Genetic and environmental influences on the junior temperament and character inventory in a preadolescent twin sample

The influence of genes on "positive valence systems" constructs: A systematic review

In 2009, the U.S. National Institute of Mental Health (NIMH) proposed an approach toward the deconstruction of psychiatric nosology under the research domain criteria (RDoC) framework. The overarching goal of RDoC is to identify robust, objective measures of behavior, emotion, cognition, and other domains that are more closely related to neurobiology than are diagnoses. A preliminary framework has been constructed, which has connected molecules, genes, brain circuits, behaviors, and other elements to dimensional psychiatric constructs. Although the RDoC framework has salience in emerging studies, foundational literature that pre-dated this framework requires synthesis and translation to the evolving objectives and nomenclature of RDoC. Toward this end, we review the candidate-gene association, linkage, and genome-wide studies that have implicated a variety of loci and genetic polymorphisms in selected Positive Valence Systems (PVS) constructs. Our goal is to review supporting evidence to currently listed genes implicated in this domain and novel candidates. We systematically searched and reviewed literature based on keywords listed under the June, 2011, edition of the PVS matrix on the RDoC website (http://www.nimh.nih.gov/research-priorities/rdoc/positive-valence-systems-workshop-proceedings.shtml), which were supplemented with de novo keywords pertinent to the scope of our review. Several candidate genes linked to the PVS framework were identified from candidate-gene association studies. We also identified novel candidates with loose association to PVS traits from genome-wide studies. There is strong evidence suggesting that PVS constructs, as currently conceptualized under the RDoC initiative, index genetically influenced traits; however, future research, including genetic epidemiological, and psychometric analyses, must be performed.

Some personality traits converge gradually by long-term partnership through the lifecourse--genetic and environmental structure of Cloninger's temperament and character dimensions

Temperament and Character Inventory (TCI) is a comprehensive personality inventory that is widely used in behavioral genetics. The original theory suggested that temperament traits were under genetic influences, whereas character traits were gradually built by an interaction between temperaments and environment until early adulthood. This study attempted to evaluate TCI by examining the genetic and environmental contributions to personality with particular attention to spousal effects. From 687 families, a total of 3459 Korean adult individuals completed the survey. Among them, there were 542 Monozygotic (MZ) twin pairs and 122 Dizygotic twin pairs. Intraclass correlation coefficients (ICCs) and heritability were calculated to examine the genetic and shared environmental contributions to personality. Moderate genetic contributions (0.17-0.43) were found for all TCI traits along with the evidence of shared environment (0.11-0.31) for harm avoidance (HA) and all characters. The ICCs of TCI in MZ pairs ranged 0.36-0.46. Spouses' had little resemblance for temperament, whereas for character dimensions, spouses (0.27-0.38) were more similar than first degree relatives (0.10-0.29). Resemblance between spouses increased with duration of marriage for most characters and HA. When the growing similarities between spouses were compared with their MZ cotwins' for subgroup of 81 trios, self-directedness (SD) of character showed even more similarities toward their spouses than cotwins as partnership duration increased (r = 0.32). Our findings with regard to change in SD into late adulthood support the psychobiological theory of temperament and character, which suggests that both personality domains have distinct developmental trajectories despite equally large genetic influences.

Pro-bullying attitudes among incarcerated juvenile delinquents: antisocial behavior, psychopathic tendencies and violent crime

The objective was to evaluate a new scale aimed at assessing antisocial attitudes, the Pro-bullying Attitude Scale (PAS), on a group of 259 voluntarily-recruited male juvenile delinquents from a juvenile correctional institution in Arkhangelsk, North-western Russia. Exploratory factor analysis gave a two-factor solution: Factor 1 denoted Callous/Dominance and Factor 2 denoted Manipulativeness/Impulsiveness. Subjects with complete data on PAS and Childhood Psychopathy Scale (CPS) (n=171) were divided into extreme groups (first and fourth quartiles) according to their total scores on PAS and the two factor scores, respectively. The extreme groups of total PAS and PAS Factor 1 differed in CPS ratings and in violent behavior as assessed by the Antisocial Behavior Checklist (ABC). They also differed in the personality dimension Harm Avoidance as measured by use of the Temperament and Character Inventory (TCI), and in delinquent and aggressive behavior as assessed by the Youth Self Report (YSR). The extreme groups of PAS Factor 2, in turn, differed in aggressive behavior as assessed by the YSR, and in the TCI scale Self-Directedness. When PAS was used as a continuous variable, total PAS and PAS Factor 1 (Callous/Dominance) were significantly positively related to registered violent crime. The possible usefulness of PAS in identifying high-risk individuals for bullying tendencies among incarcerated delinquents is discussed.

