revealed evidence of metric invariance (i.e., equivalence of factor loadings), consistent with the theory that K is a proximate cause of its indicators; however, evidence of partial scalar invariance suggests use of scores likely introduces bias when the sexes are compared. We discuss limitations and identify approaches that researchers may use to further evaluate the validity of the K-factor and other applications of LH to human variation.

Effects of Fathers on Adolescent Daughters' Frequency of Substance Use and Risky Sexual Behavior

This research: (1) implements a genetically informed design to examine the effects of fathers' presence-absence and quality of behavior during childhood/adolescence on daughters' frequency of substance use during adolescence; and (2) tests substance use frequency as mediating the relation between paternal behavior and daughters' sexual risk taking. Participants were 223 sister dyads from divorced/separated biological families. Sisters' developmental exposure to socially deviant paternal behavior predicted their frequency of tobacco, alcohol, and cannabis (TAC) use. Older sisters who co-resided with fathers who were more (vs. less) socially deviant reported more frequent TAC use during adolescence. More frequent TAC use predicted more risky sexual behavior for these daughters. No effects were found for younger sisters, who spent less time living with their fathers.

Mental Health Disparities Mediating Increased Risky Sexual Behavior in Sexual Minorities: A Twin Approach

Increased risky sexual behavior in sexual minorities relative to heterosexual individuals may be partly explained by mental health disparities, and both factors may be further jointly influenced by common genetic and environmental factors. However, these relationships have not been previously investigated. The objectives of the present study were to investigate mental health disparities as a mediator of the relationship between sexual orientation and risky sexual behavior, controlling for genetic and environmental effects in this relationship and testing for sex differences. Participants included 5814 twins from a Finnish twin cohort. Specified latent factors included sexual orientation, mental health indicators, and risky sexual behavior. Twin models were fitted to the factor structure of the data whereby a Cholesky decomposition on the factors was compared to a mediation submodel using OpenMx. Sex differences were tested in the final model. Phenotypically, mental health disparities partially mediated the relationship between sexual orientation and increased risky sexual behavior, with comparable effects in males and females. However, while this indirect route from sexual orientation to risky sexual behavior mainly contained transmitted genetic effects in males, there was a significant proportion of transmitted shared environmental effects in females. This is the first study to demonstrate that the mediation relationships between sexual orientation, mental health disparities, and risky sexual behavior are not confounded by genetic and environmental factors. The significant sex differences need to be recognized in future research and intervention design to improve sexual health in sexual minorities.

Nick Martin's Contributions to Human Sexuality Research

Genetic research into human sexuality was scarce at the end of last century. In 1992 Nick developed a 12-page questionnaire to send to twins to investigate the underpinnings of sexuality. The questionnaire included items about sexual orientation, sociosexuality and sexual behavior, and was completed by almost 5000 twins. The resulting data, unique at the time, has been used to investigate many previously unexaminable research questions. Here we describe how Nick's questionnaire contributed to our understanding of human sexuality and how we got involved in this endeavor.

Sexual Development in Adolescence: An Examination of Genetic and Environmental Influences

Sexual development entails many experiences and is a major feature of adolescence. Most relevant behavioral genetic studies, however, focus primarily on sexual behaviors associated with health risks. We took a more normative, developmental perspective by examining genetic and environmental influences on five sexual behaviors ranging from dating to pregnancy in middle (M_age  = 14.90 years) and late adolescence (M_age  = 17.85 years) in a sample of twins (N = 3,762). Overall, behaviors that are more common and socially sanctioned (e.g., dating) were more heritable than behaviors that are less common and socially acceptable (e.g., sexual intercourse). That the etiology of different sexual behaviors is tied to their normativeness highlights the importance of considering the broader developmental context when studying sexual development.

