Behavioral genetics of personality

Mapping the road from childhood adversity to personality disorder: The role of unresolved states of mind

Childhood adversity has been found to be an important aetiological factor in the development of personality disorder (PD) in several studies. However, the role of disorganized attachment with unresolved mental states for traumatic experiences requires further investigation. This study explores the relationship between childhood adversities, unresolved states of mind, PD diagnosis and psychiatric distress. Two hundred forty-five adult participants, 124 from a clinical PD group and 121 non-psychiatric controls were assessed using the Structured Clinical Interview for DSM-IV, the Cassel Baseline Questionnaire, the Symptom Checklist-90-R and the Adult Attachment Interview, in order to ascertain presence of PD, childhood adversity, level of psychiatric distress and unresolved states of mind. Within the overall unresolved (U-overall) attachment category, a distinction was made between unresolved for abuse (U-abuse) and unresolved for loss (U-loss). The results indicated that childhood adversity was significantly associated with unresolved states of mind, as well as with overall PD diagnosis, paranoid PD, borderline PD, avoidant PD and psychiatric distress. Mediation analyses confirmed that U-overall and U-loss were significant mediators between childhood adversity and PD diagnoses, but surprisingly, U-abuse was not a significant mediator. The strength, limitations and clinical implications of the findings are discussed. Copyright © 2017 John Wiley & Sons, Ltd.

The heritability of Cluster B personality disorders assessed both by personal interview and questionnaire

Whereas the heritability of common personality traits has been firmly established, the results of the few published studies on personality disorders (PDs) are highly divergent, with some studies finding high heredity and others very low. A problem with assessing personality disorders by means of interview is errors connected with interviewer bias. A way to overcome the problem is to use self-report questionnaires in addition to interviews. This study used both interview and questionnaire for assessing DSM-IV Cluster B personality disorders: antisocial personality disorder (APD), borderline (BPD), narcissistic (NPD), and histrionic (HPD). We assessed close to 2,800 twins from the Norwegian Institute of Public Health Twin Panel using a self-report questionnaire and, a few years later, the Structured Interview for DSM-IV Personality (SIDP-IV). Items from the self-report questionnaire that best predicted the PDs captured by the interview were then selected. Measurement models combining questionnaire and interview information were applied and were fitted using Mx. Whereas the heritability of Cluster B PDs assessed by interview was around .30, and around .40-.50 when assessed by self-report questionnaire, the heritability of the convergent latent factor, including information from both interview and self-report questionnaire was .69 for APD, .67 for BPD, .71 for NPD, and .63 for HPD. As is usually found for personality, the effect of shared-in families (familial) environment was zero. In conclusion, when both interview and self-report questionnaire are taken into account, the heritability of Cluster B PD appears to be in the upper range of previous findings for mental disorders.

Effects of personality on use of medications, alcohol, and cigarettes during pregnancy

PURPOSE

The aim of the study was to examine the role of personality in a pregnant woman's consumption of medications, cigarettes, and alcohol.

METHODS

The study included 835 pregnant women in Norway who responded to an electronic questionnaire posted on websites for pregnant women. On the questionnaire, the women reported their use of medications, cigarettes, and alcohol during pregnancy. They also filled out a personality assessment questionnaire, the Big Five Inventory.

RESULTS

Use of medications, alcohol, and cigarettes was significantly associated with different personality traits. Women with high scores for conscientiousness were less likely to use an over-the-counter medication such as paracetamol than other women (odds ratio (OR) 0.74; 95% confidence interval (CI) 0.55-0.99). Women who scored high for neuroticism were four- to sixfold more likely to use prescription medications such as sedatives/anxiolytics (OR 4.07; 95% CI 1.48-11.20) or antidepressants (OR 5.73, 95% CI 2.33-14.09). Women with high scores for openness to experience were more likely to use herbal remedies (OR 1.59; 95% CI 1.00-2.52). Women who continued consuming alcohol during pregnancy were more likely to score high on extraversion and low on conscientiousness than women who quit alcohol use. Scoring high on neuroticism increased the likelihood of quitting smoking during pregnancy.

CONCLUSIONS

This study shows that a woman's personality traits are associated with use of medications, cigarettes, and alcohol during pregnancy. This knowledge could be of clinical importance to health care personnel providing prenatal care.

