Nature and nurture in novelty seeking

Uncovering the complex genetics of human character

Human personality is 30-60% heritable according to twin and adoption studies. Hundreds of genetic variants are expected to influence its complex development, but few have been identified. We used a machine learning method for genome-wide association studies (GWAS) to uncover complex genotypic-phenotypic networks and environmental interactions. The Temperament and Character Inventory (TCI) measured the self-regulatory components of personality critical for health (i.e., the character traits of self-directedness, cooperativeness, and self-transcendence). In a discovery sample of 2149 healthy Finns, we identified sets of single-nucleotide polymorphisms (SNPs) that cluster within particular individuals (i.e., SNP sets) regardless of phenotype. Second, we identified five clusters of people with distinct profiles of character traits regardless of genotype. Third, we found 42 SNP sets that identified 727 gene loci and were significantly associated with one or more of the character profiles. Each character profile was related to different SNP sets with distinct molecular processes and neuronal functions. Environmental influences measured in childhood and adulthood had small but significant effects. We confirmed the replicability of 95% of the 42 SNP sets in healthy Korean and German samples, as well as their associations with character. The identified SNPs explained nearly all the heritability expected for character in each sample (50 to 58%). We conclude that self-regulatory personality traits are strongly influenced by organized interactions among more than 700 genes despite variable cultures and environments. These gene sets modulate specific molecular processes in brain for intentional goal-setting, self-reflection, empathy, and episodic learning and memory.

Candidate genes for novelty-seeking: a meta-analysis of association studies of DRD4 exon III and COMT Val158Met

OBJECTIVE

Two widely studied genetic polymorphisms in the dopaminergic system [DRD4 exon III variable number of tandem repeat (VNTR) and COMT Val158Met] have been reported to be associated with novelty-seeking, but the results have been highly inconsistent. Therefore, a meta-analysis of the associations between these two polymorphisms and novelty-seeking was conducted.

PARTICIPANTS AND METHODS

For DRD4, 24 studies comprising 27 samples and including 4933 participants were selected. Genotype grouping, sex, mean age, ethnicity, and sample characteristics were examined as moderators. For COMT, nine studies comprising 13 samples and including 2633 participants were selected. Sex, mean age, ethnicity, and sample characteristics were included as moderators. We also tested for possible publication bias.

RESULTS

The significant association between the DRD4 polymorphism and novelty-seeking was supported, but no association was found between the COMT polymorphism and novelty-seeking. In addition, our findings revealed that sex and age both directly moderate the relationship between DRD4 and novelty-seeking. Meanwhile, ethnicity can interact with age, sex, and genotype grouping, and age and sex can interact with each other, to moderate the association between the DRD4 exon III VNTR polymorphism and novelty-seeking.

CONCLUSION

Our results provide evidence of association between the DRD4 exon III VNTR polymorphism and novelty-seeking, which is inconsistent with the results of previous meta-analysis. Furthermore, several direct and indirect moderators are also identified to explain contradictory results in the existing literature. However, our results regarding COMT are consistent with those of previous meta-analysis.

Differential effects of clomipramine on depression-like behaviors induced by the chronic social defeat paradigm in tree shrews

BACKGROUND

Anhedonia is a hallmark symptom in major depression that reflects deficits in hedonic capacity and it is also linked to motivation for reward. However, studies of the features of motivation in depressed tree shrews are rather sparse.

AIMS

The study aimed to investigate the core feature of depression including lack of interest, motivation reduction, and social avoidance in tree shrews. Furthermore, the effects of the treatment using clomipramine on these depression-like behaviors were assessed.

METHODS

The paradigm of chronic social defeat in tree shrews was used to evaluate the core feature of depression through examining their sucrose preference, break-point for reward, and social interaction.

RESULTS

The results showed that social defeat lowered the curves of the sucrose preference and the break-point, as well as decreased social interaction. The results suggested that the subordinate animals exhibited interest loss, motivational reduction, and social avoidance. After oral treatment with clomipramine (50 mg/kg/day) for four weeks, most of the depression-like behaviors were reversed, whereas the motivational reduction was not clearly affected. Notably, the motivational reduction appeared obviously during the first week after the social defeat, and the conventional tricyclic antidepressant clomipramine did not reverse the reduced motivation.

