Psychoticism as a dimension of personality: A multivariate genetic test of Eysenck and Eysenck's psychoticism construct

Validity, reliability and hierarchical structure of the PID-5 among Egyptian college students: Using exploratory structural equation modelling

BACKGROUND

The present study aimed to investigate the pathological personality traits of undergraduate students using the Personality Inventory for DSM-5 (PID-5) among Egyptian university-age participants.

METHOD

We replicated the five-factor model of the PID-5 using exploratory structural equation modelling analysis with target rotation towards the original study of the PID-5 construction. Next, we estimated the factor congruence to identify the similarity of the present five-factor solution with the available relevant studies. Moreover, we investigated the pattern of the Personality Pathology hierarchy for the PID-5. The sample comprised 845 undergraduate students whose ages ranged between 18 and 28 years (mean = 19.89 and standard deviation = 1.43).

RESULTS

The present study findings showed that the reliability of the PID-5 facets was acceptable. In addition, the factor congruence results showed that the replicated five factors had acceptable congruence coefficients with some relevant studies. Also, the results indicated that the hierarchy levels were found to be consistent with some relevant findings.

DISCUSSION

Generally, the PID-5 showed sufficient reliability and validity; however, there were significant cross-loadings that have been discussed in detail in the succeeding text. Further, this is the first study in the Arab world that uses exploratory structural equation modelling and build a hierarchical structure to investigate the PID-5. © 2020 John Wiley & Sons, Ltd.

Genotype-Environment Correlation and Its Relation to Personality - A Twin and Family Study

The aim of the study was to examine the Family and School Psychosocial Environment (FSPE) questionnaire in relation to a possible genotype-environment correlation and genetic mediation between the FSPE variables and personality variables, assessed by the Junior Eysenck Personality Questionnaire. A sample of 506 Swedish children aged 10-20 years from 253 families were recruited via the Swedish state population and address register and SchoolList.Eu. The children were divided into 253 pairs: 46 monozygotic twin pairs, 42 dizygotic twin pairs, 140 pairs of full siblings and 25 pairs of half-siblings. The behavioral genetic analysis showed that both FSPE factors, Warmth and Conflicts, may be partly influenced by genetic factors (suggesting genotype-environment correlation) and that nonadditive genetic factors may mediate the relationship between FSPE factors and psychoticism/antisocial personality (P). An indication of a special shared monozygotic twin environment was found for P and Lie/social desirability, but based on prior research findings this factor may have a minor influence on P and L. P and L were negatively correlated, and the relationship seems to be partly mediated by nonadditive genetic factors. Nonshared environment and measurement errors seem to be the most influential mediating factors, but none of the cross-twin cross-dimension correlations suggest a common shared environmental mediating factor.

Single nucleotide polymorphism heritability and differential patterns of genetic overlap between inattention and four neurocognitive factors in youth

Theoretical models of attention-deficit/hyperactivity disorder implicate neurocognitive dysfunction, yet neurocognitive functioning covers a range of abilities that may not all be linked with inattention. This study (a) investigated the single nucleotide polymorphism (SNP) heritability (h2SNP) of inattention and aspects of neurocognitive efficiency (memory, social cognition, executive function, and complex cognition) based on additive genome-wide effects; (b) examined if there were shared genetic effects among inattention and each aspect of neurocognitive efficiency; and (c) conducted an exploratory genome-wide association study to identify genetic regions associated with inattention. The sample included 3,563 participants of the Philadelphia Neurodevelopmental Cohort, a general population sample aged 8-21 years who completed the Penn Neurocognitive Battery. Data on inattention was obtained with the Kiddie Schedule of Affective Disorders (adapted). Genomic relatedness matrix restricted maximum likelihood was implemented in genome-wide complex trait analysis. Analyses revealed significant h2SNP for inattention (20%, SE = 0.08), social cognition (13%, SE = 0.08), memory (17%, SE = 0.08), executive function (25%, SE = 0.08), and complex cognition (24%, SE = 0.08). There was a positive genetic correlation (0.67, SE = 0.37) and a negative residual covariance (-0.23, SE = 0.06) between inattention and social cognition. No SNPs reached genome-wide significance for inattention. Results suggest specificity in genetic overlap among inattention and different aspects of neurocognitive efficiency.

