Personality Dimensions as Common and Broadband-Specific Features for Internalizing and Externalizing Disorders

Several researchers have suggested that the nature of the covariation between internalizing and externalizing disorders may be understood better by examining the associations between temperament or personality and these disorders. The present study examined neuroticism as a potential common feature underlying both internalizing and externalizing disorders and novelty seeking as a potential broad-band specific feature influencing externalizing disorders alone. Participants were 12- to 18-year-old twin pairs (635 monozygotic twin pairs and 691 dizygotic twin pairs; 48 % male and 52 % female) recruited from the Colorado Center for Antisocial Drug Dependence. Genetic and nonshared environmental influences shared in common with neuroticism influenced the covariation among distinct internalizing disorders, the covariation among distinct externalizing disorders, and the covariation between internalizing and externalizing disorders. Genetic influences shared in common with novelty seeking influenced the covariation among externalizing disorders and the covariation between major depressive disorder and externalizing disorders, but not the covariation among internalizing disorders or between anxiety disorders and externalizing disorders. Also, after accounting for genetic and environmental influences shared in common with neuroticism and novelty seeking, there were no significant common genetic or environmental influences among the disorders examined, suggesting that the covariance among the disorders is sufficiently explained by neuroticism and novelty seeking. We conclude that neuroticism is a heritable common feature of both internalizing disorders and externalizing disorders, and that novelty seeking is a heritable broad-band specific factor that distinguishes anxiety disorders from externalizing disorders.     

Genetic and environmental influences on antisocial behavior: a meta-analysis of twin and adoption studies

A meta-analysis of 51 twin and adoption studies was conducted to estimate the magnitude of genetic and environmental influences on antisocial behavior. The best fitting model included moderate proportions of variance due to additive genetic influences (.32), nonadditive genetic influences (.09), shared environmental influences (.16), and nonshared environmental influences (.43). The magnitude of familial influences (i.e., both genetic and shared environmental influences) was lower in parent-offspring adoption studies than in both twin studies and sibling adoption studies. Operationalization, assessment method, zygosity determination method, and age were significant moderators of the magnitude of genetic and environmental influences on antisocial behavior, but there were no significant differences in the magnitude of genetic and environmental influences for males and females.     

Neuroticism and Morning Cortisol Secretion: Both Heritable, But No Shared Genetic Influences

ABSTRACT Neuroticism is widely used as an explanatory concept in etiological research of psychopathology. To clarify what neuroticism actually represents, we investigated the phenotypic and genetic relationship between neuroticism and the morning cortisol secretion. In the current classic twin study, 125 female twin pairs (74 monozygotic and 51 dizygotic pairs) participated. For each participant, 4 different neuroticism scores were available to calculate a neuroticism composite score that was used in the statistical analyses. The morning cortisol secretion was assessed by 4 salivary samples in the 1st hour after awakening. Significant genetic influences for the neuroticism composite score (55%), and each of the 4 cortisol samples (52%–69%) were found. There was no phenotypic or genotypic relationship between neuroticism and morning cortisol secretion. Although neuroticism and cortisol were both heritable traits, they did not share any genetic influences.     

Genetic and Environmental Pathways Underlying Personality Traits and Perceived Stress: Concurrent and Longitudinal Twin Studies

The present study examined the genetic and environmental etiology underlying the Big Five personality traits and perceived stress, concurrently and longitudinally. In study 1, we used the twin sample from the National Longitudinal Study of Adolescent to Adult Health (Add Health IV) data. The results indicated that about 70% of the association between the Big Five personality traits and perceived stress was due to genetic influences. In study 2, we used the twin sample from the Midlife in the United States Survey (MIDUS I and II) to examine the genetic and environmental influences underlying the longitudinal relations between the Big Five personality traits and perceived stress. The results suggested that continuity in perceived stress was primarily accounted for by genetic influences, and changes in perceived stress were mainly due to nonshared environmental influences. The continuity in the association between the five personality traits and perceived stress was largely accounted for by genetic factors, and nonshared environmental factors made greater contributions to changes in the association between personality traits and perceived stress. Among the Big Five personality traits, the genetic components in conscientiousness and neuroticism made substantial contributions to the genetic link between personality traits and perceived stress across both studies. Copyright © 2017 European Association of Personality Psychology     

Genetic and behavioral risk factors for self-reported joint pain among a population-based sample of Swedish twins.

