Two types of aggression are differentially related to serotonergic activity and the A779C TPH polymorphism

5-HTP inhibits eosinophilia via intracellular endothelial 5-HTRs; SNPs in 5-HTRs associate with asthmatic lung function

Background

Previous research showed that 5-hydroxytryptophan (5HTP), a metabolic precursor of serotonin, reduces allergic lung inflammation by inhibiting eosinophil migration across endothelial monolayers.

Objective

It is unknown if serotonin receptors are involved in mediating this 5HTP function or if serotonin receptor (HTR) single nucleotide polymorphisms (SNPs) associate with lung function in humans.

Methods

Serotonin receptor subtypes were assessed by qPCR, western blot, confocal microscopy, pharmacological inhibitors and siRNA knockdown. HTR SNPs were assessed in two cohorts.

Results

Pharmacological inhibition or siRNA knockdown of the serotonin receptors HTR1A or HTR1B in endothelial cells abrogated the inhibitory effects of 5HTP on eosinophil transendothelial migration. In contrast, eosinophil transendothelial migration was not inhibited by siRNA knockdown of HTR1A or HTR1B in eosinophils. Surprisingly, these HTRs were intracellular in endothelial cells and an extracellular supplementation with serotonin did not inhibit eosinophil transendothelial migration. This is consistent with the inability of serotonin to cross membranes, the lack of selective serotonin reuptake receptors on endothelial cells, and the studies showing minimal impact of selective serotonin reuptake inhibitors on asthma. To extend our HTR studies to humans with asthma, we examined the CHIRAH and GALA cohorts for HTR SNPs that affect HTR function or are associated with behavior disorders. A polygenic index of SNPs in HTRs was associated with lower lung function in asthmatics.

Conclusions

Serotonin receptors mediate 5HTP inhibition of transendothelial migration and HTR SNPs associate with lower lung function. These results may serve to aid in design of novel interventions for allergic inflammation.

Personality Traits and Family Environment: Antecedents of Child Aggression

Previous research reported significant relationship between Big Five personality traits and aggression in both adolescent’s and adult population. However, it is unclear about whether similar connection exist in early age. This study investigated how personality traits and family environment influence the development of aggression in school aged Saudi children. A sample of 315 school going children were recruited voluntarily to complete a set of measures examining Big Five personality factors, family environment and aggression. Correlation analysis were employed to evaluate association between Big Five personality traits, family environment and aggression. The results showed a significant relationship of Big Five personality factors and family environment factors to aggression. The findings of the study revealed that amongst the Big Five personality traits conscientiousness, agreeableness, and neuroticism were strongest antecedents of childhood aggression. Family environment characterized by family cohesion, expressiveness and conflict were appeared to be significant antecedents of aggressive behavior in children. This study expands our knowledge about the intervention strategies of aggression from Big Five traits and family environment perspectives.

The relationship of narcissism with tendency to react with anger and hostility: The roles of neuroticism and emotion regulation ability

The present study examined the relationship of grandiose and vulnerable narcissism with dispositional anger and hostility. We investigated the roles of neuroticism, emotional intelligence, and gender in this relationship, using a sample of 405 participants. The results indicated that vulnerable narcissism was associated with a higher tendency toward anger and hostility, and that neuroticism accounted for a large part of this association. Poor emotion managing, known as strategic emotion regulation ability, also played a role in hostility related to vulnerable narcissism, especially among men. When emotional stability was controlled for, grandiose narcissism showed links to anger and hostility. We concluded that high neuroticism and poor emotion regulation abilities among vulnerable narcissists contribute to increased anger/hostility, whereas emotional stability likely protects grandiose narcissists against these internal aspects of aggression. The significant relationships between both forms of narcissism with aggression, remaining after neuroticism and emotion regulation were accounted for, suggest that there is another underlying source of this link. Finally, we found that controlling for interindividual differences in neuroticism significantly increased the relationship between vulnerable and grandiose narcissism, suggesting the existence of the common core of narcissism.

Understanding the relationship between suicidality, current depressed mood, personality, and cognitive factors

OBJECTIVES

Links between suicidality and depressed mood are well established. There is, however, little information about the emotional regulation processes that underlie the relationship between suicidality and current low mood, and how these processes differ between groups of never-suicidal (NS), suicidal ideators, and suicide attempters. As suicidality and depression are heterogeneous constructs, this study aimed to conduct within- and between-group comparisons of known suicide risk factors that are associated with emotion regulation (neuroticism, trait aggression, brooding, impulsivity, and overgeneral autobiographical memories).

DESIGN

Correlational design using between- and within-group comparisons from self-report measures.

METHODS

Inter- and intragroup differences were identified using Pearson's correlation coefficients and tests of difference. An analysis of indirect effects was used to investigate whether the relationship between suicidality and current low mood was mediated by neuroticism, trait aggression, brooding, impulsivity, and overgeneral autobiographical memories, and if this relationship varied according to group type.

RESULTS

Brooding appeared to be a consistent feature of all three groups and was closely related to current low mood. Compared to the NS group, the relationship between suicide attempts and current low mood showed greater associations with brooding, trait aggression, and overgeneral autobiographical memories. Compared to the NS group, the suicidal ideation group showed stronger associations with neuroticism and impulsivity, but these factors did not correlate with low mood.

CONCLUSION

These results suggest a need for larger studies to focus on heterogeneity within suicidal populations and consider how different combinations of risk factors may heighten or reduce suicide risk.

PRACTITIONER POINTS

It is well known that the severity and intensity of suicide and depressed presentations vary because of underlying dispositional and contextual factors (Fried & Nesse, ) which, in turn, affect how events are interpreted and responded to. Despite this, there is little research about how these mechanisms operate in different types of suicide groups, and their influence on the relationship between suicidality and current low mood. Understanding interrelationships that affect current low mood is of clinical significance because past suicidal history and deteriorations in already negative mood are linked to repeated suicide attempts and completion. Our findings show that ruminative brooding, defined as a tendency to repeatedly think about emotional aspects of an event, consistently correlates with current low mood across different types of suicidal groups (NS, suicidal ideators, and suicide attempters), and across analyses. Findings also show that suicidal ideation and attempt groups were associated with specific personality characteristics that increased the propensity of emotional responding and interpretation compared to the NS group. The relationship between suicide attempt and current low mood had a higher propensity to be influenced by trait aggression, brooding, and overgenerality compared to the NS group. In contrast, although the suicidal ideation group correlated more strongly with neuroticism and impulsivity, these factors did not influence current low mood. In terms of clinical practice, these findings imply that specific styles of interpretation and thinking may maintain the relationship between suicidality and current low mood. Given the cross-sectional nature of the study, however, it is not possible to imply causality. Nevertheless, the findings obtained provide some support for transdiagnostic models of cognitive-behavioural processes that could be developed further.

