Differential susceptibility in a developmental perspective: DRD4 and maternal sensitivity predicting externalizing behavior

Developmental cascades from early childhood attachment security to adolescent level of personality functioning among high-risk youth

This study examines associations between early childhood attachment security and adolescent personality functioning in a high-risk sample within a developmental psychopathology framework. Data from 2,268 children (1165 male; 1103 female) and caregivers participating in Future of Families and Child Well-Being Study (FFCWS) were used to examine (1) effects of genetic polymorphisms of the serotonin transporter (5-HTTLPR) and dopamine D4 receptor (DRD4) genes and adverse childhood experiences (ACEs) on attachment security and emotional and behavioral dysregulation in early childhood and (2) longitudinal associations and transactional relationships among attachment security, dysregulation, negative parenting attitudes and behaviors, social competence, and adolescent personality functioning. Results revealed that ACEs predicted attachment security over and above sex or the genetic risk, and gene × environment interactions did not increment prediction. Results of cascade models showed that greater early childhood attachment security predicted higher adolescent level of personality functioning via pathways through intermediary variables. Limitations and future research directions are discussed.

Associations of Duration of Preadoption Out-of-home Care, Genetic Risk for Schizophrenia Spectrum Disorders and Adoptive Family Functioning with Later Psychiatric Disorders of Adoptees

The objective was to examine the impacts of duration of preadoption out-of-home care and adoptive family functioning on later psychiatric morbidity of adoptees with high (HR) and low (LR) genetic risk for schizophrenia spectrum disorders. The study uses nationwide data from the Finnish Adoptive Family Study of Schizophrenia. The study population in this substudy consisted of 43 h adoptees and 128 LR adoptees. Of these adoptees, 90 had spent 0-6 months and 81 over 6 months in preadoption out-of-home care. The family functioning of adoptive families was assessed based on Global Family Ratings and psychiatric disorders on DSM-III-R criteria. The results showed that among the adoptees with over 6 months in preadoption out-of-home care, the likelihood for psychiatric disorders was significantly increased in HR adoptees compared to LR adoptees. In adoptees with 6 months or less in preadoption out-of-home care, an increased likelihood for psychiatric disorders was found among those living in adoptive families with dysfunctional processes. These findings indicate that especially for HR children, a well-functioning early caregiving environment is crucial in terms of subsequent mental wellbeing. The results emphasize that when adoption is necessary, early placement and well-functioning adoptive family environment are beneficial to children.

Annual Research Review: Prenatal opioid exposure - a two-generation approach to conceptualizing neurodevelopmental outcomes

Opioid use during pregnancy impacts the health and well-being of two generations: the pregnant person and the child. The factors that increase risk for opioid use in the adult, as well as those that perpetuate risk for the caregiver and child, oftentimes replicate across generations and may be more likely to affect child neurodevelopment than the opioid exposure itself. In this article, we review the prenatal opioid exposure literature with the perspective that this is not a singular event but an intergenerational cascade of events. We highlight several mechanisms of transmission across generations: biological factors, including genetics and epigenetics and the gut-brain axis; parent-child mechanisms, such as prepregnancy experience of child maltreatment, quality of parenting, infant behaviors, neonatal opioid withdrawal diagnosis, and broader environmental contributors including poverty, violence exposure, stigma, and Child Protective Services involvement. We conclude by describing ways in which intergenerational transmission can be disrupted by early intervention.