CONCLUSIONS

These findings imply that motivational variation might be applied as a more sensitive behavioral index in subordinate animals and could furthermore be used to evaluate potential agents as antidepressants.

A systems approach to physiologic evolution: From micelles to consciousness

A systems approach to evolutionary biology offers the promise of an improved understanding of the fundamental principles of life through the effective integration of many biologic disciplines. It is presented that any critical integrative approach to evolutionary development involves a paradigmatic shift in perspective, more than just the engagement of a large number of disciplines. Critical to this differing viewpoint is the recognition that all biological processes originate from the unicellular state and remain permanently anchored to that phase throughout evolutionary development despite their macroscopic appearances. Multicellular eukaryotic development can, therefore, be viewed as a series of connected responses to epiphenomena that proceeds from that base in continuous iterative maintenance of collective cellular homeostatic equipoise juxtaposed against an ever-changing and challenging environment. By following this trajectory of multicellular eukaryotic evolution from within unicellular First Principles of Physiology forward, the mechanistic nature of complex physiology can be identified through a step-wise analysis of a continuous arc of vertebrate evolution based upon serial exaptations.

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.

Parents' personality clusters and eating disordered daughters' personality and psychopathology

The present study explores how parents' personality clusters relate to their eating disordered daughters' personality and psychopathology. Mothers and fathers were tested with the Temperament Character Inventory. Their daughters were assessed with the following: Temperament and Character Inventory, Eating Disorder Inventory-2, Symptom Checklist-90, Parental Bonding Instrument, Attachment Style Questionnaire, and Family Assessment Device. Daughters' personality traits and psychopathology scores were compared between clusters. Daughters' features were related to those of their parents. Explosive/adventurous mothers were found to relate to their daughters' borderline personality profile and more severe interoceptive awareness. Mothers' immaturity was correlated to their daughters' higher character immaturity, inadequacy, and depressive feelings. Fathers who were explosive/methodic correlated with their daughters' character immaturity, severe eating, and general psychopathology. Fathers' character immaturity only marginally related to their daughters' specific features. Both parents' temperament clusters and mothers' character clusters related to patients' personality and eating psychopathology. The cluster approach to personality-related dynamics of families with an individual affected by an eating disorder expands the knowledge on the relationship between parents' characteristics and daughters' illness, suggesting complex and unique relationships correlating parents' personality traits to their daughters' disorder.

Application of the seven-factor-model of personality to an italian preschool sample

OBJECTIVE

Advances in dimensional assessment of children in healthy and clinical populations has renewed interest in the study of temperament. Cloninger's Temperament and Character Inventory (TCI) has shown high reliability and internal consistency. Adult and adolescent versions have been translated into a number of languages and validated in cross-cultural studies worldwide. To date only one preschool-TCI-based study has been conducted in early infancy with teachers as observers. The present study is aimed to test an Italian Preschool version of the Temperament and Character Inventory (PsTCI). This is the first replication and the first validation study of TCI on preschoolers with parents as observers.

METHODS

395 preschool children, recruited from pediatric communities and day-care centres throughout Italy, participated in the study. Parents of each child enrolled in the study and completed a PsTCI about the child. Standard psychometric tests of reliability and validation were performed.

RESULTS

Exploratory factor analyses demonstrated the presence of distinct domains for temperament and character. TCI dimensions had good internal consistency with Cronbach's alpha ranging values (|0.60|-|0.81|). Gender differences were found for Harm Avoidance (β=-0.186; p≤0.001) and Self-Directedness (β=-0.216; p≤0.01), and accounted for 5-35arm-38-702- of the observed variance.

CONCLUSION

The present work suggests the psychological complexity of Cloninger's model and confirms its application in pre-school children from diverse environmental and cultural backgrounds. The results confirm that Cloninger's instrument for temperament and character evaluations can also be used with different observers and highlight the importance of considering cultural and demographic differences in the assessment of temperament and character in preschoolers.