A Life History Approach to the Female Sexual Orientation Spectrum: Evolution, Development, Causal Mechanisms, and Health

Women's capacity for sexual fluidity is at least as interesting a phenomenon from the point of view of evolutionary biology and behavioral endocrinology as exclusively homosexual orientation. Evolutionary hypotheses for female nonheterosexuality have failed to fully account for the existence of these different categories of nonheterosexual women, while also overlooking broader data on the causal mechanisms, physiology, ontogeny, and phylogeny of female nonheterosexuality. We review the evolutionary-developmental origins of various phenotypes in the female sexual orientation spectrum using the synergistic approach of Tinbergen's four questions. We also present femme-specific and butch-specific hypotheses at proximate and ultimate levels of analysis. This review article indicates that various nonheterosexual female phenotypes emerge from and contribute to hormonally mediated fast life history strategies. Life history theory provides a biobehavioral explanatory framework for nonheterosexual women's masculinized body morphology, psychological dispositions, and their elevated likelihood of experiencing violence, substance use, obesity, teenage pregnancy, and lower general health. This pattern of life outcomes can create a feedback loop of environmental unpredictability and harshness which destabilizes intrauterine hormonal conditions in mothers, leading to a greater likelihood of fast life history strategies, global health problems, and nonheterosexual preferences in female offspring. We further explore the potential of female nonheterosexuality to function as an alloparental buffer that enables masculinizing alleles to execute their characteristic fast life history strategies as they appear in the female and the male phenotype. Synthesizing life history theory with the female sexual orientation spectrum enriches existing scientific knowledge on the evolutionary-developmental mechanisms of human sex differences.

Are you fluent in sexual emoji?😉: Exploring the use of emoji in romantic and sexual contexts

This research presents an exploratory study of how individuals use emoji, specifically in sexually suggestive contexts. Emoji are small images that depict emotions, concepts, or items that are used in computer-mediated communication in order to add context, emotion, and personality to messages. The dataset consists of 693 participants recruited via online social networks and forums. Results indicate that the use of emoji play a significant role in the sending and receiving of sexually suggestive messages; of individuals who have sent these messages, 51% report that the use of emoji led to the sexually suggestive behaviour and 54% report that emoji appear in their messages sometimes, often, or always. The three most common object emoji last sent and received in a sexually suggestive message are the tongue (👅), the eggplant (🍆), and the sweat droplets (💦), while the three most common face emoji last sent and received in this context are the smirking face (😏), the winking face (😉), and the blowing a kiss face (😘). Additionally, this study demonstrates that extraversion and number of casual sexual partners is significantly related to the use of sexually suggestive emoji, as both extraversion and numbers of casual sexual partners account for 5.9% of the shared variance in the use of sexual emoji. This research provides empirical information that may be used to guide future research into the use of emoji in computer-mediated communication.

The genetics of human personality

Personality traits are the relatively enduring patterns of thoughts, feelings and behaviors that reflect the tendency to respond in certain ways under certain circumstances. Twin and family studies have showed that personality traits are moderately heritable, and can predict various lifetime outcomes, including psychopathology. The Research Domain Criteria characterizes psychiatric diseases as extremes of normal tendencies, including specific personality traits. This implies that heritable variation in personality traits, such as neuroticism, would share a common genetic basis with psychiatric diseases, such as major depressive disorder. Despite considerable efforts over the past several decades, the genetic variants that influence personality are only beginning to be identified. We review these recent and increasingly rapid developments, which focus on the assessment of personality via several commonly used personality questionnaires in healthy human subjects. Study designs covered include twin, linkage, candidate gene association studies, genome-wide association studies and polygenic analyses. Findings from genetic studies of personality have furthered our understanding about the genetic etiology of personality, which, like neuropsychiatric diseases themselves, is highly polygenic. Polygenic analyses have showed genetic correlations between personality and psychopathology, confirming that genetic studies of personality can help to elucidate the etiology of several neuropsychiatric diseases.