Conduct Problems and Hair Cortisol Concentrations Decrease in School-Aged Children after VIPP-SD: A Randomized Controlled Trial in Two Twin Cohorts

The Video-feedback Intervention to promote Positive Parenting and Sensitive Discipline (VIPP-SD) is effective in increasing parental sensitivity and sensitive discipline, and aims to decrease child behavior problems. Changes in quality of parenting may be accompanied by effects on child stress levels. However, studies of VIPP-SD effects on child behavior problems have shown mixed results and there are no studies to date of the effect of the intervention on children's stress levels, as measured by hair cortisol concentration (HCC). Furthermore, differences in intervention effectiveness may be explained by differential susceptibility factors. We hypothesized that the effects of the VIPP-SD on child behavior problems might be moderated by currently available child polygenic scores of differential susceptibility (PGS-DS). In the current pre-registered trial, we randomly assigned 40% of n = 445 families with school-aged twin children to the intervention group. The VIPP-SD was successful in decreasing both children's conduct problems and HCC. Effects were not moderated by available child PGS-DS. We conclude that a brief, home-based video-feedback parenting intervention can decrease child behavior problems and affect the child's stress-related neuroendocrine system as assessed with hair cortisol. In future studies, more specific PGS-DS for externalizing behaviors should be used as well as parental PGS-DS.

Individual differences in sensitivity to positive home environment among children "at risk" for attention-deficit/hyperactivity disorder: A review

Although the evidence for the genetic basis of attention-deficit/hyperactivity disorder (ADHD) is strong, environmental factors, such as the quality of parenting or the home environment, may moderate such genetic liability. The plausible negative effect of a low-quality home environment and negative parenting on child outcomes is well-established; however, the positive effect of a high-quality environment and positive parenting remained largely uninvestigated. Due to the presence of genetic, temperamental, or physiological factors, children who were traditionally considered at-risk for ADHD may be more sensitive to aspects of their environment compared to children who are not at such risk. Therefore, they would be more affected by their environmental experience, either for good or bad. Under supportive environmental conditions, such at-risk individuals might actually outperform their non-vulnerable peers, suggesting that these individual factors might be considered susceptibility factors rather than risk factors. Little is known regarding the positive effect of the environment in the ADHD literature, but it has been demonstrated in cognitive functions that are closely associated with ADHD, such as executive functions (EF). We review this literature and examine the extant empirical support for sensitivity to aspects of the home environment and parenting in the case of ADHD and EF. Moreover, we review factors that could help identify the specific aspects of the home environment and parenting that these children might be more susceptible to. Such knowledge could be valuable when designing preventive interventions and identifying those children that are especially sensitive and could benefit from such interventions. Recommendations for future studies are discussed as well.

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.

Parental sensitivity and child behavioral problems: A meta-analytic review

Meta-analytic associations between observed parental sensitivity and child behavioral problems were examined (children aged 0-17 years). Studies (k = 108, N = 28,114) contained sociodemographically diverse samples, primarily from North America and Europe, reporting on parent-child dyads (95% mothers; 54% boys). Sensitivity significantly related to internalizing (k = 69 studies; N = 14,729; r = -.08, 95% CI [-.12, -.05]) and externalizing (k = 94; N = 25,418; r = -.14, 95% CI [-.17, -.11]) problems, with stronger associations found for externalizing. For internalizing problems, associations were significantly stronger among samples with low socioeconomic status (SES) versus mid-high SES, in peer-reviewed versus unpublished dissertations, and in studies using composite versus single scale sensitivity measures. No other moderators emerged as significant.

Understanding trajectories of externalizing problems: Stability and emergence of risk factors from infancy to middle adolescence

Despite considerable efforts to understand the processes that underlie the development of externalizing behavior problems, it is still unclear why externalizing problems remain chronically high for some children, emerge early and cease by late childhood for others, and arise in adolescence in some cases. The purpose of this study was to examine how a wide range of child and family risk factors are linked to trajectories of externalizing behavior and how these relationships vary from infancy to middle adolescence. We used data from the community-based Norwegian Tracking Opportunities and Problems (TOPP) study sample (n = 921). A Cholesky factorization model was specified to separate stable and emerging risk doses across four developmental periods (infancy, early and middle childhood, and middle adolescence). Children in the High Stable class were characterized by substantially elevated risk levels in multiple domains throughout the study period. Children in the High Childhood Limited class had very high levels of temperamental emotionality, internalizing symptoms, and maternal mental distress, suggesting a substantial intrinsic emotional basis for their externalizing problems. Intrinsic factors seemed less salient for the Adolescent Onset class. These findings emphasize the need for a dynamic perspective on risk factors and support the importance of prevention and intervention efforts across multiple domains from early childhood and throughout adolescence.