Self-reported joint pain, a typical manifestation of osteoarthritis, was examined using 335 twin pairs from the Swedish Adoption/Twin Study of Aging to estimate relative genetic and environmental influences on self-reported joint pain and to examine the relationships between joint pain, health behavior, and psychological variables. Findings suggest that family resemblance for self-reported joint pain represents similar environments more than genetic similarity. Data from the early 1970s, including exercise, physical activity at work, obesity, and neuroticism, were used to predict joint pain in 1993. For men, moderate amounts of exercise decreased the likelihood of joint pain, but strenuous amounts of physical activity in the workplace had the opposite effect. For women, exercise and physical activity were not significant predictors, but past obesity and higher levels of neuroticism increased the likelihood of reporting joint pain in 1993.     

Physical activity and personality: A behaviour genetic analysis

ObjectivesThe aim of this study was to obtain a heritability estimate of exercise behaviour in twins and to examine the genetic and environmental contributions to phenotypic associations between personality and exercise behaviour.DesignTwin study was used, the sample including 339 twin pairs (105 MZ and 234 DZ), between 15 and 22 years of age (M = 18.6, SD = 2.31).MethodThe participants filled in a NEO-FFI personality inventory and answered two questions about the frequency (FPE) and intensity (IPE) of physical exercise. We also calculated the composite physical exercise score (CS) representing a combination of FPE and IPE items.ResultsThe broad heritability estimates of three physical exercise variables (FPE, IPE, CS) were significant, with results in the 0.55 to 0.69 range. We found significant phenotypic associations with neuroticism and extraversion. Contrary to our expectations, correlations with conscientiousness were not significant. People scoring higher on extraversion and lower on neuroticism reported exercising more often and more intensely. Phenotypic association between personality traits and physical exercise variables were due to overlapping genetic influences.ConclusionsOur results indicate that the genetic factors contributing to an active lifestyle overlap with those contributing to personality traits extraversion and neuroticism, in line with the “nature” hypothesis which infers the presence of biological differences in predisposition for regular physical activity.     

Why do measures of normal and disordered personality correlate? A study of genetic comorbidity

The genetic and environmental correlations between measures of normal (NEO-FFI) and abnormal personality (Dimensional Assessment of Personality Pathology: DAPP-BQ) were estimated in a sample of 545 volunteer general population twin pairs (269 monozygotic and 276 dizygotic pairs). The largest genetic correlations were observed between the 18 DAPP-BQ dimensions and NEO-FFI neuroticism (range = .05 to .81; median = .48), extraversion (range = -.65 to .33; median = -.28), agreeableness (range = -.65 to .00; median = -.38), and conscientiousness (range = -.76 to .52; median = -.31). The smallest genetic correlations were found between the DAPP-BQ dimensions and NEO-FFI openness (range = -.17 to .20; median = -.04). The environmental correlations are lower in magnitude but show the same pattern of correlations between DAPP-BQ and NEO-FFI scales. These results indicate that these two scales share a common broad-based genetic architecture, whereas the environmental influences show greater scale specificity.     

Child and adolescent conduct disorder substantially shares genetic influences with three socioemotional dispositions

In a representative sample of twin children and adolescents, we tested the hypothesis that a substantial proportion of the genetic and environmental influences underlying conduct disorder (CD) are shared with three socioemotional dispositions: Prosociality, Negative Emotionality, and Daring. Caretaker ratings of each dispositional dimension were uniquely associated with a latent CD dimension that included both caretaker- and youth-reports of CD as indicators. Behavior genetic analyses indicated that moderate-to-high additive genetic and moderate nonshared environmental influences underlie all three dispositions and CD, with modest shared environmental influences on Prosociality. Forty percent of the additive genetic influences and all of the nonshared environmental influences on the latent CD dimension were shared in common with the three socioemotional dispositions. The finding that CD shares a substantial proportion of its genetic influences with three distinct socioemotional dispositions suggests new perspectives on the heterogeneous etiology of CD and new approaches to exploring its specific etiological mechanisms.     