Sexuality in Older Couples: Individual and Dyadic Characteristics

Sexuality is a key component of health and functioning that changes with age. Although most sexual activity takes place with a partner, the majority of research on sexuality has focused on individuals. In this paper, we focused on the sexual dyad. We proposed and tested a conceptual model of the predictors of partnered sexual activity in older adulthood. This model began with the personality of each of the partners, which affects individuals' views of sex and characteristics of the partnership, which in turn affected sexual expression in the couple. We measured a key feature of personality, Positivity, which reflected the individual's tendency to present his or herself positively in social situations. This trait, we posited, increased frequency of sex through increased desire for sex, and the subjective importance of sex to each member of the couple. In this model, Positivity also impacted characteristics of the relationship that promoted dyadic sexual behavior. These processes differed for men and women in the model. We tested this model with data from the National Social Life, Health and Aging Project, which conducted personal interviews with both partners in 940 American dyads (average male age 72; average female age 69). We found that couples in which the husbands' (but not wives') were high in Positivity show higher levels of sexual activity, and that this association was partially mediated by dimensions of relationship quality, but more so by individual factors such as thinking about sex and believing sex is important.

Alcohol-related genes show an enrichment of associations with a persistent externalizing factor

Research using twins has found that much of the variability in externalizing phenotypes-including alcohol and drug use, impulsive personality traits, risky sex, and property crime-is explained by genetic factors. Nevertheless, identification of specific genes and variants associated with these traits has proven to be difficult, likely because individual differences in externalizing are explained by many genes of small individual effect. Moreover, twin research indicates that heritable variance in externalizing behaviors is mostly shared across the externalizing spectrum rather than specific to any behavior. We use a longitudinal, "deep phenotyping" approach to model a general externalizing factor reflecting persistent engagement in a variety of socially problematic behaviors measured at 11 assessment occasions spanning early adulthood (ages 18 to 28). In an ancestrally homogenous sample of non-Hispanic Whites (N = 337), we then tested for enrichment of associations between the persistent externalizing factor and a set of 3,281 polymorphisms within 104 genes that were previously identified as associated with alcohol-use behaviors. Next, we tested for enrichment among domain-specific factors (e.g., property crime) composed of residual variance not accounted for by the common factor. Significance was determined relative to bootstrapped empirical thresholds derived from permutations of phenotypic data. Results indicated significant enrichment of genetic associations for persistent externalizing, but not for domain-specific factors. Consistent with twin research findings, these results suggest that genetic variants are broadly associated with externalizing behaviors rather than unique to specific behaviors. (PsycINFO Database Record

Potentially traumatic events, personality, and risky sexual behavior in undergraduate college students

OBJECTIVE

Impulsivity and extraversion have demonstrated associations with risky sexual behavior (RSB) and potentially traumatic events (PTEs). In addition, interpersonal trauma appears to be associated with RSB, but research on the relationship between RSB and noninterpersonal PTEs (e.g., accidental) is lacking. The current study aims to investigate the relationships between personality (i.e., impulsivity, extraversion), RSB and multiple types of PTEs (i.e., accidental, physical, or sexual).

METHOD

Personality and demographic characteristics were assessed during participants' (N = 970) first semester of college, past-12 month PTEs and RSB were assessed during the second semester of participants' junior year. Multiple linear regression was used to examine the relationship between PTEs, personality factors, and RSB. Analyses were also conducted to examine the potential mediating effect of interpersonal PTEs on the relationship between personality and RSB.

RESULTS

Impulsivity and extraversion were significantly positively associated with RSB. Both physical and sexual PTEs, but not accidental PTEs, were also significantly positively associated with RSB. Sexual PTEs significantly mediated the relationship between impulsivity and RSB.

CONCLUSIONS

This is the first study to date to simultaneously examine the relationship between personality, RSB, and types of PTEs in a large sample of young adults. Exposure to interpersonal trauma appears to be a salient factor in the relationship between personality, specifically impulsivity, and RSB. These results indicate that college students may benefit from education regarding the potential negative outcomes of RSB, and that individuals with a history of interpersonal PTEs may be at increased risk for sexual risk taking. (PsycINFO Database Record