Aggressive behavior in humans: Genes and pathways identified through association studies

Aggressive behavior has both genetic and environmental components. Many association studies have been performed to identify genetic factors underlying aggressive behaviors in humans. In this review we summarize the previous work performed in this field, considering both candidate gene (CGAS) and genome-wide association studies (GWAS), excluding those performed in samples where the primary diagnosis is a psychiatric or neurological disorder other than an aggression-related phenotype. Subsequently, we have studied the enrichment of pathways and functions in GWAS data. The results of our searches show that most CGAS have identified associations with genes involved in dopaminergic and serotonergic neurotransmission and in hormone regulation. On the other hand, GWAS have not yet identified genome-wide significant associations, but top nominal findings are related to several signaling pathways, such as axon guidance or estrogen receptor signaling, and also to neurodevelopmental processes and synaptic plasticity. Future studies should use larger samples, homogeneous phenotypes and standardized measurements to identify genes that underlie aggressive behaviors in humans. © 2016 Wiley Periodicals, Inc.

Effects of Gene × Attachment Interaction on Adolescents' Emotion Regulation and Aggressive Hostile Behavior Towards their Mothers during a Computer Game

Adolescence is a time of increased emotionality and major changes in emotion regulation often elicited in autonomy-relevant situations. Both genetic as well as social factors may lead to inter-individual differences in emotional processes in adolescence. We investigated whether both 5-HTTLPR and attachment security influence adolescents’ observed emotionality, emotional dysregulation, and their aggressive hostile autonomy while interacting with their mothers. Eighty-eight adolescents at age 12 were observed in interaction with their mothers during a standardized, emotion eliciting computer game task. They were genotyped for the 5-HTTLPR, a repeat polymorphism in the promoter region of the serotonin transporter gene. Concurrent attachment quality was assessed by the Late Childhood Attachment Interview (LCAI). Results revealed a significant gene × attachment effect showing that ss/sl carriers of 5-HTTLPR show increased emotional dysregulation and aggressive hostile autonomy towards their mothers. The results of the study suggest that secure attachment in adolescence moderates the genetically based higher tendency for emotional dysregulation and aggressive reactions to restrictions of autonomy during emotional social interactions with their mothers.

Genetics of aggressive behavior: An overview

The Research Domain Criteria (RDoC) address three types of aggression: frustrative non-reward, defensive aggression and offensive/proactive aggression. This review sought to present the evidence for genetic underpinnings of aggression and to determine to what degree prior studies have examined phenotypes that fit into the RDoC framework. Although the constructs of defensive and offensive aggression have been widely used in the animal genetics literature, the human literature is mostly agnostic with regard to all the RDoC constructs. We know from twin studies that about half the variance in behavior may be explained by genetic risk factors. This is true for both dimensional, trait-like, measures of aggression and categorical definitions of psychopathology. The non-shared environment seems to have a moderate influence with the effects of shared environment being unclear. Human molecular genetic studies of aggression are in an early stage. The most promising candidates are in the dopaminergic and serotonergic systems along with hormonal regulators. Genome-wide association studies have not yet achieved genome-wide significance, but current samples are too small to detect variants having the small effects one would expect for a complex disorder. The strongest molecular evidence for a genetic basis for aggression comes from animal models comparing aggressive and non-aggressive strains or documenting the effects of gene knockouts. Although we have learned much from these prior studies, future studies should improve the measurement of aggression by using a systematic method of measurement such as that proposed by the RDoC initiative.

Does Marriage Moderate Genetic Effects on Delinquency and Violence?

Using data from the National Longitudinal Study of Adolescent to Adult Health (N = 1,254), the authors investigated whether marriage can foster desistance from delinquency and violence by moderating genetic effects. In contrast to existing gene-environment research that typically focuses on one or a few genetic polymorphisms, they extended a recently developed mixed linear model to consider the collective influence of 580 single nucleotide polymorphisms in 64 genes related to aggression and risky behavior. The mixed linear model estimates the proportion of variance in the phenotype that is explained by the single nucleotide polymorphisms. The authors found that the proportion of variance in delinquency/violence explained was smaller among married individuals than unmarried individuals. Because selection, confounding, and heterogeneity may bias the estimate of the Gene × Marriage interaction, they conducted a series of analyses to address these issues. The findings suggest that the Gene × Marriage interaction results were not seriously affected by these issues.

Revisiting the serotonin-aggression relation in humans: a meta-analysis

The inverse relation between serotonin and human aggression is often portrayed as "reliable," "strong," and "well established" despite decades of conflicting reports and widely recognized methodological limitations. In this systematic review and meta-analysis, we evaluate the evidence for and against the serotonin deficiency hypothesis of human aggression across 4 methods of assessing serotonin: (a) cerebrospinal fluid levels of 5-hydroxyindoleacetic acid (CSF 5-HIAA), (b) acute tryptophan depletion, (c) pharmacological challenge, and (d) endocrine challenge. Results across 175 independent samples and over 6,500 total participants were heterogeneous, but, in aggregate, revealed a small, inverse correlation between serotonin functioning and aggression, anger, and hostility (r = -.12). Pharmacological challenge studies had the largest mean weighted effect size (r = -.21), and CSF 5-HIAA studies had the smallest (r = -.06). Potential methodological and demographic moderators largely failed to account for variability in study outcomes. Notable exceptions included year of publication (effect sizes tended to diminish with time) and self- versus other-reported aggression (other-reported aggression was positively correlated to serotonin functioning). We discuss 4 possible explanations for the pattern of findings: unreliable measures, ambient correlational noise, an unidentified higher order interaction, and a selective serotonergic effect. Finally, we provide 4 recommendations for bringing much needed clarity to this important area of research: acknowledge contradictory findings and avoid selective reporting practices; focus on improving the reliability and validity of serotonin and aggression measures; test for interactions involving personality and/or environmental moderators; and revise the serotonin deficiency hypothesis to account for serotonin's functional complexity.