Gene × environment interaction studies have not properly controlled for potential confounders: the problem and the (simple) solution

Candidate gene × environment (G × E) interaction research tests the hypothesis that the effects of some environmental variable (e.g., childhood maltreatment) on some outcome measure (e.g., depression) depend on a particular genetic polymorphism. Because this research is inherently nonexperimental, investigators have been rightly concerned that detected interactions could be driven by confounders (e.g., ethnicity, gender, age, socioeconomic status) rather than by the specified genetic or environmental variables per se. In an attempt to eliminate such alternative explanations for detected G × E interactions, investigators routinely enter the potential confounders as covariates in general linear models. However, this practice does not control for the effects these variables might have on the G × E interaction. Rather, to properly control for confounders, researchers need to enter the covariate × environment and the covariate × gene interaction terms in the same model that tests the G × E term. In this manuscript, I demonstrate this point analytically and show that the practice of improperly controlling for covariates is the norm in the G × E interaction literature to date. Thus, many alternative explanations for G × E findings that investigators had thought were eliminated have not been.

Gene-environment studies and borderline personality disorder: a review

We review recent gene-environment studies relevant to borderline personality disorder, including those focusing on impulsivity, emotion sensitivity, suicidal behavior, aggression and anger, and the borderline personality phenotype itself. Almost all the studies reviewed suffered from a number of methodological and statistical problems, limiting the conclusions that currently can be drawn. The best evidence to date supports a gene-environment correlation (rGE) model for borderline personality traits and a range of adverse life events, indicating that those at risk for BPD are also at increased risk for exposure to environments that may trigger BPD. We provide suggestions regarding future research on GxE interaction and rGE effects in borderline personality.

Polymorphic variation in the dopamine D4 receptor predicts delay discounting as a function of childhood socioeconomic status: evidence for differential susceptibility

Inconsistent or null findings among studies associating behaviors on the externalizing spectrum--addictions, impulsivity, risk-taking, novelty-seeking traits--with presence of the 7-repeat allele of a common length polymorphism in the gene encoding the dopamine D4 receptor (DRD4) may stem from individuals' variable exposures to prominent environmental moderators (gene × environment interaction). Here, we report that relative preference for immediate, smaller rewards over larger rewards delayed in time (delay discounting), a behavioral endophenotype of impulsive decision-making, varied by interaction of DRD4 genotype with childhood socioeconomic status (SES) among 546 mid-life community volunteers. Independent of age, sex, adulthood SES and IQ, participants who were both raised in families of distinctly low SES (low parental education and occupational grade) and carried the DRD4 7-repeat allele discounted future rewards more steeply than like-reared counterparts of alternate DRD4 genotype. In the absence of childhood socioeconomic disadvantage, however, participants carrying the 7-repeat allele discounted future rewards less steeply. This bidirectional association of DRD4 genotype with temporal discounting, conditioned by participants' early life circumstances, accords with a recently proposed developmental model of gene × environment interaction ('differential susceptibility') that posits genetically modulated sensitivity to both adverse and salubrious environmental influences.

Religion priming differentially increases prosocial behavior among variants of the dopamine D4 receptor (DRD4) gene

Building on gene-environment interaction (G × E) research, this study examines how the dopamine D4 receptor (DRD4) gene interacts with a situational prime of religion to influence prosocial behavior. Some DRD4 variants tend to be more susceptible to environmental influences, whereas other variants are less susceptible. Thus, certain life environments may be associated with acts of prosociality for some DRD4 variants but not others. Given that religion can act as an environmental influence that increases prosocial behavior, environmental input in the form of religion priming may have G × E effects. Results showed that participants with DRD4 susceptibility variants were more prosocial when implicitly primed with religion than not primed with religion, whereas participants without DRD4 susceptibility variants were not impacted by priming. This research has implications for understanding why different people may behave prosocially for different reasons and also integrates G × E research with experimental psychology.