Hair Cortisol in Twins: Heritability and Genetic Overlap with Psychological Variables and Stress-System Genes

Hair cortisol concentration (HCC) is a promising measure of long-term hypothalamus-pituitary-adrenal (HPA) axis activity. Previous research has suggested an association between HCC and psychological variables, and initial studies of inter-individual variance in HCC have implicated genetic factors. However, whether HCC and psychological variables share genetic risk factors remains unclear. The aims of the present twin study were to: (i) assess the heritability of HCC; (ii) estimate the phenotypic and genetic correlation between HPA axis activity and the psychological variables perceived stress, depressive symptoms, and neuroticism; using formal genetic twin models and molecular genetic methods, i.e. polygenic risk scores (PRS). HCC was measured in 671 adolescents and young adults. These included 115 monozygotic and 183 dizygotic twin-pairs. For 432 subjects PRS scores for plasma cortisol, major depression, and neuroticism were calculated using data from large genome wide association studies. The twin model revealed a heritability for HCC of 72%. No significant phenotypic or genetic correlation was found between HCC and the three psychological variables of interest. PRS did not explain variance in HCC. The present data suggest that HCC is highly heritable. However, the data do not support a strong biological link between HCC and any of the investigated psychological variables.

Multivariate genetic analyses in heterogeneous populations

Martin and Eaves (Heredity 38(1):79-95, 1977) proposed a multivariate model for twin and family data in order to investigate potential differences in the genetic and environmental architecture of multivariate phenotypes. The general form of the model is the independent pathway model, which differentiates between genetic and environmental influences at the item level, and therefore permits the decomposition to differ across items. A restricted version is the common pathway model, where the decomposition takes place at the factor level. The paper has spurred numerous studies, and evidence for differences in genetic and environmental architecture has been established for personality and several other psychiatric phenotypes by showing a better fit of the independent pathway model compared to the common pathway model. We show that genome-wide association studies (GWAS) that use an aggregate score computed from multiple questionnaire items as a univariate phenotype implicitly assume a similar structure as the common pathway model. It has been shown that in case of a differential genetic and environmental architecture, multivariate GWAS methods can outperform the univariate GWAS approach. However, current multivariate methods rely on the assumptions of phenotypic and genetic homogeneity, that is, item responses are assumed to have the same means and covariances, and genetic effects are assumed to be the same for all subjects. We describe a distance-based regression technique that is designed to account for subgroups in the population, and that therefore can account for differential genetic effects. A first evaluation with simulated data shows a substantial increase of power compared to univariate GWAS.

A questionnaire-wide association study of personality and mortality: the Vietnam Experience Study

OBJECTIVE

We examined the association between the Minnesota Multiphasic Personality Inventory (MMPI) and all-cause mortality in 4462 middle-aged Vietnam-era veterans.

METHODS

We split the study population into half-samples. In each half, we used proportional hazards (Cox) regression to test the 550 MMPI items' associations with mortality over 15years. In all participants, we subjected significant (p<.01) items in both halves to principal-components analysis (PCA). We used Cox regression to test whether these components predicted mortality when controlling for other predictors (demographics, cognitive ability, health behaviors, and mental/physical health).

RESULTS

Eighty-nine items were associated with mortality in both half-samples. PCA revealed Neuroticism/Negative Affectivity, Somatic Complaints, Psychotic/Paranoia, and Antisocial components, and a higher-order component, Personal Disturbance. Individually, Neuroticism/Negative Affectivity (HR=1.55; 95% CI=1.39, 1.72), Somatic Complaints (HR=1.66; 95% CI=1.52, 1.80), Psychotic/Paranoid (HR=1.44; 95% CI=1.32, 1.57), Antisocial (HR=1.79; 95% CI=1.59, 2.01), and Personal Disturbance (HR=1.74; 95% CI=1.58, 1.91) were associated with risk. Including covariates attenuated these associations (28.4 to 54.5%), though they were still significant. After entering Personal Disturbance into models with each component, Neuroticism/Negative Affectivity and Somatic Complaints were significant, although Neuroticism/Negative Affectivity's were now protective (HR=0.73; 95% CI=0.58, 0.92). When the four components were entered together with or without covariates, Somatic Complaints and Antisocial were significant risk factors.