Acute responsivity of the serotonergic system to S-citalopram and positive emotionality-the moderating role of the 5-HTTLPR

According to the idea that the central serotonergic system has a modulatory function on behavior and personality in general, we aimed to highlight its association to habitual positive emotionality. In a placebo-controlled double-blind and randomized cross-over neuroendocrine challenge design (n = 72 healthy males) we investigated the association of the central serotonergic responsivity, 5-HTTLPR-genotype as well as their combined effects on positive emotionality. Regression analyses revealed an involvement of the serotonergic system in positive emotionality. There was, however, no direct association between positive emotionality and cortisol responses to S-citalopram; rather 5-HTTLPR-genotype showed an association (p < 0.05). That is, positive emotionality scores increased with the number of s-alleles carried by the individuals. Most notable was the moderating role of 5-HTTLPR-genotype (p < 0.05) on the association between acute serotonergic responsivity and positive emotionality. Indeed, this association was only found in ss-homozygotes, in which the acute responsivity of the serotonergic system additionally seems to contribute to the level of positive emotionality (r = 0.70, p < 0.05). The findings correspond to previous research demonstrating that the 5-HTTLPR is not only involved in the negative-emotional aspects of behavior and temperament, but is associated, moreover, with positive affectivity-supporting the assumption of its valence-neutrality. In addition, our data are in line with the idea of possible influences of the 5-HTTLPR-genotype on early neuronal development. They also indicate the need for further studies in order to clearly elucidate the role of the serotonergic system and its subcomponents in the regulation of positive emotionality.

The role of the serotonergic system at the interface of aggression and suicide

Alterations in serotonin (5-HT) neurochemistry have been implicated in the aetiology of all major neuropsychiatric disorders, ranging from schizophrenia to mood and anxiety-spectrum disorders. This review will focus on the multifaceted implications of 5-HT-ergic dysfunctions in the pathophysiology of aggressive and suicidal behaviours. After a brief overview of the anatomical distribution of the 5-HT-ergic system in the key brain areas that govern aggression and suicidal behaviours, the implication of 5-HT markers (5-HT receptors, transporter as well as synthetic and metabolic enzymes) in these conditions is discussed. In this regard, particular emphasis is placed on the integration of pharmacological and genetic evidence from animal studies with the findings of human experimental and genetic association studies. Traditional views postulated an inverse relationship between 5-HT and aggression and suicidal behaviours; however, ample evidence has shown that this perspective may be overly simplistic, and that such pathological manifestations may reflect alterations in 5-HT homoeostasis due to the interaction of genetic, environmental and gender-related factors, particularly during early critical developmental stages. The development of animal models that may capture the complexity of such interactions promises to afford a powerful tool to elucidate the pathophysiology of impulsive aggression and suicidability, and identify new effective therapies for these conditions.

Interaction between tryptophan hydroxylase I polymorphisms and childhood abuse is associated with increased risk for borderline personality disorder in adulthood

INTRODUCTION

Borderline personality disorder (BPD) is a severe disorder with high morbidity and mortality, but unknown etiology. Childhood abuse has been proposed as an etiological factor, but the mechanism by which an abuse history could influence the risk for BPD has not been determined. The aim of this study was to determine whether the tryptophan hydroxylase 1 (TPH1) gene is related to BPD in a clinical sample, and whether TPH1 genotypes or haplotypes moderate the relationship between abuse history and BPD.

METHODS

Three hundred and ninety-eight patients diagnosed with mood disorders were genotyped for TPH1 G-6526A promoter polymorphism (rs4537731) and the A218C intron 7 polymorphism (rs1800532) and a set of ancestry informative markers, assessed for Diagnostic and Statistical Manual of Mental Disorders, 4th edition diagnoses, and assessed for a history of physical and sexual abuse.

RESULTS

Patients with a diagnosis of BPD were more likely to be risk allele carriers (A alleles at both loci) than the non-BPD group. Logistic regression analysis predicting BPD diagnosis with both single-nucleotide polymorphisms and haplotypes showed significant interaction effects between genotype and abuse history. Poisson regression predicting the number of BPD diagnostic criteria met with the same predictor set also included a significant interaction term. Risk allele carriers with a history of abuse had an increased likelihood of a BPD diagnosis.

CONCLUSION

Variation in TPH1 may increase risk for developing BPD as a result of childhood abuse. Elements of BPD pathology may be due in part to a genetically influenced serotonergic dysfunction, which in turn may lead to a differential response to environmental stressors.

Inhibition of allergic inflammation by supplementation with 5-hydroxytryptophan

Clinical reports indicate that patients with allergy/asthma commonly have associated symptoms of anxiety/depression. Anxiety/depression can be reduced by 5-hydroxytryptophan (5-HTP) supplementation. However, it is not known whether 5-HTP reduces allergic inflammation. Therefore, we determined whether 5-HTP supplementation reduces allergic inflammation. We also determined whether 5-HTP decreases passage of leukocytes through the endothelial barrier by regulating endothelial cell function. For these studies, C57BL/6 mice were supplemented with 5-HTP, treated with ovalbumin fraction V (OVA), house dust mite (HDM) extract, or IL-4, and examined for allergic lung inflammation and OVA-induced airway responsiveness. To determine whether 5-HTP reduces leukocyte or eosinophil transendothelial migration, endothelial cells were pretreated with 5-HTP, washed and then used in an in vitro transendothelial migration assay under laminar flow. Interestingly, 5-HTP reduced allergic lung inflammation by 70-90% and reduced antigen-induced airway responsiveness without affecting body weight, blood eosinophils, cytokines, or chemokines. 5-HTP reduced allergen-induced transglutaminase 2 (TG2) expression and serotonylation (serotonin conjugation to proteins) in lung endothelial cells. Consistent with the regulation of endothelial serotonylation in vivo, in vitro pretreatment of endothelial cells with 5-HTP reduced TNF-α-induced endothelial cell serotonylation and reduced leukocyte transendothelial migration. Furthermore, eosinophil and leukocyte transendothelial migration was reduced by inhibitors of transglutaminase and by inhibition of endothelial cell serotonin synthesis, suggesting that endothelial cell serotonylation is key for leukocyte transendothelial migration. In summary, 5-HTP supplementation inhibits endothelial serotonylation, leukocyte recruitment, and allergic inflammation. These data identify novel potential targets for intervention in allergy/asthma.