A Sex-Positive Framework for Research on Adolescent Sexuality

In this article, I propose a sex-positive framework for research on adolescent sexuality in which I consider consensual sexual activities in adolescence as developmentally normative and potentially healthy. The sex-positive framework is contrasted with the predominant "risk" perspective that presumes that abstinence from sexual activity is the ideal behavioral outcome for teenagers. Evidence from longitudinal and behavioral genetic studies indicates that engaging in sexual intercourse in adolescence does not typically cause worse psychological functioning. The relationship context of sexual experience may be a critical moderator of its psychological impact. Moreover, cross-cultural data on adolescents' contraception usage, unintended pregnancy, and sexually transmitted infections suggest that, despite the unacceptably high rate of negative health consequences among U.S. teenagers, adolescents can have the developmental capacity to regulate the health risks inherent in sexual activity. Understanding adolescent sexuality can be fostered by considering sexual well-being, a multidimensional construct that incorporates an adolescent's sexual self-efficacy, sexual self-esteem, feelings of sexual pleasure and satisfaction, and freedom from pain and negative affect regarding sexuality. New research is necessary to understand the development of adolescent sexual well-being, including its normative age trends, its reciprocal links with sexual behavior, and its impact on psychological and physical health.

The relationship between future time perspective, self-efficacy and risky sexual behaviour in the Black youth of central South Africa

BACKGROUND

An interest exists in understanding why adolescents partake in risky sexual behaviours, as well as the risk and protective practices associated with risky sexual behaviour.

AIM

The aim of this study was to investigate the moderator effect of future time perspective in the relationship between self-efficacy and risky sexual behaviour.

METHODS

A random cluster consisting of 467 learners from English medium high schools of central South Africa participated in this study. The participants' risky sexual behaviour, self-efficacy and future time perspective were measured with the Perceptions of HIV/AIDS Risk Survey, Generalised Perceived Self-efficacy Scale and the Zimbardo Time Perspective Inventory, respectively. Product term regression analysis was performed.

RESULTS

It was found that both self-efficacy and future time perspective were negatively related to risky sexual behaviour. No moderating effect was found for future time perspective in the relationship between self-efficacy and risky sexual behaviour.

CONCLUSIONS

Self-efficacy and future time perspective were identified as qualities that protect adolescents from engaging in risky sexual behaviours. This finding can be useful in developing prevention programmes. Intervention programmes aimed at the youth should foster a sense of hope and possibility about the future and the development of goals and aspirations to prevent risky behaviour.

Gender-related differences in the associations between sexual impulsivity and psychiatric disorders

OBJECTIVE

Sexual impulsivity (SI) has been associated with conditions that have substantial public health costs, such as sexually transmitted infections and unintended pregnancies. However, SI has not been examined systematically with respect to its relationships to psychopathology. We aimed to investigate associations between SI and psychopathology, including gender-related differences.

METHOD

We performed a secondary data analysis of Wave-2 of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), a national sample of 34,653 adults in the United States. DSM-IV-based diagnoses of mood, anxiety, drug and personality disorders were assessed using the Alcohol Use Disorder and Associated Disabilities Interview Scheduled DSM-IV Version.

RESULTS

The prevalence of SI was considerable (14.7%), with greater acknowledgment by men than women (18.9% versus 10.9%; p < 0.0001). For both women and men, SI was positively associated with most Axis-I and Axis-II psychiatric disorders (OR range: Women, Axis-I:1.89-6.14, Axis-II:2.10-10.02; Men, Axis-I:1.92-6.21, Axis-II:1.63-6.05). Significant gender-related differences were observed. Among women as compared to men, SI was more strongly associated with social phobia, alcohol abuse/dependence, and paranoid, schizotypal, antisocial, borderline, narcissistic, avoidant and obsessive-compulsive personality disorders.

CONCLUSION

The robust associations between SI and psychopathology across genders suggest the need for screening and interventions related to SI for individuals with psychiatric concerns. The stronger associations between SI and psychopathology among women as compared to men emphasize the importance of a gender-oriented perspective in targeting SI. Longitudinal studies are needed to determine the extent to SI predates, postdates or co-occurs with specific psychiatric conditions.

Substance use and sexual intercourse onsets in adolescence: a genetically informative discordant twin design

PURPOSE

Using a genetically informed, discordant twin analysis, the objective of this study was to examine whether earlier onset of drinking and smoking behaviors predicted early sexual intercourse onset.