Neural and behavioral signatures of social evaluation and adaptation in childhood and adolescence: The Leiden consortium on individual development (L-CID)

The transition period between early childhood and late adolescence is characterized by pronounced changes in social competence, or the capacity for flexible social adaptation. Here, we propose that two processes, self-control and prosociality, are crucial for social adaptation following social evaluation. We present a neurobehavioral model showing commonalities in neural responses to experiences of social acceptance and rejection, and multiple pathways for responding to social context. The Leiden Consortium on Individual Development (L-CID) provides a comprehensive approach towards understanding the longitudinal developmental pathways of, and social enrichment effects on, social competence, taking into account potential differential effects of such enrichment. Using Neurosynth based brain maps we point towards the medial prefrontal cortex as an important region integrating social cognition, self-referential processing and self-control for learning to respond flexibly to changing social contexts. Based on their role in social evaluation processing, we suggest to examine medial prefrontal cortex connections with lateral prefrontal cortex and the ventral striatum as potential neural differential susceptibility markers, in addition to previously established markers of differential susceptibility.

Socioemotional Mechanisms of Children's Differential Response to the Effects of Maternal Sensitivity on Child Adjustment

OBJECTIVE

Children differ in the extent to which they reap the benefits of maternal sensitive care or suffer the adverse consequences of insensitive care, and these differences can be accounted for by biological characteristics. However, how susceptible children adapt to maternal sensitivity in ways that either maximize positive development or lead to maladjustment has yet to be determined. Here, we propose a novel model of socioemotional mechanisms by which the joint influences of maternal sensitivity and child biological characteristics influence child adjustment.

DESIGN

We propose a theoretical model, in which children's vagal functioning and polymorphisms in serotonin transporter (5-HTTLPR) and dopamine receptor D4 (DRD4) genes confer susceptibility to the effects of maternal sensitivity on internalizing, externalizing, prosocial and moral behavior via changes in interpersonal strategies for emotion regulation, the threat response system, and empathy.

RESULTS

Theoretical and empirical support for the proposed mechanisms are provided.

CONCLUSIONS

The proposed mechanistic model of susceptibility to maternal sensitivity offers a novel framework of for whom and how children are affected by early maternal care, highlighting multiple reciprocal, interacting influences across genes, physiology, behavior, and the environment.

The relevance of a rodent cohort in the Consortium on Individual Development

One of the features of the Consortium on Individual Development is the existence of a rodent cohort, in parallel with the human cohorts. Here we give an overview of the current status. We first elaborate on the choice of rat and mouse models mimicking early life adverse or beneficial conditions during development. We performed a systematic literature search on early life adversity and adult social behavior to address the status quo. Next, we describe the behavioral tasks we used and designed to examine behavioral control and social competence in rodents. The results so far indicate that manipulation of the environment in the first postnatal week only subtly affects social behavior. Stronger effects were seen in the model that targeted early adolescence; once adult, these rats are characterized by increased attention, a higher degree of impulsiveness and reduced social interest in peers. Many experiments in our rodent models with tightly controlled conditions were inspired by findings in human cohorts, and now allow in-depth mechanistic investigations. Vice versa, some of the findings in rodents are currently followed up by dedicated investigations in the human cohorts. This exemplifies the added value of animal investigations in a consortium encompassing primarily human developmental cohorts.