Modeling borderline personality disorder based on the neurobehavioral foundation of major personality traits

Borderline personality disorder (BPD) is an exceedingly complex behavioral phenomenon that is in need of conceptual clarification within a larger model of personality disorders (PDs). The association of personality traits to BPD is discussed initially as a means of introducing a dimensional personality approach to understanding BPD. While this model suggests that PDs emerge at the extremes of personality dimensions, attempts to demonstrate such an association have been empirically disappointing and conceptually unilluminating. Therefore, in this article, we attempt to extend such models by outlining the neurobehavioral systems that underlie major personality traits, and highlight the evidence that they are subject to experience-dependent modification that can be enduring through effects on genetic expression, mainly through processes known as epigenetics. It is through such processes that risk for personality disorder may be modified by experience at any point in development, but perhaps especially during early critical periods of development. We conclude by presenting a multidimensional model of PDs, in general, and BPD, in particular, that relies on the concepts developed earlier in the article. Our goal is to provide a guide for novel clinical conceptualization and assessment of PDs, as well as research on their psychobiological nature and pharmacological treatment.

An fMRI study on the role of serotonin in reactive aggression

Reactive aggression after interpersonal provocation is a common behavior in humans. Little is known, however, about brain regions and neurotransmitters critical for the decision-making and affective processes involved in aggressive interactions. With the present fMRI study, we wanted to examine the role of serotonin in reactive aggression by means of an acute tryptophan depletion (ATD). Participants performed in a competitive reaction time task (Taylor Aggression Paradigm, TAP) which entitled the winner to punish the loser. The TAP seeks to elicit aggression by provocation. The study followed a double-blind between-subject design including only male participants. Behavioral data showed an aggression diminishing effect of ATD in low trait-aggressive participants, whereas no ATD effect was detected in high trait-aggressive participants. ATD also led to reduced insula activity during the decision phase, independently of the level of provocation. Whereas previous reports have suggested an inverse relationship between serotonin level and aggressive behavior with low levels of serotonin leading to higher aggression and vice versa, such a simple relationship is inconsistent with the current data.

Interaction of 5-HTTLPR genotype and unipolar major depression in the emergence of aggressive/hostile traits

OBJECTIVE

The 5-HTTLPR polymorphism has been associated both with depression and aggression/hostility. The multidirectional association between depression, aggression and the s allele may be important, since all these phenomena are related to suicidal behavior. Our aim was to investigate the association between 5-HTTLPR and aggressive/hostile traits in depressed patients and controls.

METHODS

137 depressive and 118 control women completed the Buss-Durkee Hostility Inventory and were genotyped for 5-HTTLPR. BDHI scores in the different groups were investigated by Generalized Linear Model Analysis. Association between dependent and independent variables in the model was tested by the likelihood ratio Chi-square statistic.

RESULTS

Diagnosis and genotype showed a significant association with several aggressive/hostile traits. Interaction of the two main effects was also significant in case of several subscales. Post hoc analyses indicated a significant association between BDHI subscales and s allele only in the depressed group.

LIMITATION

Only women were studied and since gender differences are present both in aggressive behavior and putatively in the behavioral effects of 5-HTTLPR genotype, our findings pertain only to females.

CONCLUSION

Our results indicate a robust relationship between aggression/hostility and 5-HTTLPR genotype, but this association is more marked in the presence of depression. The presence of the s allele thus not only contributes to a higher risk of depression, but in depressives also leads to higher aggression/hostility. Our results have important implications for suicide research, since the s allele is associated with violent suicide, and this association may be mediated through the emergence of increased aggression/hostility in depressed patients carrying the s allele.

Neurogenetic and experiential processes underlying major personality traits: implications for modelling personality disorders

Abstract The association of personality traits to personality disorders (PDs) is assumed by many to fit a dimensional model, where PDs emerge at the extremes of personality dimensions. Nevertheless, attempts to demonstrate such an association have been empirically disappointing and conceptually unilluminating. In this article we attempt to extend such models by outlining the neurobehavioural systems that underlie major personality traits, and highlight the evidence that they are subject to experience-dependent modification that can be enduring through effects on genetic expression, mainly through processes known as epigenetics. It is through such processes that risk for personality disorder may be modified by experience at any point in development, but perhaps especially during early critical periods of development. We conclude by presenting a novel multidimensional model of PDs that relies on the concepts developed earlier in the article. Our goal is to provide a guide for research on the psychobiological nature and pharmacological treatment of PDs.

Behavioral and pharmacogenetics of aggressive behavior

Serotonin (5-HT) has long been considered as a key transmitter in the neurocircuitry controlling aggression. Impaired regulation of each subtype of 5-HT receptor, 5-HT transporter, synthetic and metabolic enzymes has been linked particularly to impulsive aggression. The current summary focuses mostly on recent findings from pharmacological and genetic studies. The pharmacological treatments and genetic manipulations or polymorphisms of aspecific target (e.g., 5-HT1A receptor) can often result in inconsistent results on aggression, due to "phasic" effects of pharmacological agents versus "trait"-like effects of genetic manipulations. Also, the local administration of a drug using the intracranial microinjection technique has shown that activation of specific subtypes of 5-HT receptors (5-HT1A and 5-HT1B) in mesocorticolimbic areas can reduce species-typical and other aggressive behaviors, but the same receptors in the medial prefrontal cortex or septal area promote escalated forms of aggression. Thus, there are receptor populations in specific brain regions that preferentially modulate specific types of aggression. Genetic studies have shown important gene-environment interactions; it is likely that the polymorphisms in the genes of 5-HT transporters or rate-limiting synthetic and metabolic enzymes of 5-HT (e.g., MAOA) determine the vulnerability to adverse environmental factors that escalate aggression. We also discuss the interaction between the 5-HT system and other systems. Modulation of 5-HT neurons in the dorsalraphe nucleus by GABA, glutamate and CRF profoundly regulate aggressive behaviors. Also, interactions of the 5-HT system with other neuropeptides(arginine vasopressin, oxytocin, neuropeptide Y, opioid) have emerged as important neurobiological determinants of aggression. Studies of aggression in genetically modified mice identified several molecules that affect the 5-HT system directly (e.g., Tph2, 5-HT1B, 5-HT transporter, Pet1, MAOA) or indirectly[e.g., BDNF, neuronal nitric oxide (nNOS), aCaMKII, Neuropeptide Y].The future agenda delineates specific receptor subpopulations for GABA, glutamate and neuropeptides as they modulate the canonical aminergic neurotransmitters in brainstem, limbic and cortical regions with the ultimate outcome of attenuating or escalating aggressive behavior.