CONCLUSIONS

Somatic Complaints and Personal Disturbance are associated with increased mortality risk. Other components' effects varied as a function of variables in the model.

Multivariate genetic analysis of learning and early reading development

The genetic factor structure of a range of learning measures was explored in twin children, recruited in preschool and followed to Grade 2 (total N = 2084). Measures of orthographic learning and word reading were included in the analyses to determine how these patterned with the learning processes. An exploratory factor analysis of the genetic correlations among the variables indicated a three-factor model. Vocabulary tests loaded on the first factor, the Grade 2 measures of word reading and orthographic learning, plus preschool letter knowledge, loaded on the second, and the third was characterized by tests of verbal short-term memory. The three genetic factors correlated, with the second (print) factor showing the most specificity. We conclude that genetically-influenced learning processes underlying print-speech integration, foreshadowed by preschool letter knowledge, have a degree of independence from genetic factors affecting spoken language. We also argue that the psychology and genetics of associative learning be afforded a more central place in studies of reading (dis)ability, and suggest some links to molecular studies of the genetics of learning.

Broad bandwidth or high fidelity? Evidence from the structure of genetic and environmental effects on the facets of the five factor model

The Five Factor Model of personality is well-established at the phenotypic level, but much less is known about the coherence of the genetic and environmental influences within each personality domain. Univariate behavioral genetic analyses have consistently found the influence of additive genes and nonshared environment on multiple personality facets, but the extent to which genetic and environmental influences on specific facets reflect more general influences on higher order factors is less clear. We applied a multivariate quantitative-genetic approach to scores on the CPI-Big Five facets for 490 monozygotic and 317 dizygotic twins who took part in the National Merit Twin Study. Our results revealed a complex genetic structure for facets composing all five factors, with both domain-general and facet-specific genetic and environmental influences. For three of the Big Five domains, models that required common genetic and environmental influences on each facet to occur by way of effects on a higher order trait did not fit as well as models allowing for common genetic and environmental effects to act directly on the facets. These results add to the growing body of literature indicating that important variation in personality occurs at the facet level which may be overshadowed by aggregating to the trait level. Research at the facet level, rather than the factor level, is likely to have pragmatic advantages in future research on the genetics of personality.

Genetic and environmental influences on impulsivity: a meta-analysis of twin, family and adoption studies

A meta-analysis of twin, family and adoption studies was conducted to estimate the magnitude of genetic and environmental influences on impulsivity. The best fitting model for 41 key studies (58 independent samples from 14 month old infants to adults; N=27,147) included equal proportions of variance due to genetic (0.50) and non-shared environmental (0.50) influences, with genetic effects being both additive (0.38) and non-additive (0.12). Shared environmental effects were unimportant in explaining individual differences in impulsivity. Age, sex, and study design (twin vs. adoption) were all significant moderators of the magnitude of genetic and environmental influences on impulsivity. The relative contribution of genetic effects (broad sense heritability) and unique environmental effects were also found to be important throughout development from childhood to adulthood. Total genetic effects were found to be important for all ages, but appeared to be strongest in children. Analyses also demonstrated that genetic effects appeared to be stronger in males than in females. Method of assessment (laboratory tasks vs. questionnaires), however, was not a significant moderator of the genetic and environmental influences on impulsivity. These results provide a structured synthesis of existing behavior genetic studies on impulsivity by providing a clearer understanding of the relative genetic and environmental contributions in impulsive traits through various stages of development.

Development of polytoxicomania in function of defence from psychoticism

INTRODUCTION

Polytoxicomanic proportions in subpopulations of youth have been growing steadily in recent decades, and this trend is pan-continental. Psychoticism is a psychological construct that assumes special basic dimensions of personality disintegration and cognitive functions. Psychoticism may, in general, be the basis of pathological functioning of youth and influence the patterns of thought, feelings and actions that cause dysfunction.