Common Etiological Sources of Anxiety,Depression, and Somatic Complaints in Adolescents: A Multiple Rater twin Study

Somatic complaints in children and adolescents may be considered part of a broader spectrum of internalizing disorders that include anxiety and depression. Previous research on the topic has focused mainly on the relationship between anxiety and depression without investigating how common somatic symptoms relate to an underlying factor and its etiology. Based on the classical twin design with monozygotic and dizygotic twins reared together, our study aimed to explore the extent to which the covariation between three phenotypes in adolescent girls and boys can be represented by a latent internalizing factor, with a focus on both common and specific etiological sources. A population-based sample of twins aged 12–18 years and their mothers and fathers (N?=?1394 families) responded to questionnaire items measuring the three phenotypes. Informants’ ratings were collapsed using full information maximum likelihood estimated factor scores. Multivariate genetic analyses were conducted to examine the etiological structure of concurrent symptoms. The best fitting model was an ACE common pathway model without sex limitation and with one substantially heritable (44 %) latent factor shared by the phenotypes. Concurrent symptoms also resulted from shared (25 %) and non-shared (31 %) environments. The factor loaded most on depression symptoms and least on somatic complaints. Trait-specific influences explained 44 % of depression variance, 59 % of anxiety variance, and 65 % of somatic variance. Our results suggest the presence of a general internalizing factor along which somatic complaints and mental distress can be modeled. However, specific influences make the symptom types distinguishable.     

Executive self, self-esteem, and negative affectivity: relations at the phenotypic and genotypic level

Complementary approaches examined the relations among executive self, self-esteem, and negative affectivity. A cross-sectional (N = 4,242) and a longitudinal (N = 158) study established that self-esteem mediated the relation between executive self and negative affectivity. A 3rd study (N = 878 twin pairs) replicated this pattern and examined genetic and environmental influences underlying all 3 phenotypes. Covariation among the 3 phenotypes reflected largely common genetic influences, although unique genetic effects explained variability in both executive self and negative affectivity. Executive self was influenced by shared environmental influences unique from those affecting self-esteem and negative affectivity. Non-shared environmental influences accounted for the majority of variance in each construct and were primarily unique to each. The unique genetic and non-shared environmental influences support the proposition that the executive self, self-esteem, and negative affectivity capture distinct and important differences between people.     

Genetic and environmental influences on individual differences in masculinity, femininity, and gender diagnosticity: analyzing data from a classic twin study

Analyzing data from Loehlin and Nichols's (1976) classic twin study, we computed measures of Masculine Instrumentality (M), Feminine Expressiveness (F), and Gender Diagnosticity (GD). Quantitative genetic modeling analyses of within-sex individual differences in M, F, and GD indicated that: (1) Additive genetic factors contribute significantly to individual differences in M, F, and GD. (2) The environmental effects on M, F, and GD tend to be nonshared. (3) The genetic and environmental components of individual differences in M, F, and GD tend not to show gender differences. Finally, (4) the estimated within-sex heritability of GD (.53) is significantly greater than the estimated within-sex heritabilities of either M (.36) or F (.38).     

A Twin Study of the Relationships among Inattention, Hyperactivity/Impulsivity and Sluggish Cognitive Tempo Problems

We investigated the etiological relationships between the three ADHD dimensions of Inattentive Problems (INP), Hyperactivity-Impulsivity Problems (HIP) and Sluggish Cognitive Tempo (SCT) as measured by the CBCL 6–18 questionnaire. Multivariate models were applied to 398 twin pairs (374 boys and 422 girls) aged 8 to 17 years (M?=?13.06, SD?=?2.59) belonging to the population-based Italian Twin Registry. The INP, HIP and SCT problem scores were moderately-to-substantially (range 0.29–0.47) intercorrelated. The best fitting model showed that these 3 dimensions are correlated both at the genetic (correlations’ range: 0.65–0.83) and the environmental (correlations: 0.29 and 0.44) levels, but they are also distinct. While SCT showed moderate heritability and large non-shared environmental influences, variance for both INP and HIP was substantially explained by genetic influences. We also found evidence of negative sibling interaction for INP, implying that a given behavior in one twin leads to an opposite behavior in the co-twin. Our results support at the etiological level the findings of previous psychometric and longitudinal studies of ADHD, which yielded evidence of the 3 distinct—albeit correlated—problem dimensions of inattentiveness, hyperactivity-impulsivity, and sluggish cognitive tempo.     