Neural mechanisms of the testosterone-aggression relation: the role of orbitofrontal cortex

Testosterone plays a role in aggressive behavior, but the mechanisms remain unclear. The present study tested the hypothesis that testosterone influences aggression through the OFC, a region implicated in self-regulation and impulse control. In a decision-making paradigm in which people chose between aggression and monetary reward (the ultimatum game), testosterone was associated with increased aggression following social provocation (rejecting unfair offers). The effect of testosterone on aggression was explained by reduced activity in the medial OFC. The findings suggest that testosterone increases the propensity toward aggression because of reduced activation of the neural circuitry of impulse control and self-regulation.

The relationship between basal and acute HPA axis activity and aggressive behavior in adults

The hypothalamic-pituitary-adrenal (HPA) axis seems to play a major role in the development, elicitation, and enhancement of aggressive behavior in animals. Increasing evidence suggests that this is also true for humans. However, most human research on the role of the HPA axis in aggression has been focusing on highly aggressive children and adolescent clinical samples. Here, we report on a study of the role of basal and acute HPA axis activity in a sample of 20 healthy male and female adults. We used the Taylor Aggression Paradigm to induce and measure aggression. We assessed the cortisol awakening response as a trait measure of basal HPA axis activity. Salivary free cortisol measures for the cortisol awakening response were obtained on three consecutive weekdays immediately following awakening and 30, 45, and 60 min after. Half of the subjects were provoked with the Taylor Aggression Paradigm to behave aggressively; the other half was not provoked. Acute HPA axis activity was measured four times, once before and three times after the induction of aggression. Basal cortisol levels were significantly and negatively related to aggressive behavior in the provoked group and explained 67% of the behavioral variance. Cortisol levels following the induction of aggression were significantly higher in the provoked group when baseline levels were taken into account. The data implicate that the HPA axis is not only relevant to the expression of aggressive behavior in clinical groups, but also to a large extent in healthy ones.

Is desire for social relationships mediated by the serotonergic system in the prefrontal cortex? An [(18)F]setoperone PET study

Social behavior and desire for social relationships have been independently linked to the serotonergic system, the prefrontal cortex, especially the orbitofrontal cortex (OFC), and the anterior cingulate cortex (ACC). The goal of this study was to explore the role of serotonin 5HT(2A) receptors in these brain regions in forming and maintaining close interpersonal relationships. Twenty-four healthy subjects completed the Temperament and Character Inventory (TCI) prior to undergoing [(18)F]setoperone brain positron emission tomography (PET) to measure serotonin 5HT(2A) receptor availability within the OFC (BA 11 and 47) and ACC (BA 32). We explored the relationship between desire for social relationships, as measured by the TCI reward dependence (RD) scale, and 5HT(2A) receptor non-displaceable binding potential (BP(nd)) in these regions. Scores of RD were negatively correlated with 5HT(2A) BP(nd) in the ACC (BA 32, r = -.528, p = .012) and OFC (BA 11, r = -.489, p = .021; BA 47, r = -.501, p = .017). These correlations were corroborated by a voxel-wise analysis. These results suggest that the serotonergic system may have a regulatory effect on the OFC and ACC for establishing and maintaining social relationships.

Behavioral genetics in antisocial spectrum disorders and psychopathy: a review of the recent literature

Behavioral geneticists are increasingly using the tools of molecular genetics to extend upon discoveries from twin, family, and adoption studies concerning the heritability of antisocial spectrum disorders and psychopathy. While there is a substantial body of research concerning antisocial spectrum disorders in the behavioral genetics literature, only a few studies could be located using the phenotype of psychopathy. In this report we summarize some of the recent molecular genetics work concerning antisocial spectrum disorders and psychopathy, with a focus on genes involved in the serotonergic and dopaminergic pathways, while also mentioning some of the novel genetic factors being considered. Monoamine oxidase (MAOA) and the serotonin transporter (5HTT) are reviewed at length, as these genes have received significant scientific attention in recent years and are sites of high biological plausibility in antisocial spectrum disorders and psychopathy.

[Neurobiological aspects of reactive and proactive violence in antisocial personality disorder and "psychopathy"]

Impulsive-reactive violent offenders show increased autonomic activity in response to negative emotional and threatening stimuli. A volume reduction and/or activity decrease of frontal brain structures associated with impulse control and the regulation of fear and anger are likewise found in combination with a fear-related hyperactivity of the amygdala. In addition, impulsive aggression is facilitated by variants of gene polymorphisms influencing the serotonergic system. Conversely, proactive-instrumental violent offender with psychopathy, who are characterized by a lack of empathy and remorse, demonstrate an autonomic hypo-responsivity as well as dysfunctions of the amygdala and of cortical regions related to empathic and social behavior. Developmentally, aggressive children exhibit temperamental differences from early childhood on that are characteristic of a developmental pathway towards either reactive or proactive violence later in life. Exposure to negative environmental factors like ineffective parenting or childhood maltreatment has been related to a heightened risk for developing reactive violence. A developmental trajectory of proactive violence, however, has been related to a mostly genetically determined callous unemotional temperament of the child that disrupts the parental socialization efforts during childhood.

