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The University of British Columbia (UBC) Twin Project is a registry of approximately 2,000 pairs of reared-together twins recruited across the major Canadian provinces. The focus of the project is an investigation of the behavioral genetics of personality and its disorders, and their relationship to other forms of mental illness. The goal is to find evidence for current diagnostic structures and classification systems, or certainly provide data for their reform. The primary measures employed are full-form self-report questionnaires of major psychological and psychiatric instruments covering personality, mood, general health, schizotypy, and more recently the anxiety disorders from symptoms resulting from exposure traumatic events, obsessive–compulsive behavior and beliefs, as well as coping strategies and health anxieties. No DNA has been collected. Data from the project have been used in several collaborative projects worldwide, and collaborative projects with other groups and interested researchers are welcomed.

AbstractPeople differ markedly in their risk for developing posttraumatic stress symptoms (PTSS) after exposure to traumatic events. Twin studies suggest that the trauma-PTSS relationship is moderated by genetic and environmental influences. The present study tested for specific types of genetic and environmental interaction effects on PTSS. A sample of 222 monozygotic and 184 dizygotic twin pairs reported on lifetime frequency of assaultive and nonassaultive trauma and associated PTSS. Biometric analyses indicated that in the case of nonassaultive trauma, PTSS were directly affected by environmental factors that also influence exposure to nonassaultive trauma. For assaultive trauma both genetic and non-shared environmental influences jointly affected PTSS, and the number of traumatic events moderated the severity of PTSS. Genetic factors were found to become less important beyond some threshold (e.g., 3 or 4 types of serious trauma) suggesting that genetic factors — which may confer either risk or resilience to PTSS — modify these symptoms within a range of human experience, beyond which environmental effects supervene.

The relationship between self-report abilities and measured intelligence was examined at both the phenotypic (zero-order) level as well as at the genetic and environmental levels. Twins and siblings (N = 516) completed a timed intelligence test and a self-report ability questionnaire, which has previously been found to produce 10 factors, including: politics, interpersonal relationships, practical tasks, intellectual pursuits, academic skills, entrepreneur/business, domestic skills, vocal abilities, and creativity. At the phenotypic level, the correlations between the ability factor scores and intelligence ranged from 0.01 to 0.42 (between self-report academic abilities and verbal intelligence). Further analyses found that some of the phenotypic relationships between self-report ability scores and measured intelligence also had significant correlations at the genetic and environmental levels, suggesting that some of the observed relationships may be due to common genetic and/or environmental factors.

The purpose of this study was to examine the phenotypic, genetic, and environmental relationships between multiple dimensions of Type A behavior and personality. Adult twins (N = 247 pairs) completed a self-report personality measure and a work style questionnaire that measured six facets of Type A behavior: impatience, anger, work involvement, time urgency, job dissatisfaction, and competitiveness. Univariate results suggest that only the job dissatisfaction facet of Type A behavior was explained by non-genetic (environmental) factors. Multivariate results suggest that all of the genetically determined facets of Type A behavior show some correspondence with at least one of the personality factors found in the study, suggesting that some of the phenotypic (observed) relationships could be due to common genetic factors.

The present research examined the extent to which relations between social values and personality are due to shared genetic or environmental factors. Using the Rokeach (1973) Value Survey and a scoring key from Schwartz and Bilsky (1990), seven value scores (enjoyment, achievement, self-direction, maturity, prosocial, security, and restrictive conformity) were derived in a sample of twins. As expected, all of the value scales were found to have a significant genetic component, with values ranging from 36% for enjoyment to 63% for prosocial, and there were numerous significant phenotypic correlations found between the value scales and personality scores. Most important, bivariate genetic analyses revealed that some of these phenotypic correlations could be attributed to common genetic or environmental factors.

AbstractThe heritability of adult attachment styles as measured by the Relationship Scales Questionnaire (RSQ) was estimated on data from a volunteer general population sample of 220 adult twin pairs (116 monozygotic pairs. 104 dizygotic pairs). Additive genetic effects accounted for 37%, 43%, and 25% of the variance in the secure, fearful, and preoccupied adult attachment styles, respectively, but none of the variance in the dismissing style. Nonshared environmental influences accounted for the majority of the variance in all styles: 63% secure, 57% fearful, 75% preoccupied, and 71% dismissing. Shared environmental effects were negligible for all styles except dismissing (29%).