OBJECTIVE

The aim of this study was to determine the distribution of basic dimensions of psychoticism for commitment of youth to abuse psychoactive substances (PAS) in order to reduce disturbing intrapsychic experiences or manifestation of psychotic symptoms.

METHODS

For the purpose of this study, two groups of respondents were formed, balanced by age, gender and family structure of origin (at least one parent alive). The study applied a DELTA-9 instrument for assessment of cognitive disintegration in function of establishing psychoticism and its operationalization. The obtained results were statistically analyzed. From the parameters of descriptive statistics, the arithmetic mean was calculated with measures of dispersion. A cross-tabular analysis of variables tested was performed, as well as statistical significance with Pearson's chi2-test, and analysis of variance.

RESULTS

Age structure and gender are approximately represented in the group of polytoximaniacs and the control group. Testing did not confirm the statistically significant difference (p > 0.5). Statistical methodology established that they significantly differed in most variables of psychoticism, polytoxicomaniacs compared with a control group of respondents. Testing confirmed a high statistical significance of differences of variables of psychoticism in the group of respondents for p < 0.001 to p < 0.01.

CONCLUSION

A statistically significant representation of the dimension of psychoticism in the polytoxicomaniac group was established. The presence of factors concerning common executive dysfunction was emphasized.

Genetic and environmental influences on externalizing behavior and alcohol problems in adolescence: a female twin study

Genetic and environmental contributions to the observed correlations among DSM-IV ADHD problems [inattentive (INATT) and hyperactive/impulsive (HYP/IMP) behaviors], conduct problems (CDP) and alcohol problems (AlcProb) were examined by fitting multivariate structural equation models to data from the Missouri Adolescent Female Twin Study [N=2892 twins (831 monozygotic pairs, 615 dizygotic pairs)]. Based on results of preliminary regression models, we modified the structural model to jointly estimate (i) the regression of each phenotype on significant familial/prenatal predictors, and (ii) genetic and environmental contributions to the residual variance and covariance. Results suggested that (i) parental risk factors, such as parental alcohol dependence and regular smoking, increase risk for externalizing behavior; (ii) prenatal exposures predicted increased symptomatology for HYP/IMP (smoking during pregnancy), INATT and CDP (prenatal alcohol exposure); (iii) after adjusting for measured familial/prenatal risk factors, genetic influences were significant for HYP/IMP, INATT, and CDP; however, similar to earlier reports, genetic effects on alcohol dependence symptoms were negligible; and (iv) in adolescence, correlated liabilities for conduct and alcohol problems are found in environmental factors common to both phenotypes, while covariation among impulsivity, inattention, and conduct problems is primarily due to genetic influences common to these three behaviors. Thus, while a variety of adolescent problem behaviors are significantly correlated, the structure of that association may differ as a function of phenotype (e.g., comorbid HYP/IMP and CDP vs. comorbid CDP and AlcProb), a finding that could inform different approaches to treatment and prevention.

A genome-wide scan for Eysenckian personality dimensions in adolescent twin sibships: psychoticism, extraversion, neuroticism, and lie

We report the first genome-wide scan of adolescent personality. We conducted a genome-wide scan to detect linkage for measures of adolescent Psychoticism, Extraversion, Neuroticism, and Lie from the Junior Eysenck Personality Questionnaire. Data are based on 1,280 genotyped Australian adolescent twins and their siblings. The highest linkage peaks were found on chromosomes 16 and 19 for Neuroticism, on chromosomes 1, 7, 10, 13 m, and 18 for Psychoticism, and on chromosomes 2 and 3 for Extraversion.

The Behavioral Genetics of Personality Disorder

Behavioral genetics research has opened a new window on understanding personality disorder. The earliest studies were focused on establishing the relative contributions of genes and the environment in these disorders. Although these studies provided solid evidence of the importance of genetic and environmental influences on personality disorder and showed that all aspects of personality disorder are subject to genetic influence, heritability studies are limited because they are not helpful in explicating causal mechanisms. More recent research has focused on the relative contributions of the covariation of personality disorder diagnoses and traits, which allows one to examine etiological relationships. These developments are leading to major changes in ideas about what constitutes the environment and nature of the interplay between genes and environment. The present review examines major themes in this growing body of research in the context of current issues in the personality disorders.