Genetic and attachment influences on adolescents' regulation of autonomy and aggressiveness

BACKGROUND

Adolescence is a time when intense emotions are elicited within the parent-adolescent relationship, often when autonomy subjectively is endangered. As emotion dysregulation is one of the risk processes for the development of psychopathology, adolescence may be perceived as a highly sensitive period for maladjustment. Inter-individual differences in emotionality and emotion regulation have been shown to be influenced or moderated by molecular genetic differences in the serotonin transporter gene (5-HTT) and by attachment patterns. We investigated whether both the 5-HTT and attachment are associated with emotionality and emotion regulation in an observed adolescent-mother interaction and the personality traits aggressiveness and anxiety in adolescence.

METHODS

Ninety-one adolescents at age 12 were observed in interaction with their mothers during a standardized emotion-eliciting social task to assess emotionality and emotion regulation in relation to autonomy. Adolescents' aggressiveness and anxiety were assessed by mother report. Concurrent attachment quality was determined by an attachment interview. DNA samples were collected in order to assess the 5-HTTLPR, a repeat polymorphism in the promoter region of the serotonin transporter gene.

RESULTS

While the short allele of the serotonin transporter gene was associated with a higher overall rate of autonomy behaviors, attachment security was related to more agreeable and less hostile autonomy. A significant interaction revealed a moderating effect of attachment security. Carriers of the short version of the 5-HTTLPR showed more agreeable autonomy when they had a secure attachment behavior strategy but showed more hostile autonomy when they were insecurely attached. Carriers of the short version of the 5-HTTLPR and insecurely attached adolescents were rated as more aggressive.

CONCLUSIONS

The study suggests a gene-attachment interaction in adolescents where the adolescent's attachment status moderates a genetically based higher negative reactivity in response to threats to autonomy in social interactions.

Genetic, environmental, and epigenetic factors in the development of personality disturbance

A dimensional model of personality disturbance is presented that is defined by extreme values on interacting subsets of seven major personality traits. Being at the extreme has marked effects on the threshold for eliciting those traits under stimulus conditions: that is, the extent to which the environment affects the neurobiological functioning underlying the traits. To explore the nature of development of extreme values on these traits, each trait is discussed in terms of three major issues: (a) the neurobiological variables associated with the trait, (b) individual variation in this neurobiology as a function of genetic polymorphisms, and (c) the effects of environmental adversity on these neurobiological variables through the action of epigenetic processes. It is noted that gene–environment interaction appears to be dependent on two main factors: (a) both genetic and environmental variables appear to have the most profound and enduring effects when they exert their effects during early postnatal periods, times when the forebrain is undergoing exuberant experience–expectant dendritic and axonal growth; and (b) environmental effects on neurobiology are strongly modified by individual differences in “traitlike” functioning of neurobiological variables. A model of the nature of the interaction between environmental and neurobiological variables in the development of personality disturbance is presented.

The tryptophan hydroxylase-1 A218C polymorphism is associated with diagnosis, but not suicidal behavior, in borderline personality disorder

While there is some preliminary evidence that the tryptophan hydroxylase I (TPH1) polymorphisms are related to Borderline Personality Disorder (BPD), it is not clear if this association is due to the high rates of suicidal behavior in this patient group. Because of the reported association between TPH1 polymorphisms and suicidal behavior, determining whether TPH1 is related to BPD independent of suicidal behavior is of particular importance. One hundred patients diagnosed with BPD and 101 healthy controls were genotyped for TPH1 intron 7 A218C polymorphism and assessed for impulsiveness and hostility. The BPD patient group had a higher frequency of A allele carriers (AA/AC genotypes) than the control group (chi(2) = 6.12, df = 1, P = 0.01), and differed by genotype frequencies (P = 0.03). Suicide attempter status in the patient group was not related to genotype. Logistic regression analysis controlling for age and gender predicted BPD diagnosis from TPH1 allele group (AA/AC vs. CC, P = 0.03), and TPH1 heterozygotes (AC) appeared to have the highest risk for BPD (P = 0.03). In the full sample, participants with the AC genotype had higher impulsiveness and hostility scores. However, TPH1 did not predict these traits in either of the groups independently, suggesting the association may be an artifact of the association between TPH1 and BPD. Results suggest that the A allele of the tryptophan hydroxylase-1 A218 polymorphism may be associated with BPD, and that it does not appear to be related to suicidal behavior in this population. An aspect of BPD pathology may be due to serotonergic dysfunction.

Y haplogroups and aggressive behavior in a Pakistani ethnic group

Studies show that personality dimensions such as aggression are influenced by genetic factors and that allelic variants located on the Y chromosome influence such behavior. We investigated polymorphisms on the male-specific region of the human Y chromosome in 156 unrelated males from the same ethnic background, who were administered the Punjabi translation of the Buss and Perry Aggression Questionnaire that measures four aspects that constitute aggressive behavior, i.e. physical aggression, verbal aggression, anger, and hostility. A value of .85 for Cronbach's coefficient alpha indicates considerable internal consistency and suggests that the psychometric properties of the aggression questionnaire can be adapted for the Pakistani population. A mean score+/-SD of 69.70+/-19.95 was obtained for the questionnaire. Each individual was genotyped following a phylogenetic hierarchical approach to define evolutionary Y haplogroups. Five Y haplogroups that are commonly found in Eurasia and Pakistan comprised 87% (n=136) of the population sample, with one haplogroup, R1a1, constituting 55% of the sampled population. A comparison of the total and four subscale mean scores across the five common Y haplogroups that were present at a frequency > or =3% in this ethnic group revealed no overall significant differences. However, effect-size comparisons allowed us to detect an association of the haplogroups R2 (Cohen's d statistic=.448-.732) and R1a1 (d=.107-.448) with lower self-reported aggression mean scores in this population.

Reliability reporting across studies using the Buss Durkee Hostility Inventory

Empirical research on anger and hostility has pervaded the academic literature for more than 50 years. Accurate measurement of anger/hostility and subsequent interpretation of results requires that the instruments yield strong psychometric properties. For consistent measurement, reliability estimates must be calculated with each administration, because changes in sample characteristics may alter the scale's ability to generate reliable scores. Therefore, the present study was designed to address reliability reporting practices for a widely used anger assessment, the Buss Durkee Hostility Inventory (BDHI). Of the 250 published articles reviewed, 11.2% calculated and presented reliability estimates for the data at hand, 6.8% cited estimates from a previous study, and 77.1% made no mention of score reliability. Mean alpha estimates of scores for BDHI subscales generally fell below acceptable standards. Additionally, no detectable pattern was found between reporting practices and publication year or journal prestige. Areas for future research are also discussed.