Stability and change in genetic and environmental components of personality in old age

Stability and change in the mean levels and sources of variation in personality was examined. A sample of 149 monozygotic and 202 dizygotic twin pairs over 80 years were studied three times with a 2-year interval between measurement occasions. The Eysenck Personality Inventory to measure extraversion and neuroticism was used. Linear mixed models and Cholesky variance decomposition were carried out (age, gender and mortality controlled). High mean level stability was found in extraversion and neuroticism. Mortality was related to lower scores in extraversion and higher scores in neuroticism. In extraversion and neuroticism, genetic effects were moderate. Though no new genetic contributions emerged over time, significant new environmental effects were found over time. Controlling for mortality slightly increased genetic effect in extraversion.     

Psychological and Somatic Factors in Patients Undergoing Coronary Artery Bypass Graft Surgery: Towards Building a Psychological Framework

The present study explored the relationships between psychological and somatic factors in patients undergoing Coronary Artery Bypass Graft surgery (CABG). The data-analysis of previous work was extended by adding somatic factors, including feelings of disability, somatic complaints and fatigue. The focus was on their relationships with psychological factors, including anxiety, depression and neuroticism. Prior to surgery and six months postoperatively, 217 patients completed self-report questionnaires. Using the method of structural equation modeling (SEM), the structure of relationships between the somatic, psychological and background factors (i.e., gender, age and medical factors) was explored. A model was developed providing a good fit and accounting for a substantial amount of variance. The structure of relationships revealed that somatic factors lead to anxiety and depression in the preoperative period, whereas anxiety and depression lead to somatic factors in the postoperative period. The structure further strengthened the key position of neuroticism and its overall negative prognostic implications.     

Common Genetic and Environmental Influences on Major Depressive Disorder and Conduct Disorder

The evidence for common genetic and environmental influences on conduct disorder (CD) and major depressive disorder (MDD) in adolescents was examined. A sample of 570 monozygotic twin pairs, 592 dizygotic twin pairs, and 426 non-twin siblings, aged 12-18 years, was recruited from the Colorado Twin Registry. For the past year data, there was a significant correlation between the genetic influences on MDD and CD and, for the lifetime data, there was a significant correlation between the genetic influences on MDD and CD, and a significant correlation between the nonshared environmental influences on MDD and CD. Our results suggest that some genetic factors will increase an individual's vulnerability to both MDD and CD in adolescence.     

Genetic overlap between ADHD symptoms and EEG theta power

Biological markers that are grounded in neuroscience may facilitate understanding of the pathophysiology of complex psychiatric disorders. One of the most consistent and robust neural abnormalities in attention deficit hyperactivity disorder (ADHD) is increased EEG power in the theta band at rest (4–8 Hz). The present study used a twin design to estimate the extent of genetic overlap between increased theta power and risk for ADHD in order to validate theta power as a marker of genetic risk for ADHD. At rest, EEG was measured in 30 monozygotic and dizygotic adolescent twin pairs concordant or discordant for high ADHD symptom scores and 37 monozygotic and dizygotic control twin pairs with low ADHD symptom scores. Structural equation modelling was used to estimate the heritability of theta power and partition the genetic and environmental contributions to the overlap between ADHD and theta power. A significant phenotypic correlation between ADHD symptoms and elevated theta power was found. Theta power demonstrated moderate to high heritability estimates (0.77) and moderate genetic correlations with ADHD (0.35) suggesting shared genetic influences. Increased theta power is a candidate biological marker of genetic risk for ADHD, which warrants further investigation of the neurobiological mechanisms that underlie the genetic relationship.     