Genetic and environmental influences on extreme personality dispositions in adolescent female twins

BACKGROUND

The objective was to determine whether the pattern of environmental and genetic influences on deviant personality scores differs from that observed for the normative range of personality, comparing results in adolescent and adult female twins.

METHODS

A sample of 2,796 female adolescent twins ascertained from birth records provided Junior Eysenck Personality Questionnaire data. The average age of the sample was 17.0 years (S.D. 2.3). Genetic analyses of continuous and extreme personality scores were conducted. Results were compared for 3,178 adult female twins.

RESULTS

Genetic analysis of continuous traits in adolescent female twins were similar to findings in adult female twins, with genetic influences accounting for between 37% and 44% of the variance in Extraversion (Ex), Neuroticism (N), and Social Non-Conformity (SNC), with significant evidence of shared environmental influences (19%) found only for SNC in the adult female twins. Analyses of extreme personality characteristics, defined categorically, in the adolescent data and replicated in the adult female data, yielded estimates for high N and high SNC that deviated substantially (p < .05) from those obtained in the continuous trait analyses, and provided suggestive evidence that shared family environment may play a more important role in determining personality deviance than has been previously found when personality is viewed continuously. However, multiple-threshold models that assumed the same genetic and environmental determinants of both normative range variation and extreme scores gave acceptable fits for each personality dimension.

CONCLUSIONS

The hypothesis of differences in genetic or environmental factors responsible for N and SNC among female twins with scores in the extreme versus normative ranges was partially supported, but not for Ex.

Temperament characteristics, as assessed by the tridimensional personality questionnaire, moderate the response to sertraline in depressed opiate-dependent methadone patients

During a randomized, double-blind, placebo controlled study of the effects of sertraline in depressed methadone-maintained patients, 82 completed the tridimensional personality questionnaire (TPQ) to assess whether temperament dimensions can affect treatment-related changes in mood and drug use. Mood outcome significantly differed according to scores on the reward dependence scale (RD). Low RD participants displayed a significantly better mood response to sertraline than high RD participants. Participants with high harm avoidance (HA) scores were more likely to be abstinent at the end of the 12 week trial of sertraline than low HA participants. High persistence (P) participants were less likely to be abstinent at the end of the 12-week trial. These results suggest that temperament dimensions may be important for identifying substance dependent patients more likely to benefit from pharmacological interventions for comorbid depressive disorders.

Behavioral and molecular genetic contributions to a dimensional classification of personality disorder

This article examines the possible contribution of behavioral and molecular genetic research to the development of a dimensional classification of personality disorder. It is argued that the results of molecular studies are too preliminary to have immediate nosological significance. However, behavioral genetic methods could play a useful role in constructing a classification that reflects the genetic architecture of personality disorder. It is also argued that the best approach to constructing a valid classification would be to integrate behavioral genetic methods with the construct validation framework used in test construction. An integrative approach is proposed that seeks to combine constructs from alternative dimensional models. It is suggested that strong evidence of a four-dimensional structure to personality disorder provides a way to organize a preliminary model. An initial set of primary traits to define these secondary domains would then be compiled from existing models and refined using a combination of traditional psychometric analyses and behavioral genetic methods. It is concluded that an etiologically based classification is feasible for the DSM-V.

Neuroticism: a non-informative marker of vulnerability to psychopathology

BACKGROUND

Neuroticism measures are very popular in psychopathological research, but it is unclear how useful neuroticism is in studies of the aetiology of psychopathology.

METHOD

A conceptual examination was made of the literature on the association of neuroticism and psychopathology, the ontological status of neuroticism, the purport of neuroticism questionnaires, and causal issues.