METHODS

Over 3,400 adult same-sex twins from the Australian Twin Registry completed a structured interview that included retrospective reports on onsets of smoking, drinking, intoxication, and sexual intercourse and conduct disorder symptoms. A two-level frailty model estimated within-twin-pair and between-twin-pair comparisons. Onsets of smoking, drinking, drunkenness, and conduct disorder symptoms were estimated as sexual intercourse onset predictors.

RESULTS

After controlling for conduct disorder, smoking and drinking onset did not predict sexual intercourse onset for either within-twin-pair or between-twin-pair comparisons. Drunkenness onset had a significant effect on sexual intercourse onset, such that twins who first experienced alcohol intoxication at a younger age than their co-twins were also more likely to have sex earlier than their co-twins.

CONCLUSIONS

Relationships between substance use and sexual intercourse onsets may be due mostly to shared underlying factors; there was only a small relation between intoxication onset and sexual intercourse onset, and no direct relation between smoking and drinking onset and sexual intercourse onset.

Genetic influences on adolescent sexual behavior: Why genes matter for environmentally oriented researchers

There are dramatic individual differences among adolescents in how and when they become sexually active adults, and early sexual activity is frequently cited as a cause of concern for scientists, policymakers, and the general public. Understanding the causes and developmental impact of adolescent sexual activity can be furthered by considering genes as a source of individual differences. Quantitative behavioral genetics (i.e., twin and family studies) and candidate gene association studies now provide clear evidence for the genetic underpinnings of individual differences in adolescent sexual behavior and related phenotypes. Genetic influences on sexual behavior may operate through a variety of direct and indirect mechanisms, including pubertal development, testosterone levels, and dopaminergic systems. Genetic differences may be systematically associated with exposure to environments that are commonly treated as causes of sexual behavior (gene-environment correlation). Possible gene-environment correlations pose a serious challenge for interpreting the results of much behavioral research. Multivariate, genetically informed research on adolescent sexual behavior compares twins and family members as a form of quasi experiment: How do twins who differ in their sexual experiences differ in their later development? The small but growing body of genetically informed research has already challenged dominant assumptions regarding the etiology and sequelae of adolescent sexual behavior, with some studies indicating possible positive effects of teenage sexuality. Studies of Gene × Environment interaction may further elucidate the mechanisms by which genes and environments combine to shape the development of sexual behavior and its psychosocial consequences. Overall, the existence of heritable variation in adolescent sexual behavior has profound implications for environmentally oriented theory and research.

Evaluation and treatment of sex addiction

There have been several diagnostic labels for persistent, excessive sexual behaviors, often referred in the popular media as sex addiction. Two related diagnoses, Internet addictive disorder and hypersexual disorder, were considered for, but not included in the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders. However, most clinicians, even those trained in sexual disorders or addiction medicine, have little to no training in treating sexual compulsivity and cybersex addiction. The authors present the historical context, proposed diagnostic criteria, evaluation protocols, comorbid disorders, speculations about the neuroscience, and treatment recommendations.

Genetics of impulsive behaviour

Impulsivity, defined as the tendency to act without foresight, comprises a multitude of constructs and is associated with a variety of psychiatric disorders. Dissecting different aspects of impulsive behaviour and relating these to specific neurobiological circuits would improve our understanding of the etiology of complex behaviours for which impulsivity is key, and advance genetic studies in this behavioural domain. In this review, we will discuss the heritability of some impulsivity constructs and their possible use as endophenotypes (heritable, disease-associated intermediate phenotypes). Several functional genetic variants associated with impulsive behaviour have been identified by the candidate gene approach and re-sequencing, and whole genome strategies can be implemented for discovery of novel rare and common alleles influencing impulsivity. Via deep sequencing an uncommon HTR2B stop codon, common in one population, was discovered, with implications for understanding impulsive behaviour in both humans and rodents and for future gene discovery.