Etiological Distinctions between Aggressive and Non-aggressive Antisocial Behavior: Results from a Nuclear Twin Family Model

A recent meta-analysis of 103 studies Burt (Clinical Psychology Review, 29:163-178, 2009a) highlighted the presence of etiological distinctions between aggressive (AGG) and non-aggressive rule-breaking (RB) dimensions of antisocial behavior, such that AGG was more heritable than was RB, whereas RB was more influenced by the shared environment. Unfortunately, behavioral genetic research on antisocial behavior to date (and thus, the research upon which the meta-analysis was based) has relied almost exclusively on the classical twin model. This reliance is problematic, as the strict assumptions that undergird this model (e.g., shared environmental and dominant genetic influences are not present simultaneously; there is no assortative mating) can have significant consequences on heritability estimates when they are violated. The nuclear twin family model, by contrast, allows researchers to relax and statistically evaluate many of the assumptions of the classical twin design by incorporating parental self-report data along with the more standard twin data. The goal of the current study was thus to evaluate whether prior findings of etiological distinctions between AGG and RB persisted when using the nuclear twin family model. We examined a sample of 312 child twin families from the Michigan State University Twin Registry. Results strongly supported prior findings of etiological distinctions between AGG and RB, such that broad genetic influences were observed to be particularly important to AGG whereas shared environmental influences contributed only to RB. Nevertheless, the current findings also implied that additive genetic influences on antisocial behavior may be overestimated when using the classical twin design.     

Behavioral genetic analyses of prosocial behavior in adolescents

Prosocial behavior is an important aspect of normal social and psychological development. Adult and child twin studies typically estimate the heritability of prosocial behavior to be between 30 and 50%, although relatively little is known about genetic and environmental influences upon prosocial behavior in adolescence. We therefore examined reports of prosocial behavior in a large longitudinal family study of 1160 adolescent twin pairs (aged between 13 and 19 years). Prosocial behavior was assessed at two time points by self‐report and at the second time point by additional parent‐ratings using the Strengths and Difficulties Questionnaire (SDQ; Goodman, 1997 ). Adolescent females were reported to be significantly more prosocial than males (p < .001). Univariate analyses primarily showed moderate heritability and large nonshared environmental influences. There was a moderate genetic correlation between self‐ and parent‐reported prosocial behaviour, suggesting that both types of rater were tapping into genetically overlapping constructs. Longitudinal analyses revealed that continuity was largely explained by genes. Unique environmental influences were predominantly time‐specific and were the major source of individual differences.     

Genetic and Environmental Transmission of Political Orientations

This article reports results from the first twin study of adults in the United States that focuses exclusively and comprehensively on political traits. These data allow us to test whether a common set of genetic and environmental influences act upon a broad variety of values, personality traits, and political attitudes. In short, it allows us to empirically investigate whether there are a core set of predispositions that form the basis of our political orientations and, if so, whether these predispositions are shaped by the same environmental and innate forces. The key finding from our analysis is that there are core political predispositions that are rooted in common genetic and environmental influences and that these predispositions are empirically distinct from broader personality traits.     

Genetic and environmental causes of the interrelationships between self-reported fears. A study of a non-clinical sample of Norwegian identical twins and their families

The present study reports results from a study of the self-reported fears of identical twins and their spouses and offspring. Factor analysis with oblique rotation of questionnaire responses yielded four correlated fear dimensions: situational fears, illness-injury fears, social fears, and fear of small animals. Models allowing for genetic and cultural transmission, together with specially correlated environments for twins, were fitted, both for separate fears and across fears. Simple models with only genetic and uncorrelated environments were sufficient to account for each the fear dimensions considered separately. The cross-dimensional analyses revealed a genetic and an environmental factor common to the four fear dimensions, together with fear-specific genetic and environmental factors. The impact of the common genetic and common environmental factor varied across dimensions. No evidence of cultural transmission or specially correlated twin environments of the cross-dimensional environments was detected. It is concluded that both common and fear-specific genes and (individual-specific) common and fear-specific environments are necessary to account for the data. The results are discussed in terms of the prepared learning hypothesis and the expectancy bias hypothesis.