RESULTS

The research on which neuroticism is built has historically been based solely on the factor analyses of the common adjectives used to describe usual behaviours. An abundance of studies have shown that neuroticism scores predict life stress, psychological distress, emotional disorders, psychotic symptoms, substance abuse, physical tension-related symptoms, medically unexplained physical symptoms, and health care utilisation. This evidence suggests that neuroticism scales index vulnerability to many forms of negative affect and psychiatric disorder. However, the associations do not clarify the nature of this vulnerability nor the underlying psychobiological mechanisms. We present evidence that neuroticism scores reflect a person's characteristic (or mean) level of distress over a protracted period of time. In this perspective, even prospective associations of neuroticism with mental health outcomes are basically futile, and largely tautological since scores on any characteristic with substantial within-subject stability will predict, by definition, that characteristic and related variables at later points in time.

CONCLUSION

Neuroticism is not an explanatory concept in the aetiology of psychopathology, since it measures a person's characteristic level of distress over a protracted period of time. This situation will not change until knowledge becomes available about: (i) the mechanisms that produce high neuroticism scores (and, therefore, also psychopathology) and (ii) its neurobiological substrate. Only then will we understand why neuroticism appears to "predict" the outcomes it predicts.

Genetic and environmental influences on human psychological differences

Psychological researchers typically distinguish five major domains of individual differences in human behavior: cognitive abilities, personality, social attitudes, psychological interests, and psychopathology (Lubinski, 2000). In this article we: discuss a number of methodological errors commonly found in research on human individual differences; introduce a broad framework for interpreting findings from contemporary behavioral genetic studies; briefly outline the basic quantitative methods used in human behavioral genetic research; review the major criticisms of behavior genetic designs, with particular emphasis on the twin and adoption methods; describe the major or dominant theoretical scheme in each domain; and review behavioral genetic findings in all five domains. We conclude that there is now strong evidence that virtually all individual psychological differences, when reliably measured, are moderately to substantially heritable.

Zur deutschsprachigen Version des Temperament- und Charakterinventars

Zusammenfassung. Es erfolgt eine kurze zusammenfassende Darstellung des theoretischen Hintergrundes und der Dimensionen des Temperament- und Charakterinventars (TCI). - Die Kennwerte für die interne Konsistenz anhand einer deutschen Normstichprobe von 509 gesunden Freiwilligen und für die Stabilität anhand einer Stichprobe von 75 stationären Patienten für den Behandlungsverlauf werden sowohl für die Dimensionen als auch für die Subskalen dargestellt. Erste Hinweise auf die Validität des Verfahrens in deutschen Stichproben werden in Form von Korrelationen mit den Faktoren des EMBU-Fragebogens, einem Verfahren zur Erfassung des erlebten elterlichen Erziehungsverhaltens, berichtet. Die interne Konsistenz für die Dimensionen “Beharrungsvermögen” und “Belohnungsabhängigkeit” entsprechen noch nicht den Erwartungen. Das Verfahren befindet sich aber international noch in der Entwicklung.

Genetic and environmental variation in Eysenck Personality Questionnaire scales measured on Australian adolescent twins

The Eysenck Personality Questionnaire was administered to 1400 Australian twin pairs aged 11 to 18, and the data were analyzed by a multivariate normal model using the software FISHER. For each scale, attempts were made to transform to normality, about a mean modeled separately for each sex as a quadratic function of age. Variances and covariances were estimated for each sex-zygosity group as a monotone function of age. Evidence for genetic sources of variation were assessed in part by fitting models which allowed for age-dependent, sex-specific, and correlated additive genetic factors, and age-dependent and sex-specific environmental factors, under the assumption that effects of environmental factors common to twin pairs are independent of zygosity. Evidence for genetic factors independent of age and sex was most compelling for Psychoticism and Neuroticism. For Extraversion, if genetic factors exist they would be mostly sex-specific and age-dependent. For the Lie scale there was evidence for, at most, a small component of genetic variation.

Personality is indeterminate

The so-called unique environmental factor in behaviour genetics research, the longitudinal instability of personality, and the unpredictability of human creativity are all manifestations of the same process. Thus a scientific explanation of any one of them should account for them all. That process, it is proposed, is the inherently indeterminate global dynamics of the human brain. The clear implication is that all social sciences have inherently indeterminate phenomena as their subject matter. Predictions of the results of an appropriately designed psychometric study based on this hypothesis are offered.