How Heritable are Parental Sensitivity and Limit-Setting? A Longitudinal Child-Based Twin Study on Observed Parenting

We examined the relative contribution of genetic, shared environmental and non-shared environmental factors to the covariance between parental sensitivity and limit-setting observed twice in a longitudinal study using a child-based twin design. Parental sensitivity and parental limit-setting were observed in 236 parents with each of their same-sex toddler twin children (M_age  = 3.8 years; 58% monozygotic). Bivariate behavioral genetic models indicated substantial effects of similar shared environmental factors on parental sensitivity and limit-setting and on the overlap within sensitivity and limit-setting across 1 year. Moderate child-driven genetic effects were found for parental limit-setting in year 1 and across 1 year. Genetic child factors contributing to explaining the variance in limit-setting over time were the same, whereas shared environmental factors showed some overlap.

Using the Actor-Partner Interdependence Model to assess maternal and infant contributions to mother-infant affective exchanges during the Still-Face Paradigm

This study describes maternal and infant contributions to dyadic affective exchanges during the Still-Face Paradigm (SFP) in an understudied mostly low-income sample. One hundred eleven mothers and their 7-month-old infants were videotaped during the SFP to analyze how a social stressor affects mother-infant positive and negative affective exchanges during interaction. The SFP includes 3 episodes: baseline, maternal still-face, and reunion. Maternal and infant positive and negative affect were scored by masked reliable coders. Data were analyzed using the Actor-Partner Interdependence Model to test the hypotheses that each partner's affectivity during the baseline episode would predict their own affectivity during the reunion episode (actor effects). We also expected that each partner's affectivity during the baseline episode would influence the other partner's affectivity during the reunion episodes (partner effects). After controlling for infant sex and maternal education, results provided evidence for actor effects for maternal and infant positive affect, and for partner effects for maternal baseline positive affect to infant positive affect during the reunion. One significant partner effect was observed for negative affect: Infant negativity during baseline predicted greater maternal negativity during reunion. Findings confirm that both mothers and infants contribute to dyadic affective processes during the SFP but specific findings vary depending on the affective valence in question. Clinical implications and future research are discussed.

The effects of different rearing conditions on sexual maturation and maternal care in heterozygous mineralocorticoid receptor knockout mice

Sexual and social development is affected by a complex interplay between genetic makeup and the early-life rearing environment. While many rodent studies focused primarily on the detrimental effects of early-life stress, human literature suggests that genetic susceptibility may not be restricted to negative environments; it may also enhance the beneficial effects of positive rearing conditions. To examine this interaction in a controlled setting, heterozygous mineralocorticoid receptor knockout (MR^+/-) mice and control litter mates were exposed to a limited nesting/bedding (LN, impoverished), standard nesting (SN, control) or communal nesting (CN, enriched) paradigm from postnatal day 2-9 (P2-P9). Offspring was monitored for puberty onset between P24-P36 and, in females, maternal care-giving (i.e. as F1) during adulthood, after which basal corticosterone was measured. Different home-cage environments resulted in profound differences in received maternal care and offspring body weight. In male offspring, LN resulted in delayed puberty onset that was mediated by body weight and unpredictability of maternal care received during early development. In female offspring, rearing condition did not significantly alter sexual maturation and had little effect on their own maternal care-giving behavior. Genotype did affect maternal care: female MR^+/- offspring exhibited a less active nursing style and upregulated fragmentation during adulthood, irrespective of early life conditions. Basal corticosterone levels were highest in MR^+/- mice with a background of LN. Overall, we found a gene-by-environment interaction with respect to basal corticosterone levels, but not for sexual maturation or maternal behavior.

