Dopamine Receptor Gene DRD4 7-Repeat Allele X Maternal Sensitivity Interaction on Child Externalizing Behavior Problems: Independent Replication of Effects at 18 Months

The impact of dopamine receptor D4, temperamental negativity, and household chaos on young twins' externalizing behaviors

Biological and genetic factors, as well as contextual influences, contribute to the etiology of externalizing behaviors in children and adolescents. The current project used a longitudinal design to examine how individual vulnerability for externalizing behavior is influenced by the interplay among biological/genetic and environmental factors, and how this occurs across development. We investigated the influence of dopamine receptor D4 genotype (DRD4), child temperament, and household chaos on children's externalizing behaviors using a sample of twins/triplets tested at the ages of 4 and 5 years (n = 229), including a subset of these who were tested again in middle childhood (ages 7-13 years; n = 174). Multilevel linear regression modeling demonstrated that the DRD4-7repeat genotype, 4-year-old negative affectivity, and household chaos at the age of 4 years were related to 5-year-old externalizing behaviors. Stability in externalizing behaviors from the age of 5 years to middle childhood was demonstrated. A significant interaction between DRD4 and household chaos showed that children with no 7-repeat DRD4 alleles had significantly higher levels of externalizing in homes with extremely low levels of parent-reported chaos, suggesting a "goodness-of-fit" pattern of gene-environment interaction. These findings suggest that risk for childhood externalizing behaviors is likely multifaceted and differs across developmental periods.

The effect of the 7R allele at the DRD4 locus on risk tolerance is independent of background risk in Senegalese fishermen

It has been shown that living in risky environments, as well as having a risky occupation, can moderate risk-tolerance. Despite the involvement of dopamine in the expectation of reward described by neurobiologists, a GWAS study was not able to demonstrate a genetic contribution of genes involved in the dopaminergic pathway in risk attitudes and gene candidate studies gave contrasting results. We test the possibility that a genetic effect of the DRD4-7R allele in risk-taking behavior could be modulated by environmental factors. We show that the increase in risk-tolerance due to the 7R allele is independent of the environmental risk in two populations in Northern Senegal, one of which is exposed to a very high risk due to dangerous fishing.

ADHD co-morbidities: A review of implication of gene × environment effects with dopamine-related genes

ADHD is a major burden in adulthood, where co-morbid conditions such as depression, substance use disorder and obesity often dominate the clinical picture. ADHD has substantial shared heritability with other mental disorders, contributing to comorbidity. However, environmental risk factors exist but their interaction with genetic makeup, especially in relation to comorbid disorders, remains elusive. This review for the first time summarizes present knowledge on gene x environment (GxE) interactions regarding the dopamine system. Hitherto, mainly candidate (GxE) studies were performed, focusing on the genes DRD4, DAT1 and MAOA. Some evidence suggest that the variable number tandem repeats in DRD4 and MAOA may mediate GxE interactions in ADHD generally, and comorbid conditions specifically. Nevertheless, even for these genes, common variants are bound to suggest risk only in the context of gender and specific environments. For other polymorphisms, evidence is contradictory and less convincing. Particularly lacking are longitudinal studies testing the interaction of well-defined environmental with polygenic risk scores reflecting the dopamine system in its entirety.

Longitudinal Influences of DRD4 Polymorphism and Early Maternal Caregiving on Personality Development and Problem Behavior in Middle Childhood and Adolescence