Examining the etiological associations among higher-order temperament dimensions

A multivariate independent pathway model was used to examine the shared and unique genetic and environmental influences of Positive Affect (PA), Negative Affect (NA), and effortful control (EC) in a sample of 686 twin pairs (M age = 10.07, SD = 1.74). There were common genetic influences and nonshared environmental influences shared across all three temperament dimensions and shared environmental influences in common to NA and EC. There were also significant independent genetic influences unique to PA and NA and significant independent shared environmental influences unique to PA. This study demonstrates that there are genetic and environmental influences that affect the covariance among temperament dimensions as well as unique genetic and environmental influences that influence the dimensions independently.

Metabolic syndrome prevalence in different affective temperament profiles in bipolar-I disorder

OBJECTIVE

Temperament originates in the brain structure, and individual differences are attributable to neural and physiological function differences. It has been suggested that temperament is associated with metabolic syndrome (MetS) markers, which may be partly mediated by lifestyle and socioeconomic status. Therefore, we aim to compare MetS prevalence between different affective temperamental profiles for each season in bipolar patients.

METHODS

Twenty-six bipolar type-I patients of a specialized outpatient mood disorder unit were evaluated for MetS according to new definition proposed by the International Diabetes Federation in the four seasons of a year. Temperament was assessed using the Temperament Evaluation of Memphis, Pisa, Paris and San Diego - autoquestionnaire version (TEMPS-A).

RESULTS

The proportions of MetS were 19.2, 23.1, 34.6, and 38.5% in the summer, fall, spring, and winter, respectively. Only depressive temperament scores were higher (p = 0.002) during the winter in patients with MetS.

CONCLUSION

These data suggest that depressive temperament profiles may predispose an individual to the development of MetS in the winter.

Etiological contributions to the covariation between children's perceptions of inter-parental conflict and child behavioral problems

Prior work has suggested that inter-parental conflict likely plays an etiological role in child behavior problems. However, family-level measurement of inter-parental conflict in most traditional child twin studies has made it difficult to tease apart the specific causal mechanisms underlying this association. The Children's Perception of Inter-parental Conflict scale (CPIC) provides a child-specific measurement tool for examining these questions, as its subscales tap multiple dimensions of conflict assessed from the child's (rather than the parent's) perspective. The current study examined (1) the degree of genetic and environmental influence on each of the CPIC subscales, and (2) etiological contributions to the covariation between the CPIC scales and parental reports of child behavioral problems. The CPIC was completed by 1,200 child twins (aged 6-11 years) from the Michigan State University Twin Registry (MSUTR). Parents completed the Child Behavior Checklist (CBCL) to assess child internalizing and externalizing behavior problems. Multivariate models were examined to evaluate the relative contributions of genetic and environmental factors to both the CPIC scales and to their overlap with child behavioral outcomes. Modeling results indicated no significant moderation of sex or age. Significant environmental overlap emerged between the CPIC conflict properties scale and child internalizing and externalizing problems. By contrast, significant genetic correlations emerged between the CPIC self-blame scale and externalizing problems as well as between the CPIC threat scale and internalizing problems. Overall, findings suggest that the subscales of the CPIC are somewhat etiologically diverse and may provide a useful tool for future investigations of possible gene-environment interplay.

Temperament, character and serotonin activity in the human brain: a positron emission tomography study based on a general population cohort

BACKGROUND

The psychobiological model of personality by Cloninger and colleagues originally hypothesized that interindividual variability in the temperament dimension 'harm avoidance' (HA) is explained by differences in the activity of the brain serotonin system. We assessed brain serotonin transporter (5-HTT) density in vivo with positron emission tomography (PET) in healthy individuals with high or low HA scores using an 'oversampling' study design. Method Subjects consistently in either upper or lower quartiles for the HA trait were selected from a population-based cohort in Finland (n = 2075) with pre-existing Temperament and Character Inventory (TCI) scores. A total of 22 subjects free of psychiatric and somatic disorders were included in the matched high- and low-HA groups. The main outcome measure was regional 5-HTT binding potential (BPND) in high- and low-HA groups estimated with PET and [11C]N,N-dimethyl-2-(2-amino-4-methylphenylthio)benzylamine ([11C]MADAM). In secondary analyses, 5-HTT BPND was correlated with other TCI dimensions.