Frühkindliche Prädiktoren externalisierender Verhaltensauffälligkeiten

Zusammenfassung. Externalisierende Verhaltensauffälligkeiten sind mit hohen gesellschaftlichen Kosten verbunden. Damit wirksame Präventions- und frühe Therapieprogramme entwickelt werden können, ist es notwendig, bereits in den ersten Lebensjahren Risiken für einen externalisierenden Entwicklungsverlauf zu identifizieren. In einer systematischen Literaturrecherche konnten aus 21 Publikationen zu 12 längsschnittlichen Geburtskohorten mit insgesamt 55 077 Kindern frühe Risiken bezogen auf eine elterliche Psychopathologie, einen niedrigen sozio-ökonomischen Status und ungünstige Eltern-Kind-Interaktionen identifiziert werden. Insbesondere eine mütterliche Depression, ein niedriger sozio-ökonomischer Status und ein harsches Erziehungsverhalten in den ersten Lebensjahren waren prädiktiv für externalisierende Verhaltensauffälligkeiten im Kindergarten und bei Schuleintritt. Implikationen für die klinische Praxis werden vorgestellt.

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.

Mothers' Personal and Interpersonal Function as Potential Mediators Between Maternal Maltreatment History and Child Behavior Problems

This study examined maternal depressive symptoms, social support, parenting, and adult attachment as mediators explaining the relation between maternal childhood maltreatment and child behavior in offspring. We assessed a community sample of 96 mother-child dyads. At child age 16 months, mothers self-reported maltreatment history, adult attachment, depressive symptoms, and social support, and maternal sensitivity was assessed via 2 hr of direct behavioral observation. Maternal reports of child behavior were collected at 5 years. Single and parallel mediation models were constructed. Only maternal depressive symptoms mediated the relation between maternal maltreatment history and children's internalizing problems. Maternal sensitivity emerged as a suppressor variable. With respect to the relation between maternal maltreatment history and children's externalizing problems, when entered singly, maternal depressive symptoms, social support, and avoidant attachment emerged as mediators. When examined in parallel, only maternal depressive symptoms and avoidant attachment accounted for unique mediating variance. Findings have implications with respect to important maternal factors that might be targeted to reduce the probability of maladaptive child behavior.

How evolutionary thinking can help us to understand ADHD

We argue that current debates about attention-deficit hyperactivity disorder (ADHD) can be considered afresh using an evolutionary lens. We show how the symptoms of ADHD can often be considered adaptive to their specific environment. We suggest that, from an evolutionary point of view, ADHD symptoms might be understood to result from an ‘evolutionary mismatch’, in which current environmental demands do not fit with what evolution has prepared us to cope with. For example, in our ancestral environment of evolutionary adaptedness (EEA), children were not expected to sit still and concentrate on academic tasks for many hours a day. Understanding ADHD in terms of such a ‘mismatch’ raises significant issues regarding the management of childhood ADHD, including ethical ones. An approach based on the concept of mismatch could provide an alternative to current debates on whether ADHD results from nature or nurture and whether it is under- or over-diagnosed. It would allow clinicians and policy makers to take both the child and the environment into account and consider what might be desirable and feasible, both in society and for specific children, to lessen the mismatch.

LEARNING OBJECTIVES

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Chronic Stressors and Adolescents' Externalizing Problems: Genetic Moderation by Dopamine Receptor D4. The TRAILS Study

The existing literature does not provide consistent evidence that carriers of the Dopamine D4 Receptor 7-repeat allele are more sensitive to adverse environmental influences, resulting in enhanced externalizing problems, compared to noncarriers. One explanation is that the adverse influences examined in prior studies were not severe, chronic, or distressing enough to reveal individual differences in sensitivity reflected by DRD4–7R. This study examined whether the 7-repeat allele moderated the association between chronic stressors capturing multiple stressful aspects of individuals’ lives and externalizing problems in adolescence. We expected that chronic stressor levels would be associated with externalizing levels only in 7-repeat carriers. Using Linear Mixed Models, we analyzed data from 1621 Dutch adolescents (52.2% boys), obtained in three measurement waves (mean age approximately 11, 13.5, and 16 years) from the TRacking Adolescents’ Individual Lives Survey (TRAILS) population-based birth cohort and the parallel clinic-referred cohort. Across informants, we found that higher levels of chronic stressors were related to higher externalizing levels in 7-repeat carriers but not in noncarriers, as hypothesized. Although previous studies on the 7-repeat allele as a moderator of environmental influences on adolescents’ externalizing problems have not convincingly demonstrated individual differences in sensitivity to adverse environmental influences, our findings suggest that adolescent carriers of the Dopamine D4 Receptor 7-repeat allele are more sensitive to chronic, multi-context stressors than noncarriers.