Most studies examining gene-environment effects on self-regulation focus on outcomes early childhood or adulthood. However, only a few studies investigate longitudinal effects during middle childhood and adolescence and compare two domains of early caregiving. In a longitudinal follow-up with a sample of N = 87, we studied the effects of differences in the DRD4 tandem repeat polymorphisms and two domains of early maternal caregiving quality on children's personality development using Block's California Child Q-Set (CCQ) at age six and age 12 and on problem behavior at ages six and seven. Early maternal regulation quality predicted later ego-resiliency and aggressiveness. In addition, significant gene-environment interactions revealed that children with the 7+ DRD4 tandem repeat polymorphism and poor maternal regulation quality in infancy showed lower scores in ego-resiliency and higher scores in ego-undercontrol and CCQ aggressiveness. In contrast, children who had experienced effective maternal regulation in infancy showed a comparable level in personality traits and problem behavior as the DRD4 7- group independent of the levels of maternal regulatory behavior. Similarly, longitudinal caregiving × DRD4 interactions were found for behavior problems in middle childhood, especially for oppositional-aggression, inattentive-hyperactivity, and social competence. Early caregiving effects were only found for maternal regulation quality, but not for maternal responsiveness. Effective early maternal regulation in infancy can moderate the negative effect of DRD4 7+ on children's self-regulation in middle childhood and adolescence. However, maternal responsiveness has no comparable effects. It seems relevant to consider several dimensions of early caregiving and to also measure the environment in more detail in gene-environment studies.

The gray matter volume of the temporoparietal junction varies across cultures: a moderating role of the dopamine D4 receptor gene (DRD4)

Prior work shows that compared to European Americans, East Asians show an enhanced propensity to take the perspective of another person. In the current work, we tested whether this cultural difference might be reflected in the gray matter (GM) volume of the temporoparietal junction (TPJ), a brain region selectively implicated in perspective taking and mentalizing. We also explored whether the cultural difference in the TPJ GM volume might be moderated by dopamine D4 receptor gene (DRD4) exon 3 variable-number tandem repeat polymorphism. Structural magnetic resonance imaging of 66 European Americans and 66 East Asian-born Asians were subjected to voxel-based morphometry. It was observed that the GM volume of the right TPJ was greater among East Asians than among European Americans. Moreover, this cultural difference was significantly more pronounced among carriers of the 7- or 2-repeat allele of DRD4 than among the non-carriers of these alleles. Our findings contribute to the growing evidence that culture can shape the brain.

The roles of comorbidity and trauma exposure and its timing in shaping HPA axis patterns in depression

BACKGROUND

Much work has documented hypothalamic pituitary adrenal (HPA) axis abnormalities in major depressive disorder (MDD), but inconsistencies leave this system's role in the illness unclear. Comparisons across studies are complicated by variation in co-morbidity (Posttraumatic Stress Disorder-PTSD, anxiety disorders), exposure to trauma, and timing of trauma (child vs. adult). Here, we examined the impact of these factors on HPA axis profiles in depression.

METHODS

We recruited 5 groups of participants: MDD (n = 14), comorbid MDD + PTSD following adulthood trauma (MDD + PTSD-Adult; n = 12), comorbid MDD + PTSD following childhood trauma (MDD + PTSD-Child; n = 18), comorbid MDD + social anxiety disorder (MDD + SAD; n = 12), and non-depressed control participants who were sex and age matched to patients (combined total n = 36). HPA axis function was assessed using three challenges: stress reactivity via the Trier Social Stress Test (TSST), feedback sensitivity via a dexamethasone suppression test (DST), and central drive via a metyrapone challenge (MET). We compared hormonal responses between patient groups and their respective non-depressed controls.

RESULTS

MDD + PTSD-Child showed low cortisol levels at baseline, and reduced adrenocorticotropic hormone (ACTH) levels at baseline and throughout the TSST. MDD-only, MDD + PTSD-Adult, and MDD + SAD did not differ from non-depressed controls in HPA axis responses to the TSST. Controlling for childhood trauma severity, the reduced baseline levels in MDD + PTSD-Child were no longer significant and significantly reduced baseline cortisol levels emerged for MDD + PTSD-Adult. No diagnostic group effects were detected with DST and MET. Childhood maltreatment subtypes were associated with unique HPA axis responses to TSST and MET.

CONCLUSION

Comorbidity and trauma exposure, as well as their timing and type, contribute to inconsistencies in the depression literature and must be included in efforts to clarify the role of the HPA axis in MDD.