Maintenance of genetic variation in human personality: testing evolutionary models by estimating heritability due to common causal variants and investigating the effect of distant inbreeding

Personality traits are basic dimensions of behavioral variation, and twin, family, and adoption studies show that around 30% of the between-individual variation is due to genetic variation. There is rapidly growing interest in understanding the evolutionary basis of this genetic variation. Several evolutionary mechanisms could explain how genetic variation is maintained in traits, and each of these makes predictions in terms of the relative contribution of rare and common genetic variants to personality variation, the magnitude of nonadditive genetic influences, and whether personality is affected by inbreeding. Using genome-wide single nucleotide polymorphism (SNP) data from > 8000 individuals, we estimated that little variation in the Cloninger personality dimensions (7.2% on average) is due to the combined effect of common, additive genetic variants across the genome, suggesting that most heritable variation in personality is due to rare variant effects and/or a combination of dominance and epistasis. Furthermore, higher levels of inbreeding were associated with less socially desirable personality trait levels in three of the four personality dimensions. These findings are consistent with genetic variation in personality traits having been maintained by mutation-selection balance.

Psychosexual Study of Communist Era Hungarian Twins

Our aim in this study is to describe the characteristics of sexual development in twins and estimate the role of heritability and environmental factors as causes of certain sexual disorders. Two hundred and ten adult same-sex twin pairs (92 monozygotic [MZ] female, 41 MZ male, 55 dizygotic [DZ] female and 22 DZ male pairs) were involved in the study. Data were collected in 1982 by self-administered questionnaires that included items on sexual maturation, sexual life, contraception, mutual sexual activity within twin pairs and alcohol use. The ratio of married to unmarried twins was nearly the same in MZs and DZs, with the exception that the divorce rate was higher in MZ female twins (14%), and DZ and male twins were slightly more likely to be single. Menarche was later in twins compared to non-twin Hungarian women. 57% of MZs experienced menarche within 3 months of each other, 77% within 6 months while it occurred for 30% and 43% respectively in DZs. The first seminal emission indicated some delay in male twins compared with the Hungarian general population sample. MZ first kisses occurred later than DZ's first kisses. The same was true for the first petting, masturbation and first sexual intercourse. Anorgasmy is 27% heritable but the estimate is not statistically significant. Concordance rate for premature ejaculation in MZs was greater than in DZs but the structural equation model showed significant misfit. Age at menarche appeared to be strongly heritable.

Meta-analysis of genome-wide association studies identifies common variants in CTNNA2 associated with excitement-seeking

The tendency to seek stimulating activities and intense sensations define excitement-seeking, a personality trait akin to some aspects of sensation-seeking. This trait is a central feature of extraversion and is a component of the multifaceted impulsivity construct. Those who score high on measures of excitement-seeking are more likely to smoke, use other drugs, gamble, drive recklessly, have unsafe/unprotected sex and engage in other risky behaviors of clinical and social relevance. To identify common genetic variants associated with the Excitement-Seeking scale of the Revised NEO Personality Inventory, we performed genome-wide association studies in six samples of European ancestry (N=7860), and combined the results in a meta-analysis. We identified a genome-wide significant association between the Excitement-Seeking scale and rs7600563 (P=2 × 10(-8)). This single-nucleotide polymorphism maps within the catenin cadherin-associated protein, alpha 2 (CTNNA2) gene, which encodes for a brain-expressed α-catenin critical for synaptic contact. The effect of rs7600563 was in the same direction in all six samples, but did not replicate in additional samples (N=5105). The results provide insight into the genetics of excitement-seeking and risk-taking, and are relevant to hyperactivity, substance use, antisocial and bipolar disorders.

Early exposure to parents' relationship instability: implications for sexual behavior and depression in adolescence

PURPOSE

Examine the effects of the timing of parents' relationship instability on adolescent sexual and mental health.

METHODS

We assessed whether the timing of parents' relationship instability predicted adolescents' history of sexual partnerships (SP) and major depressive episodes. Multivariate logistic regression analyses controlled for potential mediators related to parenting and the family, including parent knowledge of activities, parent-child relationship quality, number of parents' post-separation relationship transitions, and number of available caregivers. Participants were assessed annually from age 5 through young adulthood as part of a multisite community sample (N = 585).