A DRD4 gene by maternal sensitivity interaction predicts risk for overweight or obesity in two independent cohorts of preschool children

BACKGROUND

Recent evidence suggests that early exposure to low maternal sensitivity is a risk factor for obesity in children and adolescents. A separate line of study shows that the seven-repeat (7R) allele of the dopamine-4 receptor gene (DRD4) increases susceptibility to environmental factors including maternal sensitivity. The current study integrates these lines of work by examining whether preschoolers carrying the 7R allele are more vulnerable to low maternal sensitivity as it relates to overweight/obesity risk.

METHOD

The Maternal Adversity Vulnerability and Neurodevelopment (MAVAN) project in Canada was used as the discovery cohort (N = 203), while the Generation R study in the Netherlands was used as a replication sample (N = 270). Regression models to predict both continuous BMI z-scores and membership in any higher BMI category based on established World Health Organization (WHO) cutoffs for 48 months of age were completed.

RESULTS

In both cohorts, there was a significant maternal sensitivity by DRD4 by sex interaction predicting higher body mass indices and/or obesity risk. As hypothesized, post hoc testing revealed an inverse relationship between maternal sensitivity and body mass indices in 7R allele carriers relative to noncarriers. This finding was strongest in girls in the Canadian cohort and in boys in the Dutch cohort.

CONCLUSIONS

Many children who carry the 7R allele of DRD4 appear to be more influenced by maternal sensitivity as it relates to overweight/obesity risk, consistent with a plasticity effect. Given the relatively small sample sizes available for these analyses, further replications will be needed to confirm and extend these results.

Children's differential susceptibility to parenting: An experimental test of "for better and for worse"

Differential susceptibility theory proposes that a subset of individuals exist who display enhanced susceptibility to both negative (risk-promoting) and positive (development-enhancing) environments. This experiment represents the first attempt to directly test this assumption by exposing children in the experimental group to both negative and positive feedback using puppet role-plays. It thereby serves as an empirical test as well as a methodological primer for testing differential susceptibility. Dutch children (N=190, 45.3% girls) between the ages of 4 and 6years participated. We examined whether negative and positive feedback would differentially affect changes in positive and negative affect, in prosocial and antisocial intentions and behavior, depending on children's negative emotionality. Results show that on hearing negative feedback, children in the experimental group increased in negative affect and decreased in positive affect more strongly than children in the control group. On hearing positive feedback, children in the experimental group tended to increase in positive affect and decrease in prosocial behavior. However, changes in response to negative or positive feedback did not depend on children's negative emotionality. Moreover, using reliable change scores, we found support for a subset of "vulnerable" children but not for a subset of "susceptible" children. The findings offer suggestions to guide future differential susceptibility experiments.