Dopamine D4 receptor gene associated with fairness preference in ultimatum game

In experimental economics, the preference for reciprocal fairness has been observed in the controlled and incentivized laboratory setting of the ultimatum game, in which two individuals decide on how to divide a sum of money, with one proposing the share while the second deciding whether to accept. Should the proposal be accepted, the amount is divided accordingly. Otherwise, both would receive no money. A recent twin study has shown that fairness preference inferred from responder behavior is heritable, yet its neurogenetic basis remains unknown. The D4 receptor (DRD4) exon3 is a well-characterized functional polymorphism, which is known to be associated with attention deficit hyperactivity disorder and personality traits including novelty seeking and self-report altruism. Applying a neurogenetic approach, we find that DRD4 is significantly associated with fairness preference. Additionally, the interaction among this gene, season of birth, and gender is highly significant. This is the first result to link preference for reciprocal fairness to a specific gene and suggests that gene × environment interactions contribute to economic decision making.

The Multiple, Distinct Ways that Personality Contributes to Alcohol Use Disorders

There is little question of whether personality is associated with problematic alcohol involvement (such as alcohol use disorders; AUDs); it clearly is. However, the question remains: how or why is personality related to risky drinking and AUDs? To address this question, theoretical models have been posited regarding the causal effects of personality on alcohol use and related problems. In this article, several of these models are summarized and reviewed. Future research directions are discussed, including possible frameworks that serve to integrate various models of the personality-AUD relation.

Gender-specific expression of the DRD4 gene on adolescent delinquency, anger and thrill seeking

The present study investigated gender differences in the associations between the DRD4 variable number tandem repeat (VNTR) polymorphism and adolescent delinquency, short temper and thrill seeking. We also explored whether the gender-specific expression of the DRD4 can be explained by gender differences in the exposure to psychosocial risks, such as poor parent-child relationship. Participants were 263 14- to 17-year olds (50% males) living in Russia. DNA was extracted from saliva samples and the VNTR DRD4 polymorphisms were genotyped using polymerase chain reaction. Participants reported on the extent of their delinquent behaviour, short temper, thrill seeking and exposure to psychosocial risk (i.e. poor parental monitoring of adolescent behaviour, exposure to violence and peer delinquency). Compared to individuals with the 4/4 genotype, males, but not females, with the 7-repeat allele (7R) had significantly higher delinquency, short temper and thrill seeking. This interaction effect, however, was completely explained by males' higher exposure to psychosocial risk factors. When parental monitoring of youths' activities and youth exposure to violence were included in the model, the 7R × gender interaction was no longer significant. Thus, social context plays an important role in explaining gender-specific phenotypic expression of the DRD4 gene.

Dopamine and serotonin systems modify environmental effects on human behavior: a review

The relative influences of genetic and environmental factors in the development of human behavior have been a long-term topic for an intense debate. Recent behavioral genetic studies suggest focusing on the joint effect of genes and environment, and especially on the life-course developmental interplay between nature and nurture. Vulnerability to environmental adversities and sensitivity to its benefits may be conditional on genetic background, and regarding psychological outcomes, these kinds of gene x environment interactions may be of higher importance than direct gene-trait associations. In our recent series of studies, we have shown that different variants of serotonergic and dopaminergic genes may moderate the influence of environmental conditions on a range of psychological outcomes, i.e. temperament, depression, hostility, and educational attainment. These studies suggest that depending on their genotype, people may be differentially sensitive to the environmental conditions they encounter. In the light of these results it seems highly plausible that the effects of genes may become evident only when studied in the context of environmental factors.

Applying a Psychobiological Model of Personality to the Study of Leadership

Cloninger’s psychobiological model of temperament and character is a general model of personality that has been widely used in clinical psychology, but has seldom been applied in other domains. In this research we apply Cloninger’s model to the study of leadership. Our study comprised 81 participants who took part in a diverse range of small group tasks. Participants rotated through tasks and groups and rated each other on “emergent leadership.” As hypothesized, leader emergence tended to be consistent regardless of the specific tasks and groups. It was found that personality factors from Cloninger, Svrakic, and Przybeck’s (1993) model could explain trait-based variance in emergent leadership. Results also highlight the role of “cooperativeness” in the prediction of leadership emergence. Implications are discussed in terms of our theoretical understanding of trait-based leadership, and more generally in terms of the utility of Cloninger’s model in leadership research.