Gene set enrichment analysis to create polygenic scores: a developmental examination of aggression

Previous approaches for creating polygenic risk scores (PRSs) do not explicitly consider the biological or developmental relevance of the genetic variants selected for inclusion. We applied gene set enrichment analysis to meta-GWAS data to create developmentally targeted, functionally informed PRSs. Using two developmentally matched meta-GWAS discovery samples, separate PRSs were formed, then examined in time-varying effect models of aggression in a second, longitudinal sample of children (n = 515, 49% female) in early childhood (2-5 years old), and middle childhood (7.5-10.5 years old). Functional PRSs were associated with aggression in both the early and middle childhood models.

Cultural variation in the gray matter volume of the prefrontal cortex is moderated by the dopamine D4 receptor gene (DRD4)

Recent evidence suggests a systematic cultural difference in the volume/thickness of prefrontal regions of the brain. However, origins of this difference remain unclear. Here, we addressed this gap by adopting a unique genetic approach. People who carry the 7- or 2-repeat (7/2-R) allele of the dopamine D4 receptor gene (DRD4) are more sensitive to environmental influences, including cultural influences. Therefore, if the difference in brain structure is due to cultural influences, it should be moderated by DRD4. We recruited 132 young adults (both European Americans and Asian-born East Asians). Voxel-based morphometry showed that gray matter (GM) volume of the medial prefrontal cortex and the orbitofrontal cortex was significantly greater among European Americans than among East Asians. Moreover, the difference in GM volume was significantly more pronounced among carriers of the 7/2-R allele of DRD4 than among non-carriers. This pattern was robust in an alternative measure assessing cortical thickness. A further exploratory analysis showed that among East Asian carriers, the number of years spent in the U.S. predicted increased GM volume in the orbitofrontal cortex. The present evidence is consistent with a view that culture shapes the brain by mobilizing epigenetic pathways that are gradually established through socialization and enculturation.

Oppositional defiant disorder: current insight

Oppositional defiant disorder (ODD) is diagnosed broadly on the basis of frequent and persistent angry or irritable mood, argumentativeness/defiance, and vindictiveness. Since its inception in the third Diagnostic and Statistical Manual of Mental Disorders, epidemiological and longitudinal studies have strongly suggested a distinct existence of ODD that is different from other closely related externalizing disorders, with different course and outcome and possibly discrete subtypes. However, several issues, such as symptom threshold, dimensional versus categorical conceptualization, and sex-specific symptoms, are yet to be addressed. Although ODD was found to be highly heritable, no genetic polymorphism has been identified with confidence. There has been a definite genetic overlap with other externalizing disorders. Studies have begun to explore its epigenetics and gene–environment interaction. Neuroimaging findings converge to implicate various parts of the prefrontal cortex, amygdala, and insula. Alteration in cortisol levels has also been demonstrated consistently. Although a range of environmental factors, both familial and extrafamilial, have been studied in the past, current research has combined these with other biological parameters. Psychosocial treatment continues to be time-tested and effective. These include parental management training, school-based training, functional family therapy/brief strategic family therapy, and cognitive behavior therapy. Management of severe aggression and treatment of co-morbid disorders are indications for pharmacotherapy. In line with previous conceptualization of chronic irritability as a bipolar spectrum abnormality, most studies have explored antipsychotics and mood stabilizers in the management of aggression, with limited effects.

Affective Teacher-Student Relationships and Students' Externalizing Behavior Problems: A Meta-Analysis

This meta-analysis of 57 primary studies with 73,933 students shows strong links between affective teacher-student relationships (TSRs) and students' externalizing behavior problems (EBPs). Moreover, students' culture, age, gender, and the report types of EBPs moderated these effects. The negative correlation between positive indicators of affective TSRs and students' EBPs was stronger (a) among Western students than Eastern ones, (b) for students in the lower grades of primary school than for other students, (c) when rated by teachers or parents than by students or peers, and (d) among females than among males. In contrast, the positive correlation between negative indicators of affective TSRs and students' EBPs was stronger (a) among Eastern students than Western ones, (b) for students in the higher grades of primary school than for other students, and