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

The DRD4 VNTR has been associated with child behavior problems in interaction with maternal insensitivity in European and American cohorts of preschoolers, with the 7-repeat (7R) allele associated with greater problems. We sought to replicate and expand these findings by examining effects on reports of child behavior problems at 18 months. A 63 family sample with data for observed maternal sensitivity ratings, DRD4 VNTR genotype, and maternal report of child behavior problems at 18-months was used in this preliminary analysis. Maternal sensitivity was measured at 6-months of age using laboratory observational measures (free-play and a teaching task). Maternal report of toddler behavior was obtained at 18-months via the standard Child Behavior Checklist, and infant genotype on the DRD4 VNTR was obtained using PCR. Infants carrying the DRD4 7R allele showed greater effects of maternal insensitivity than non-carriers for behavioral problems at 18-months. We replicated previous findings of association of infant DRD4 x maternal sensitivity interactions with child Externalizing problems in the European-ancestry sample (N = 42) in a median split of maternal sensitivity (p = .00011, eta2 = .329) and in regression analyses controlling for maternal age, maternal depression, and child gender in European ancestry (B = -3.4, SE 1.33, p = .01) and the total sample (B = -2.2, SE 1.02, p = .02). Exploratory analyses also found evidence of DRD4 x maternal sensitivity interaction with the CBCL ADHD scale. These findings replicate in an independent cohort DRD4 x maternal insensitivity interaction effect on child externalizing behavior problems at 18 months, further supporting the role of the DRD4 genotype in differential sensitivity to parenting.

Beyond main effects of gene-sets: harsh parenting moderates the association between a dopamine gene-set and child externalizing behavior

BACKGROUND

In a longitudinal cohort study, we investigated the interplay of harsh parenting and genetic variation across a set of functionally related dopamine genes, in association with children's externalizing behavior. This is one of the first studies to employ gene-based and gene-set approaches in tests of Gene by Environment (G × E) effects on complex behavior. This approach can offer an important alternative or complement to candidate gene and genome-wide environmental interaction (GWEI) studies in the search for genetic variation underlying individual differences in behavior.

METHODS

Genetic variants in 12 autosomal dopaminergic genes were available in an ethnically homogenous part of a population-based cohort. Harsh parenting was assessed with maternal (n = 1881) and paternal (n = 1710) reports at age 3. Externalizing behavior was assessed with the Child Behavior Checklist (CBCL) at age 5 (71 ± 3.7 months). We conducted gene-set analyses of the association between variation in dopaminergic genes and externalizing behavior, stratified for harsh parenting.

RESULTS

The association was statistically significant or approached significance for children without harsh parenting experiences, but was absent in the group with harsh parenting. Similarly, significant associations between single genes and externalizing behavior were only found in the group without harsh parenting. Effect sizes in the groups with and without harsh parenting did not differ significantly. Gene-environment interaction tests were conducted for individual genetic variants, resulting in two significant interaction effects (rs1497023 and rs4922132) after correction for multiple testing.

CONCLUSION

Our findings are suggestive of G × E interplay, with associations between dopamine genes and externalizing behavior present in children without harsh parenting, but not in children with harsh parenting experiences. Harsh parenting may overrule the role of genetic factors in externalizing behavior. Gene-based and gene-set analyses offer promising new alternatives to analyses focusing on single candidate polymorphisms when examining the interplay between genetic and environmental factors.

Genetic predispositions and parental bonding interact to shape adults' physiological responses to social distress

Parental bonding and oxytocin receptor (OXTR) gene genotype each influences social abilities in adulthood. Here, we hypothesized an interaction between the two - environmental experience (parental bonding history) and genetic factors (OXTR gene genotype) - in shaping adults' social sensitivity (physiological response to distress). We assessed heart rate and peripheral temperature (tip of the nose) in 42 male adults during presentation of distress vocalizations (distress cries belonging to female human infants and adults as well as bonobo). The two physiological responses index, respectively, state of arousal and readiness to action. Participants' parental bonding in childhood was assessed through the self-report Parental Bonding Instrument. To assess participants' genetic predispositions, buccal mucosa cell samples were collected, and region rs2254298 of the oxytocin receptor gene was analyzed: previous OXTR gene findings point to associations between the G allele and better sociality (protective factor) and the A allele and poorer sociality (risk factor). We found a gene * environment interaction for susceptibility to social distress: Participants with a genetic risk factor (A carriers) with a history of high paternal overprotection showed higher heart rate increase than those without this risk factor (G/G genotype) to social distress.Also, a significant effect of the interaction between paternal care and genotype on nose temperature changes was found. This susceptibility appears to represent an indirect pathway through which genes and experiences interact to shape mature social sensitivity in males.