Genetic and gene-environment interaction effects on preschoolers' social behaviors

This study examined effects from a specific dopamine receptor gene (DRD4), environmental influences from parents and peers, and the interaction between them, on aggressive and prosocial behaviors of preschoolers. Children were classified as DRD4-L (n = 27) if they had at least one DRD4 allele with six to eight repeats and as DRD4-S (n = 35) if not. Parent-child interactions were coded when children were 3-4 years old. Peer interaction data and parent questionnaires were collected at age 5. DRD4-L children shared less with each other and parents were less sensitive during parent-twin triadic interactions. Also, genotype interacted with peer aggression to affect children's aggression during a peer play interaction at age 5, and genotype interacted with prior parental sensitivity to affect later externalizing problems. Thus, children having a certain genetic disposition may be more sensitive to certain environmental stimuli and therefore more likely to exhibit aggressive behaviors under more stressful circumstances.

Impact of the dopamine receptor gene family on temperament traits in a population-based birth cohort

Although the genetic determinants of personality have been intensively investigated especially since Cloninger proposed his psychobiological model of temperament and character, findings to date remain inconclusive and very few studies have addressed the topic in large population cohorts. In the current study we investigated one gene family in its entirety by addressing the role of all known dopamine receptor genes, DRD1-DRD5, on Cloninger's temperament traits in a Finnish population-based birth cohort. The study sample (n = 1,434) was ascertained from the Northern Finland Birth Cohort 1966 with over 5,000 study individuals tested at the age of 31 years. We utilized the genetic homogeneity and genealogical structure of this population to uncover putative effects of these genes on temperament traits at the population level. Our strategy utilizing a large birth cohort and its well established genealogical structure represents an optimal design for studying normally distributed traits. We also wished to provide a comprehensive view to one biologically relevant gene family instead of testing single candidate genes. We report evidence of association of several SNPs at the 5' end of dopamine receptor D2 (DRD2) with Novelty seeking (low) and Harm avoidance (high), and at the 3' end of DRD2 with Persistence. The strongest evidence of association emerged from females. Our study supports the involvement of the dopamine pathway in temperament traits, in particular underlining the role of DRD2 in Novelty seeking, Harm avoidance and Persistence.

Pessimistic, anxious, and depressive personality traits predict all-cause mortality: the Mayo Clinic cohort study of personality and aging

OBJECTIVE

To study the association between several personality traits and all-cause mortality.

METHODS

We established a historical cohort of 7216 subjects who completed the Minnesota Multiphasic Personality Inventory (MMPI) for research at the Mayo Clinic from 1962 to 1965, and who resided within a 120-mile radius centered in Rochester, MN. A total of 7080 subjects (98.1%) were followed over four decades either actively (via a direct or proxy telephone interview) or passively (via review of medical records or by obtaining their death certificates). We examined the association of pessimistic, anxious, and depressive personality traits (as measured using MMPI scales) with all-cause mortality.

RESULTS

A total of 4634 subjects (65.5%) died during follow-up. Pessimistic, anxious, and depressive personality traits were associated with increased all-cause mortality in both men and women. In addition, we observed a linear trend of increasing risk from the first to the fourth quartile for all three scales. Results were similar in additional analyses considering the personality scores as continuous variables, in analyses combining the three personality traits into a composite neuroticism score, and in several sets of sensitivity analyses. These associations remained significant even when personality was measured early in life (ages 20-39 years).

CONCLUSIONS

Our findings suggest that personality traits related to neuroticism are associated with an increased risk of all-cause mortality even when they are measured early in life.