AbstractPrevious behaviour genetic studies of aggression have yielded inconsistent results: reported heritabilities for different types of aggressive behaviour ranging from 0 to 0.98. In the present study, 247 adult twin pairs (183 MZ pairs; 64 same-sex DZ pairs) were administered seven self-report questionnaires which yielded 18 measures of aggression. Univariate genetic analyses showed moderate to high heritabilities for 14 of these 18 measures and for a general aggression factor and three correlated aggression factors extracted from the measures. Multivariate genetic analyses showed sizeable genetic correlations between the different dimensions of aggression. Thus, individual differences in many types of aggressive behaviour are attributable to some extent to genetic factors and there is considerable overlap between the genes that operate on different types of aggressive behaviour.

AbstractWith the recent resurgence in popularity of trait theories of leadership, it is timely to consider the genetic determination of the multiple factors comprising the leadership construct. Individual differences in personality traits have been found to be moderately to highly heritable, and so it follows that if there are reliable personality trait differences between leaders and non-leaders, then there may be a heritable component to these individual differences. Despite this connection between leadership and personality traits, however, there are no studies of the genetic basis of leadership using modern behavior genetic methodology. The present study proposes to address the lack of research in this area by examining the heritability of leadership style, as measured by self-report psychometric inventories. The Multifactor Leadership Questionnaire (MLQ), the Leadership Ability Evaluation, and the Adjective Checklist were completed by 247 adult twin pairs (183 monozygotic and 64 same-sex dizygotic). Results indicated that most of the leadership dimensions examined in this study are heritable, as are two higher level factors (resembling transactional and transformational leadership)derived from anobliquely rotated principal components factors analysis of the MLQ. Univariate analyses suggested that 48% of the variance in transactional leadership may be explained by additive heritability, and 59% of the variance in transformational leadership may be explained by non-additive (dominance) heritability. Multi-variate analyses indicatedthat most ofthe variables studiedshared substantial genetic covariance, suggesting a large overlap in the underlying genes responsible for the leadership dimensions.

Previous research has shown an association between primary headaches and some extreme features of normal personality traits, however, studies of the relationship between these headaches and the disordered or abnormal personality traits are still needed. This study sought to examine
the disordered personality trait profiles in patients with migraine, tension-type headaches compared to healthy controls. Disordered personality traits were assessed using the Dimensional Assessment of Personality Pathology (DAPP; Livesley & Jackson, in press), a self-report measure of
abnormal personality function that subsumes major models of normal personality, in 41 patients with chronic headaches (CTH), 34 frequent episodic tension-type headaches (FETH) and 48 migraine without aura, as well as 37 headache-free healthy control subjects. All patient groups scored significantly
higher than healthy controls on Submissiveness, Cognitive Distortion, Identity Problems, Intimacy Problems, Social Avoidance, and Self-Harm. In addition, the migraine group scored higher on Submissiveness than did the FETH group. Our findings thus confirmed personality dysfunctions in primary
headache sufferers.

To examine the relationship between perceptions of parenting and personality, the Parental Bonding Instrument (PBI; Parker, Tupling, & Brown, 1979) and the Dimensional Assessment of Personality Pathology – Basic Questionnaire (DAPP; Livesley & Jackson, in press) were administered
to 167 adolescent and 422 adult students, as well as to 198 patients with personality disorders. Principal component analysis of the PBI yielded 3 factors in all three samples: Care, Freedom Control, and Autonomy Denial. Chinese personality disorder patients perceived less parental Care than
did adolescent and adult students, more paternal Freedom Control than did adults, and more paternal Autonomy Denial than did adolescents. Most regression coefficients between PBI and DAPP scales were moderate, but consistent with previous literature. These findings are similar to those found
in the non-Chinese samples, suggesting that parental bonding is important in the development of personality disorders across different nations.

A cerebral P3 potential (passive P3) in response to a single tone shares similar morphology to the classical P3 elicited in the active "oddball" paradigm, but reflects passive attention. As patients with schizotypal, antisocial, and borderline personality disorders show
reduced amplitude and prolonged latency of classical P3, it is reasonable to expect that these patients might show an abnormal passive P3. We tested whether the single tone elicited event-related potentials (ERPs) in 205 patients with personality disorders and in 30 healthy volunteers. Their
Axis I symptoms of depression and anxiety were measured by Zung's Self-rating Depression Scale and Self-rating Anxiety Scale (1965, 1971). Both schizoid and paranoid groups showed significantly reduced P3 amplitude. In addition, the schizoid group showed significantly shortened N1 latency
and enhanced N2 amplitude. Most patient groups except schizoids scored higher on the Depression or Anxiety scales, or both, but the ERP findings were not correlated with the Axis I symptoms in any given group alone. The abnormal negative components implied a higher vigilance or cortical arousal
level in the schizoid patients, while the reduced P3 amplitude indicated a poorer passive attention in both schizoid and paranoid patients.