Multivariate behavior genetic analyses of aggressive behavior subtypes

This study examined the genetic and environmental architecture underlying aggressive behavior measured by the Life History of Aggression Questionnaire (LHA; Coccaro et al. 1997a). Following preliminary phenotypic factor analysis procedures, multivariate behavioral genetics models were fit to responses from 2,925 adult twins from the PennTwins cohort on five LHA items assessing lifetime frequency of temper tantrums, indirect aggression, verbal aggression, fighting, and physical assault. The best-fitting model was a 2-factor common pathway model, indicating that these five aggressive behaviors are underpinned by two distinct etiological factors with different genetic and nonshared environmental influences. Although there was evidence of significant sex differences, the structure of the two factors appeared to be quite similar in males and females, where General Aggression and Physical Aggression factors emerged. Heritability of these factors ranged from .37 to .57, and nonshared environmental effects ranged from .43 to .63. The results of this study highlight the heterogeneous nature of the aggression construct and the need to consider differences in genetic and environmental influences on individual aggressive behaviors in a multivariate context.

Dimensional representations of DSM-IV cluster B personality disorders in a population-based sample of Norwegian twins: a multivariate study

BACKGROUND

The personality disorders (PDs) in the 'dramatic' cluster B [antisocial (ASPD), histrionic (HPD), narcissistic (NPD) and borderline (BPD)] demonstrate co-morbidity. However, the degree to which genetic and/or environmental factors influence their co-occurrence is not known and, with the exception of ASPD, the relative impact of genetic and environmental risk factors on liability to the cluster B PDs has not been conclusively established.

METHOD

PD traits were assessed in 1386 Norwegian twin pairs between the age of 19 and 35 years using the Structured Interview for DSM-IV Personality Disorders (SIDP-IV). Using the statistical package Mx, multivariate twin models were fitted to dimensional representations of the PDs.

RESULTS

The best-fitting model, which did not include sex or shared family environment effects, included common genetic and environmental factors influencing all four dramatic PD traits, and factors influencing only ASPD and BPD. Heritability was estimated at 38% for ASPD traits, 31% for HPD traits, 24% for NPD traits and 35% for BPD traits. BPD traits had the lowest and ASPD traits the highest disorder-specific genetic variance.

CONCLUSION

The frequently observed co-morbidity between cluster B PDs results from both common genetic and environmental influences. Etiologically, cluster B has a 'substructure' in which ASPD and BPD are more closely related to each other than to the other cluster B disorders.

The molecular genetic architecture of human personality: beyond self-report questionnaires

Molecular genetic studies of personality began with two high impact papers in 1996 that showed provisional associations between the dopamine DRD4 exon III repeat region and Novelty Seeking/Extraversion. These first two reports were shortly followed by an investigation linking Neuroticism/Harm Avoidance with the serotonin transporter (SLC6A4) promoter region polymorphism (5-HTTLPR). In the ensuing decade, thousands of subjects have been studied for association between these genes and personality, assessed by using self-report questionnaires, with erratic success in replication of the first findings for Novelty Seeking (DRD4) and Harm Avoidance (5-HTTLPR). Small effect sizes characteristic of non-Mendelian traits, polygenic patterns of inheritance and true heterogeneity between studies confound attempts to reach a consensus regarding the role of common polymorphisms in contributing to personality domains. Nevertheless, the current state of personality genetics is far from being bleak. Several new paradigms especially functional neuroimaging or 'imaging genomics' have strengthened the connection between 5-HTTLPR and anxiety-related personality traits. The demonstrations that early environmental information can considerably strengthen and even uncover associations between genes and behavior (Caspi's seminal studies and more recently the demonstration that early environment impacts on DRD4 and Novelty Seeking) are notable and herald a new era of personality genetics. Finally, consideration of the broader phenotypic expression of common polymorphisms (e.g. the 'social brain', altruism, etc.) and the use of new experimental paradigms including neurophysiological, neuropsychological and computer games that go beyond the narrow self-report questionnaire design will enable a deeper understanding of how common genetic polymorphisms modulate human behavior. Human personality, defined by Webster as the quality or state of being a person or the complex of characteristics that distinguishes an individual, surely requires a more encompassing view towards understanding its complex molecular genetic architecture.