DRD2 C32806T modifies the effect of child-rearing environment on adulthood novelty seeking

Preliminary evidence suggests that there may be longitudinal interactions between environmental and genetic factors in predicting Novelty seeking. We have previously found in small and selected subsample from the Cardiovascular Risk in Young Finns study, that an association between the polymorphism of dopamine receptor D4 was moderated by the childhood environment, as indexed by hostile maternal child-rearing. We wanted to replicate this finding in a population based sample of 1,114 men and women using another candidate gene of dopaminergic system, that is, the dopamine receptor D2 (DRD2). The child-rearing environment of the participants was assessed by their mothers when the participants were children or adolescents, and adulthood Novelty seeking was self-rated by the participants 17 and 21 years later at the ages of 24-39. Genotyping of DRD2 C32806T (rs 1800497) was performed using TaqMan 5'nuclease assay. DRD2 was not directly associated with Novelty seeking, but there was a significant DRD2 x strict maternal disciplinary style interaction in predicting Novelty seeking (F = 7.08, P = 0.008). The interaction showed that when the child-rearing environment was punitive, participants carrying any A1 allele of the DRD2 gene had higher scores on Novelty seeking than carriers of the A2/A2 genotype. The genotype had no effect on Novelty seeking when the childhood environment was more favorable. The findings suggest that the DRD2 may have an environmentally moderated impact on Novelty seeking and that the origins of such an association may lie already in childhood.

Association of the dopamine D4 receptor (DRD4) gene and approach-related personality traits: meta-analysis and new data

BACKGROUND

Two variants in the dopamine D4 receptor (DRD4) gene have been reported to be associated with human approach-related traits such as novelty seeking and extraversion. However, the strength of evidence for this association remains uncertain.

METHODS

We conducted a meta-analysis of published studies of the association between the DRD4 gene variable number of tandem repeats (VNTR) and C-521T polymorphisms and human approach-related personality traits, including novelty seeking, extraversion, and impulsivity, restricted to adult samples recruited from nonpsychiatric populations, and extended on this literature by attempting to confirm any evidence of association in a replication sample (n = 309) selected for extreme scores on the extraversion subscale of the Eysenck Personality Questionnaire from a large (n = 40,090) population-based sample.

RESULTS

Our initial meta-analysis supported the association of the DRD4 C-521T polymorphism, but not the VNTR polymorphism, with approach-related traits. This conclusion was qualified by evidence of significant publication bias and the failure to detect association in a replication sample comprising individuals at the extremes of the trait distribution. The association of the C-521T polymorphism observed in our initial meta-analysis was robust to the inclusion of these new data, but our revised meta-analysis indicated that the association was present for measures of novelty seeking and impulsivity but not for measures of extraversion.

CONCLUSIONS

The DRD4 gene may be associated with measures of novelty seeking and impulsivity but not extraversion. The association of the C-521T variant with these measures, if genuine, may account for up to 3% of phenotypic variance.

Influences of parental rearing on the personality traits of healthy Japanese

Influences of parental rearing on the personality traits of healthy subjects were studied in 323 Japanese volunteers. Perceived parental rearing was assessed with the use of the Parental Bonding Instrument, which consists of the factors of care and protection, whereas personality traits were assessed with the use of the Temperament and Character Inventory, which has 7 dimensions. In male subjects, all personality dimensions except for novelty seeking were influenced by parental rearing; in female subjects, only the harm avoidance (HA) and self-directedness (SD) dimensions were affected by parenting. Paternal rearing influenced 3 dimensions in male subjects and 1 dimension in female subjects, whereas maternal rearing influenced 5 dimensions in male subjects and 2 dimensions in female subjects. In male subjects, higher HA was related to higher paternal protection (P < .05), whereas in female subjects, it was related to higher maternal protection (P < .01). In male subjects, lower SD was related to higher paternal protection (P < .05) and lower maternal care (P < .01), whereas in female subjects, it was related to lower paternal care (P < .05) and higher maternal protection (P < .01). These results suggest that parental rearing influences the personality traits of healthy subjects, especially HA and SD, with sex specificity in parents and recipients.