Serotonergic function, two-mode models of self-regulation, and vulnerability to depression: what depression has in common with impulsive aggression

Evidence from diverse literatures supports the viewpoint that two modes of self-regulation exist, a lower-order system that responds quickly to associative cues of the moment and a higher-order system that responds more reflectively and planfully; that low serotonergic function is linked to relative dominance of the lower-order system; that how dominance of the lower-order system is manifested depends on additional variables; and that low serotonergic function therefore can promote behavioral patterns as divergent as impulsive aggression and lethargic depression. Literatures reviewed include work on two-mode models; studies of brain function supporting the biological plausibility of the two-mode view and the involvement of serotonergic pathways in functions pertaining to it; and studies relating low serotonergic function to impulsiveness, aggression (including extreme violence), aspects of personality, and depression vulnerability. Substantial differences between depression and other phenomena reviewed are interpreted by proposing that depression reflects both low serotonergic function and low reward sensitivity. The article closes with brief consideration of the idea that low serotonergic function relates to even more diverse phenomena, whose natures depend in part on sensitivities of other systems.

Preliminary evidence that specific candidate genes are associated with adolescent-onset antisocial behavior

Though initially conceptualized as resulting from peer imitation of child-onset or life-course-persistent youth [Moffitt, 1993], there is mounting evidence from twin studies that adolescent-onset or adolescent-limited antisocial behavior may also be genetically influenced. This study sought to provide preliminary molecular genetic evidence in support of these findings. We further evaluated whether genetic associations varied between behavioral subtypes of ASB (i.e., physical aggression and nonaggressive rule-breaking), given that only the latter has been found to characterize adolescent-onset ASB. The sample consisted of 211 undergraduate men of European-American ancestry. Three polymorphisms with theoretical and/or empirical ties to ASB or related traits (i.e., tryptophan hydroxylase-A218C, 5HT(2A) His452Tyr, and the DAT1 variable nucleotide tandem repeat) were genotyped. Analyses revealed that two of the three polymorphisms (i.e., His452Tyr and DAT1) were associated with adolescent ASB. Moreover, these associations appeared to be specific to the nonaggressive, rule-breaking form of ASB, and did not extend to physical aggression, further supporting ties to adolescent ASB in particular. Such results thus constructively replicate earlier findings of genetic influence on adolescent ASB. They also offer preliminary evidence that the genetic processes underlying aggressive and nonaggressive antisocial behavior may be (at least partially) distinct.

Stress, genes and the biology of suicidal behavior

Suicidal behavior is partly heritable. Studies seeking the responsible candidate genes have examined genes involved in neurotransmitter systems shown to have altered function in suicide and attempted suicide. These neurotransmitter systems include the serotonergic, noradrenergic, and dopaminergic systems and the hypothalamic-pituitary-adrenal axis. With some exceptions, most notably the serotonin transporter gene promoter polymorphism (HTTLPR), replication of candidate gene association studies findings has been difficult. This article reviews current knowledge of specific gene effects and gene-environment interactions that influence risk for suicidal behavior. Effects of childhood stress on development and how it influences adult responses to current stress are shown to be relevant for mood disorders, aggressive/impulsive traits, and suicidal behavior.

Long-term citalopram maintenance in mice: selective reduction of alcohol-heightened aggression

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) alleviate many affective disturbances in human clinical populations and are used in animal models to study the influence of serotonin (5-HT) on aggressive behavior and impulsivity.

OBJECTIVE

We hypothesized that long-term SSRI treatment may reduce aggressive behavior escalated by alcohol consumption in mice. Therefore, aggression was tested in male CFW mice to determine whether repeated citalopram (CIT) administration reduces alcohol-heightened aggression.

MATERIALS AND METHODS

Resident male mice self-administered alcohol by performing an operant response on a panel placed in their home cage that delivered a 6% alcohol solution. Mice repeatedly confronted an intruder 15 min after self-administration of either 1 g/kg alcohol (EtOH) or water (H(2)O). Aggressive behaviors were higher in most mice when tests occurred after EtOH intake relative to H(2)O. Once baseline aggression was established, animals were injected (i.p.) twice daily with 10 mg/kg CIT or saline (SAL) for 32 days. Every 4 days throughout the CIT treatment period, aggressive encounters occurred 6 h after CIT injections, with testing conditions alternating between EtOH and H(2)O intake.

RESULTS

Aggression was only modestly affected by CIT in the first 2 weeks of treatment. However, by day 17 of CIT treatment, alcohol-heightened aggressive behavior was abolished, while baseline aggression remained stable. These data lend support for the role of the 5-HT transporter in the control of alcohol-related aggressive behavior, and the time course of effects suggests that a change in density of 5HT(1A) autoreceptors is necessary before antidepressant drugs produce beneficial outcomes.

Association between monoamine oxidase A polymorphisms and anger-related personality traits in Korean women

It has been suggested that polymorphisms in the monoamine oxidase A (MAO-A) gene are associated with aggressive and impulsive behaviors. In the present study, we investigated the association of the MAO-A variable number of tandem repeat polymorphism in the promoter region (MAO-A uVNTR) with anger-related personality traits. Specifically, MAO-A uVNTR polymorphisms were examined for associations with the State-Trait Anger Expression Inventory (STAXI) scores in 211 normal Korean women. All subjects were assessed using the STAXI and genotyped for MAO-A uVNTR status. The scores on the STAXI subscales differed significantly among the MAO-A uVNTR polymorphism genotypes in terms of anger expression-out (AX-Out) scores. Post hoc comparisons revealed significant differences between the 3/3 and 4/4, and between 3/4 and 4/4 polymorphisms. However, no significant difference was observed in other STAXI subscale scores among these genotypes. Subjects with the high-activity MAO-A uVNTR had significantly higher AX-Out scores than subjects with other genotypes. MAO-A uVNTR polymorphisms may contribute in part to the expression of anger. These findings support the hypothesis that this polymorphism in the MAO-A gene may be associated with anger-related personality traits in Korean women.