RESULTS

5-HTT BPND did not differ between high- and low-HA groups in the midbrain or any other brain region. This result remained the same even after adjusting for other relevant TCI dimensions. Higher 5-HTT BPND in the raphe nucleus predicted higher scores in 'self-directedness'.

CONCLUSIONS

This study does not support an association between the temperament dimension HA and serotonin transporter density in healthy subjects. However, we found a link between high serotonin transporter density and high 'self-directedness' (ability to adapt and control one's behaviour to fit situations in accord with chosen goals and values). We suggest that biological factors are more important in explaining variability in character than previously thought.

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.

Contributions of dopamine-related genes and environmental factors to highly sensitive personality: a multi-step neuronal system-level approach

Traditional behavioral genetic studies (e.g., twin, adoption studies) have shown that human personality has moderate to high heritability, but recent molecular behavioral genetic studies have failed to identify quantitative trait loci (QTL) with consistent effects. The current study adopted a multi-step approach (ANOVA followed by multiple regression and permutation) to assess the cumulative effects of multiple QTLs. Using a system-level (dopamine system) genetic approach, we investigated a personality trait deeply rooted in the nervous system (the Highly Sensitive Personality, HSP). 480 healthy Chinese college students were given the HSP scale and genotyped for 98 representative polymorphisms in all major dopamine neurotransmitter genes. In addition, two environment factors (stressful life events and parental warmth) that have been implicated for their contributions to personality development were included to investigate their relative contributions as compared to genetic factors. In Step 1, using ANOVA, we identified 10 polymorphisms that made statistically significant contributions to HSP. In Step 2, these polymorphism's main effects and interactions were assessed using multiple regression. This model accounted for 15% of the variance of HSP (p<0.001). Recent stressful life events accounted for an additional 2% of the variance. Finally, permutation analyses ascertained the probability of obtaining these findings by chance to be very low, p ranging from 0.001 to 0.006. Dividing these loci by the subsystems of dopamine synthesis, degradation/transport, receptor and modulation, we found that the modulation and receptor subsystems made the most significant contribution to HSP. The results of this study demonstrate the utility of a multi-step neuronal system-level approach in assessing genetic contributions to individual differences in human behavior. It can potentially bridge the gap between the high heritability estimates based on traditional behavioral genetics and the lack of reproducible genetic effects observed currently from molecular genetic studies.

Contributions of parent-adolescent negative emotionality, adolescent conflict, and adoption status to adolescent externalizing behaviors

Although most adopted children are well adjusted, research has consistently found that adopted adolescents are at an increased risk for externalizing behaviors. The present investigation tested a model whereby parent-adolescent negative emotionality traits, adolescent conflict, and adoption status contribute to adolescent externalizing behaviors. The study included 616 families with at least one parent and two adolescent siblings with a maximum 5-year age difference. The analyses used data from the mothers (M age = 45.56, SD = 4.23), fathers (M age = 48.23, SD = 4.42), and the elder sibling (M age = 16.14, SD = 1.5). Findings support two conflict-mediated family processes that contributed to externalizing behaviors: one initiated by parent-adolescent traits and one by adoption status. Findings also underscore the salience of conflict in families and the significance of aggressive traits and negative emotionality. Contrary to previous research, we found that adoption status did not directly add to our explanation of adolescent externalizing behaviors beyond our proposed process. Instead, adoption status was indirectly associated with externalizing problems through a conflict-mediated relationship.

Prevalence of pattern of risky behaviors for reproductive and sexual health among middle- and high-school students

This research aimed to establish the prevalence and factors associated with the pattern of risky behavior for reproductive and sexual health (PRBRSH) among secondary education students in Santa Marta, Colombia. A cross-sectional study was done. The PRBRSH was defined as having had two or more out of four possible risky sexual practices across the lifetime. Logistic regression was calculated to control for confounding variables. In total, 804 students reported lifetime sexual intercourse. PRBRSH was reported by 36.1% of the sample. Illegal substance use (OR=11.4), alcohol drinking (OR=2.5), being a middle-school student (OR=1.7) and middle or high socioeconomic status (1.4) were associated with PRBRSH. Around one out of three adolescent students is at high risk for HIV infection or unwanted pregnancy. Safe sex practices need to be promoted in this population.