The Serotonin Receptor 2A Gene Moderates the Influence of Parental Socioeconomic Status on Adulthood Harm Avoidance

We examined whether the T102C polymorphism of the serotonin receptor 2A gene (HTR2A) moderated the influence of childhood or adolescence parental socioeconomic status (SES) on adulthood temperament trait harm avoidance (HA) in a population-based sample of 1246 healthy Finnish men and women, who were 24-39 years of age in the last follow-up phase. High parental SES predicted low adulthood HA. In addition, the C allele of the T102C polymorphism was associated with high HA in one of the two test settings, and with the mean of the two measurements. Most importantly, we found that the T102C polymorphism moderated the influence of parental SES, such that high parental SES predicted low adulthood HA in subjects with the T/T or T/C genotypes, while this was not true for those carrying the C/C genotype. The role of the T102C polymorphism was most pronounced among those with high parental SES. We conclude that the T102C polymorphism of the HTR2A gene may be involved in the development of temperament by moderating the influence of environmental conditions.

Food neophobia shows heritable variation in humans

Food neophobia refers to reluctance to eat unfamiliar foods. We determined the heritability of food neophobia in a family and a twin sample. The family sample consisted of 28 Finnish families (105 females, 50 males, aged 18-78 years, mean age 49 years) and the twin sample of 468 British female twin pairs (211 monozygous and 257 dizygous pairs, aged 17-82 years, mean age 55 years). Food neophobia was measured using the ten-item Food Neophobia Scale (FNS) questionnaire, and its internationally validated six-item modification. The heritability estimate for food neophobia was 69 and 66% in Finnish families (h(2)) and 67 and 66% in British female twins (a(2)+d(2)) using the ten- and six-item versions of the FNS, respectively. The results from both populations suggest that about two thirds of variation in food neophobia is genetically determined.

Future directions in behavioural syndromes research

A behavioural syndrome occurs when individuals behave in a consistent way through time or across contexts and is analogous to 'personality' or 'temperament'. Interest is accumulating in behavioural syndromes owing to their important ecological and evolutionary consequences. There are plenty of opportunities in this burgeoning young field to integrate proximate and functional approaches to studying behaviour, but there are few guidelines about where to start or how to design a study on behavioural syndromes. After summarizing what we do and do not know, this brief review aims to act as a general guide for studying behavioural syndromes. Although the array of possible behavioural combinations can seem overwhelming, there are at least four different strategies that can be used to choose which behaviours or contexts to study in a behavioural syndromes view. I describe the strengths and weaknesses of these non-exclusive strategies, and then discuss the methodological and statistical issues raised by such studies.

The ABC of demographic behaviour: how the interplays of alleles, brains, and contexts over the life course should shape research aimed at understanding population processes

This paper proposes core innovations in the strategy of research on demographic behaviour. One aim is a shift of attention away from events and towards a focus on dynamic processes and their interplay: away from a preoccupation with marriage and divorce, births, deaths, migrations, and household structure towards a broader perspective that takes account of partnership and intimacy, parenthood, potential and well-being, position in society and space, and personal ties. Another aim is a much closer engagement with genetics, neuroscience, psychology, and behavioural economics. A third aim is a strategy that pays more attention to pathways within the individual, to the processes entailed when the individual interacts with various contexts, and to progressions that involve the interplay of the pathways and processes through the life course. These shifts of emphasis, which have already begun to occur, require a systematic reassessment of priorities for research on demographic behaviour.

Tryptophan hydroxylase 1 gene haplotypes modify the effect of a hostile childhood environment on adulthood harm avoidance

We conducted a series of tests to determine whether there is any association between tryptophan hydroxylase 1 (TPH1) and temperament in adulthood. In addition to testing for main effects, we investigated whether TPH1 gene variation modifies the influence of childhood environment on temperament in adulthood. The subjects were 341 healthy adults whose childhood environment was assessed by their mothers in 1980 and who self-rated their temperaments twice, in 1997 and 2001. We found no association between the TPH1 gene and temperament; however, among women, the TPH1 gene modified a relationship between adverse childhood environment and harm avoidance in adulthood. This finding was confirmed in the same sample in another test setting 4 years later. The presence of the A/A haplotype of the TPH1 intron 7 A218A and A779C polymorphism predicted a high level of adulthood harm avoidance in the presence of a hostile childhood environment as defined in terms of emotional rejection, maternal neglect and harsh and inconsistent discipline. In addition, the findings suggest a gene-environment correlation for novelty seeking in men.