The role of the TPH1 and TPH2 genes for nicotine dependence: a genetic association study in two different age cohorts

Based on pharmacological and genetic studies suggesting a role of the serotonergic system for nicotine dependence, two genetic variants, one on the tryptophan hydroxylase 1 (TPH1) and one on the TPH2 gene, were investigated. The TPH2 -703G/T promoter polymorphism was associated with smoking status and age of smoking onset in two independent Caucasian samples of different age cohorts. Sample 1 consisted of 3,602 subjects of a population-based cohort study of whom 95% were 40-65 years old, and sample 2 consisted of 723 subjects in the twenties. The TPH1 779A/C was only investigated in sample 2 where additional data with respect to the degree of nicotine dependence were assessed. Results yield support for previous findings of an association between the AA genotype of TPH1 779A/C and nicotine status and a tendency for a heterosis effect with respect to the degree of nicotine dependence. The TPH2 -703G/T was significantly associated with age of smoking onset in both samples. The interaction between the T allele and gender was significant in both samples. Carriers of the GG genotype started significantly earlier to smoke than carriers with a T allele. In the older cohort, age of onset was earlier in carriers of the GG genotype only in men, and in the younger cohort the GG genotype predisposes only women to start smoking earlier in life. This interaction could constitute a gene-by-environment interaction that is discussed on the background of previous studies relating the -703G/T polymorphism to anxiety, a personality dimension that has been shown to be a risk factor for nicotine dependence.

Sex, aggression and impulse control: an integrative account

There is evidence that the male sex and a personality style characterized by low self-control/high impulsivity and a propensity for negative emotionality increase the risk for impulsive aggressive, antisocial and criminal behavior. This article aims at identifying neurobiological factors underlying this association. It is concluded that the neurobiological correlates of impulsive aggression act through their effects on the ability to modulate impulsive expression more generally, and that sex-related differences in the neurobiological correlates of impulse control and emotion regulation mediate sex differences in direct aggression. A model is proposed that relates impulse control and its neurobiological correlates to sex differences in direct aggression.

The influence of hostility on electroencephalographic activity and memory functioning during an affective memory task

OBJECTIVE

The purpose of this study was to examine the neural correlates of emotional learning and hostility via the use of EEG and the Auditory Affective Verbal Learning Test (AAVL).

METHODS

The Cook-Medley Hostility Scale (CMHO) was used to identify right-handed men (N=16) and women (N=44) as low or high hostile. Participants were administered the positive and negative word lists of the AAVL lists, and were asked to recall the words during a 5-trial paradigm. EEG data were recorded from 19 scalp sites before and following learning trials; separate bandwidths of the EEG spectrum were analyzed.

RESULTS

As predicted, completion of the negative AAVL resulted in self-reported negative mood induction. Moreover, primacy and recency effects were demonstrated with the negative and positive versions of the AAVL, respectively. Unexpectedly, high hostiles demonstrated greater right versus left hemisphere high alpha power than low hostile counterparts. Low hostiles evidenced greater alpha power and low beta power than did high hostiles.

CONCLUSIONS

These results suggest differing patterns of hemispheric asymmetry and overall brain activity for low and high hostiles during emotional learning.

SIGNIFICANCE

The findings are important with regard to understanding the relationship between hostility, emotional learning, and associated neural systems.

Polymorphism of the 5-HT(2A) receptor gene: association with stress-related indices in healthy middle-aged adults

Past research has concentrated on the stress system and personality in order to explain the variance found in cognitive performance in old age. A growing body of research is starting to focus on genetic polymorphism as an individual difference factor to explain the observed heterogeneity in cognitive function. While the functional mechanism is still under investigation, polymorphism of the 5-HT(2A) receptor gene (-1438A/G) has been linked to certain behavioral and physiological outcomes, including cortisol secretion, the expression of certain personality traits, and memory performance. It was the goal of the present study to investigate the association between the -1438A/G polymorphism and stress hormone secretion, stress-related psychological measures, and cognitive performance in a group of adults between the ages of 50 and 65. To examine these associations, 101 middle-aged adults were recruited, completed a battery of psychological questionnaires and were administered a battery of cognitive tasks that assess frontal lobe and hippocampal function. Basal and stress-reactive salivary cortisol levels were collected, at home and in the laboratory. Analyses on psychological measures showed that participants with the GG genotype reported significantly higher levels of neuroticism compared to the AG group and higher levels of depression and more emotion-based coping strategies compared to both the AG and AA group. In terms of cortisol secretion, the AA genotype was related to a significantly higher awakening cortisol response (ACR) compared to the AG and GG group and the GG genotype group displayed a greater increase in cortisol secretion following a psychosocial stressor compared to the two other groups. On measures of cognitive performance, the AA genotype group performed significantly better on a test of declarative memory and selective attention compared to the other two groups. Together, these results suggest that carriers of the GG genotype are more susceptible to low mood and display a greater potential for an overactive stress system, which may influence cognitive function in later years.

Impaired executive control is associated with a variation in the promoter region of the tryptophan hydroxylase 2 gene

Current models of attention describe attention not as a homogenous entity but as a set of neural networks whose measurement yields a set of three endophenotypes-alerting, orienting, and executive control. Previous findings revealed different neuroanatomical regions for these subsystems, and data from twin studies indicate differences in their heritability. The present study investigated the molecular genetic basis of attention in a sample of 100 healthy subjects. Attention performance was assessed with the attention network test that distinguishes alerting, orienting, and executive control (conflict) using a simple reaction time paradigm with different cues and congruent and incongruent flankers. Two gene loci on candidate genes for cognitive functioning, the functional catechol-O-methyltransferase (COMT) VAL158MET and the tryptophan hydroxylase 2 (TPH2) -703 G/T promoter polymorphism, were tested for possible associations with attention. COMT is involved in the catabolism of dopamine, and TPH is the rate-limiting enzyme for serotonin synthesis. Results showed no effect of the COMT polymorphism on attention performance. However, the TT genotype of TPH2 -03 G/T was significantly associated with more errors (a possible indicator of impaired impulse control; p = .001) and with decreased performance in executive control (p = .001). This single-nucleotide polymorphism on the TPH2 gene explained more than 10% of the variance in both indicators of attention stressing the role of the serotonergic system for cognitive functions.