RESULTS

Participants who experienced parents' relationship instability before age 5 were more likely to report SP at age 16 (odds ratio [OR](adj) = 1.58) or an episode of major depression during adolescence (OR(adj) = 2.61). Greater parent knowledge at age 12 decreased the odds of SP at age 16, but none of the hypothesized parenting and family variables statistically mediated the association between early instability and SP or major depressive episode.

CONCLUSIONS

These results suggest that experiencing parents' relationship instability in early childhood is associated with sexual behavior and major depression in adolescence, but these associations are not explained by the parenting and family variables included in our analyses. Limitations of the current study and implications for future research are discussed.

Associations between dopamine D4 receptor gene variation with both infidelity and sexual promiscuity

BACKGROUND

Human sexual behavior is highly variable both within and between populations. While sex-related characteristics and sexual behavior are central to evolutionary theory (sexual selection), little is known about the genetic bases of individual variation in sexual behavior. The variable number tandem repeats (VNTR) polymorphism in exon III of the human dopamine D4 receptor gene (DRD4) has been correlated with an array of behavioral phenotypes and may be predicatively responsible for variation in motivating some sexual behaviors, particularly promiscuity and infidelity.

METHODOLOGY/PRINCIPAL FINDINGS

We administered an anonymous survey on personal history of sexual behavior and intimate relationships to 181 young adults. We also collected buccal wash samples and genotyped the DRD4 VNTR. Here we show that individuals with at least one 7-repeat allele (7R+) report a greater categorical rate of promiscuous sexual behavior (i.e., having ever had a "one-night stand") and report a more than 50% increase in instances of sexual infidelity.

CONCLUSIONS/SIGNIFICANCE

DRD4 VNTR genotype varies considerably within and among populations and has been subject to relatively recent, local selective pressures. Individual differences in sexual behavior are likely partially mediated by individual genetic variation in genes coding for motivation and reward in the brain. Conceptualizing these findings in terms of r/K selection theory suggests a mechanism for selective pressure for and against the 7R+ genotype that may explain the considerable global allelic variation for this polymorphism.

Cervix smear abnormalities: linking pathology data in female twins, their mothers and sisters

Mass screening for cervical cancer precursors has decreased the incidence of cervical cancer in several countries, including the Netherlands. Persistent infections of certain types of human papillomavirus are strongly associated with the development of cervical cancer. A number of factors may affect the liability to infection and subsequent progression to cervical intraepithelial neoplasia and cancer. This paper examines whether genetic factors are involved in explaining individual differences in liability. Data of 3178 women registered with the Netherlands Twin Register were successfully linked to the nationwide Dutch Pathology database that contains all results of mass screening for cervical cancer. The data from mono- and dizygotic twins and their female relatives were used to disentangle the influence of heritable and environmental factors on cervix smear abnormalities. Results showed that differences in cervix smear results clustered within families and resemblance was stronger in monozygotic twins (correlation 0.37, 95% confidence interval: 0.12-0.58) compared with other first-degree relatives (correlation 0.14, 95% confidence interval: -0.01-0.29). The familial clustering for an abnormal cervix smear is due to shared genetic factors that explain 37% of the variance in liability. The largest proportion of the variation in cervical smear abnormalities is due to unique environmental factors.

A genome-wide association study of Cloninger's temperament scales: implications for the evolutionary genetics of personality

Variation in personality traits is 30-60% attributed to genetic influences. Attempts to unravel these genetic influences at the molecular level have, so far, been inconclusive. We performed the first genome-wide association study of Cloninger's temperament scales in a sample of 5117 individuals, in order to identify common genetic variants underlying variation in personality. Participants' scores on Harm Avoidance, Novelty Seeking, Reward Dependence, and Persistence were tested for association with 1,252,387 genetic markers. We also performed gene-based association tests and biological pathway analyses. No genetic variants that significantly contribute to personality variation were identified, while our sample provides over 90% power to detect variants that explain only 1% of the trait variance. This indicates that individual common genetic variants of this size or greater do not contribute to personality trait variation, which has important implications regarding the genetic architecture of personality and the evolutionary mechanisms by which heritable variation is maintained.