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.

Sexually dimorphic link between dopamine D2 receptor gene and neuroticism-anxiety

Prior theory-driven research probing the association between dopaminergic candidate genes and human personality has focused on the trait of novelty seeking. Here, we examined the association between the dopamine D2 receptor (DRD2) TaqI A polymorphism and two other personality traits, neuroticism-anxiety and agentic extraversion. We found no significant associations for agentic extraversion. However, for men, but not for women, we observed a strong and specific association between low neuroticism-anxiety and the A1+ allele of the DRD2 TaqI A polymorphism across two independent samples and across two alternative personality scales. We conclude that new theoretical models are needed to account for these and other recent reports of associations between neuroticism-anxiety and brain dopamine, which cannot be interpreted within the traditional framework.

Temperament and its role in developmental psychopathology

Temperament refers to early-appearing variation in emotional reactivity. The core dimensions of temperament and optimal method for assessment continue to be sources of considerable discussion. Nevertheless, the moderate stability of most temperamental traits and the strong influence of genetic and unique environmental factors have been well established, along with temperament's association with childhood psychiatric disorders. Both temperamental predisposition toward experiencing negative emotions and low inhibitory control are linked to many psychiatric conditions, while other dimensions, such as levels of extraversion, vary by, and likely even within, disorders. Accumulating research directed at understanding the mechanism of these links between temperament and psychopathology indicate that, at least for most disorders, the two constructs cannot be viewed as simply different points along a shared continuum. The effect of temperament upon psychopathology has been found to be mediated and moderated by a number of both internal and external factors. Additional research is needed to help further define the core dimensions of temperament and the complex mechanisms through which temperamental traits interact with other influences in affecting developmental trajectories.

Associations between temperament and DSM-IV externalizing disorders in children and adolescents

This study investigated associations between child temperament and DSM-IV disorders in children. A total of 156 probands (97 boys, 59 girls; mean age = 10.78 years) and 154 randomly selected siblings were assessed using the Junior Temperament and Character Inventory (JTCI) and a structured DSM-IV interview. Subjects were placed in nonoverlapping groups of (1) attention-deficit hyperactivity disorder (ADHD) only, (2) disruptive behavior disorders (DBD) only, (3) DBD plus an affective and/or anxiety disorder (DBD+Int), and (4) controls with no diagnosis. Many JTCI scales were found to differ between diagnostic groups and controls. Regression analyses showed independent associations between low persistence and ADHD-only group membership, high novelty seeking (NS), and the DBD-only group and between high harm avoidance (HA) and DBD+Int group membership. The interaction NS x HA was related to the ADHD-only group. Future research is needed to determine the mechanism of these association.

Maternal behavior modulates X-linked inheritance of behavioral coping in the defensive burying test

BACKGROUND

Complex behavioral traits such as coping strategies in response to stress are usually formed by genetic and environmental influences.

METHODS

By exploiting the phenotypic and genotypic differences between the Wistar Kyoto (WKY) and Fischer 344 (F344) inbred rat strains, we recently identified three X chromosome-linked quantitative trait loci contributing to differences in coping strategies in the defensive burying (DB) paradigm. In this article we study the influence of postnatal maternal environment in these behaviors by characterizing the maternal behavior of these strains and the effect of cross-fostering on DB behavior of male offspring from reciprocal crossing (F1).

RESULTS

Maternal behavior of WKY rats can be quantitatively characterized by less contact and more periods of neglect of their F1 pups. In contrast, F344 mothers engaged in more active behaviors such as licking/grooming and arched-back nursing. Cross-fostering male F1 pups at birth did not influence the latency to bury measure in DB; however, duration of burying and prod approaches were influenced by both genotype and maternal environment in an additive manner.

CONCLUSIONS

These results demonstrate that different measures of behavioral coping in the DB paradigm are influenced by maternal environment to differing degrees and in addition by genetic factors.