Brain, environment, heredity, and personality

Behavior genetics research, committed to a model of the origins of personality and intellectual development restricted to heredity and environment, consistently generates evidence for two types of environmental influences. One of these, termed the between-family or shared environment, creates no conceptual problems. The other, termed the nonshared or within-family or unique environment, does. The other, termed the nonshared or within-family or unique environment, does. The latter accounts for a substantial portion of the variance in personality and intellect, it must be unique to each individual, and its origin has not been determined. It is contended here that the brain itself, as an inherently indeterminate dynamic system, is the source of this unresolved developmental variability.

Parent-offspring and sibling adoption analyses of parental ratings of temperament in infancy and childhood

A first step toward understanding the etiology of personality is to investigate the relative impact of genetic and environmental factors using twin and adoption designs. Twin studies of infants and young children indicate substantial genetic influence for parental ratings of temperament in the preschool years. Adoption studies, however, have not previously been reported during the early years of life. We present parent-offspring comparisons for temperament (emotionality, activity, sociability, and impulsivity) for adopted and nonadopted children yearly from 1 to 7 years of age and their biological, adoptive, and nonadoptive parents. Also presented are correlations for adoptive and nonadoptive siblings when each child was 1, 2, 3, and 4 years of age. In contrast with twin results, little evidence is found for genetic influence. The average correlation between biological parents and their adopted-away children for data averaged over the 7 years is only .03. Similarly, the average parent-offspring correlation in nonadoptive families (.08) is no greater than in adoptive families (.12). Results for nonadoptive and adoptive siblings also indicate little genetic influence. The difference between the twin and adoption results may be due to environmental effects or to nonadditive genetic variance.

Developmental, structural, and clinical approach to narcissistic and antisocial personalities

The conception of personality disorders (PDs) as distinct units of mental disorders is neither precise nor useful. At least some PDs, classified as separate units, reflect different behavioral expression of the same personality deviation. In this article we describe structural, developmental, and clinical continuum between relatively distinct entities of antisocial PD and narcissistic PD. The two disorders represent different endpoints sharing a borderline level of personality organization and pathological narcissism. We propose a spectrum relation for antisocial and narcissistic PD because the disorders tend to co-occur in the same individual and to run in the same family more often than expected by chance.

Further contribution to the conceptual validity of the unified biosocial model of personality: US and Yugoslav data

In this study, the conceptual validity of the unified model of personality, postulated by Cloninger (1987) and measured by the Tridimensional Personality Questionnaire (TPQ), is tested in diverse Yugoslav and American societies. The issue of cross-cultural sensitivity of personality studies and the methodology that minimizes distortions and alternative explanations are discussed in detail. Similar personality structures were observed in the Yugoslav and US samples. Differences in novelty seeking (NS, attributed to age differences between the two samples) and harm avoidance (HA, possibly due to long-standing socioeconomic instability in Yugoslavia) are consistent with the unified biosocial theory of personality. Also, the TPQ was found to be psychometrically sound and valid for further research, although some revision in the reward dependence (RD) scale is warranted.

Sexual orientation, sexual identity, and sex-dimorphic behaviors in male twins

Sexual orientation, sexual identity, and sex-dimorphic behaviors were assessed concurrently and retrospectively, for childhood, in 95 pairs of male monozygotic (MZ) twins and 63 pairs of dizygotic (DZ) twins. There was a significantly higher rate of adult homosexuality among the MZ than among DZ twins. We employed a model-fitting approach using LISREL to test for genetic and environmental influences on variation for each trait singly and on the covariation among all six traits (three for childhood and three for adulthood). Univariate analyses confirmed the presence of familial factors for five of the six variables but were generally unable to distinguish shared environmental from genetic influences. Hierarchical tests of multivariate models supported the existence of an additive genetic factor contributing to the covariance among the variables. More restrictive multivariate models yielded a significant genetic influence on sexual orientation. Because of the different rates of orientation by zygosity and because of the restrictive nature of some of the multivariate models, our results are best considered tentative but do suggest that further biometrically oriented studies of sexual orientation and its correlates would be worthwhile.