Differential Susceptibility of the Developing Brain to Contextual Adversity and Stress

A swiftly growing volume of literature, comprising both human and animal studies and employing both observational and experimental designs, has documented striking individual differences in neurobiological sensitivities to environmental circumstances within subgroups of study samples. This differential susceptibility to social and physical environments operates bidirectionally, in both adverse and beneficial contexts, and results in a minority subpopulation with remarkably poor or unusually positive trajectories of health and development, contingent upon the character of environmental conditions. Differences in contextual susceptibility appear to emerge in early development, as the interactive and adaptive product of genetic and environmental attributes. This paper surveys what is currently known of the mechanisms or mediators of differential susceptibility, at the levels of temperament and behavior, physiological systems, brain circuitry and neuronal function, and genetic and epigenetic variation. It concludes with the assertion that differential susceptibility is inherently grounded within processes of biological moderation, the complexities of which are at present only partially understood.

Underlying Mechanisms of Gene-Environment Interactions in Externalizing Behavior: A Systematic Review and Search for Theoretical Mechanisms

Over the last decade, several candidate genes (i.e., MAOA, DRD4, DRD2, DAT1, 5-HTTLPR, and COMT) have been extensively studied as potential moderators of the detrimental effects of postnatal family adversity on child externalizing behaviors, such as aggression and conduct disorder. Many studies on such candidate gene by environment interactions (i.e., cG × E) have been published, and the first part of this paper offers a systematic review and integration of their findings (n = 53). The overview shows a set of heterogeneous findings. However, because of large differences between studies in terms of sample composition, conceptualizations, and power, it is difficult to determine if different findings indeed illustrate inconsistent cG × E findings or if findings are simply incomparable. In the second part of the paper, therefore, we argue that one way to help resolve this problem is the development of theory-driven a priori hypotheses on which biopsychosocial mechanisms might underlie cG × E. Such a theoretically based approach can help us specify our research strategies, create more comparable findings, and help us interpret different findings between studies. In accordance, we describe three possible explanatory mechanisms, based on extant literature on the concepts of (1) emotional reactivity, (2) reward sensitivity, and (3) punishment sensitivity. For each mechanism, we discuss the link between the putative mechanism and externalizing behaviors, the genetic polymorphism, and family adversity. Possible research strategies to test these mechanisms, and implications for interventions, are discussed.

Interacting effects of maternal responsiveness, infant regulatory problems and dopamine D4 receptor gene in the development of dysregulation during childhood: A longitudinal analysis

Recent longitudinal studies have indicated that affective and behavioral dysregulation in childhood is associated with an increased risk for various negative outcomes in later life. However, few studies to date have examined early mechanisms preceding dysregulation during early childhood. Aim of this study was to elucidate early mechanisms relating to dysregulation in later life using data from an epidemiological cohort study on the long-term outcome of early risk factors from birth to adulthood. At age 3 months, mothers and infants were videotaped during a nursing and playing situation. Maternal responsiveness was evaluated by trained raters. Infant regulatory problems were assessed on the basis of a parent interview and direct observation by trained raters. At age 8 and 11 years, 290 children (139 males) were rated on the Child Behavior Checklist (CBCL). Additionally, participants were genotyped for the dopamine D4 receptor (DRD4) exon 3 VNTR polymorphism. A significant three-way interaction between maternal responsiveness, DRD4 genotype and infant regulatory problems was detected predicting the CBCL-dysregulation profile (CBCL-DP). Carriers of the DRD4 7r allele with regulatory problems at age 3 months showed significantly more behavior problems associated with the CBCL-DP during childhood when exposed to less maternal responsiveness. In contrast, no effect of maternal responsiveness was observed in DRD4 7r carriers without infant regulatory problems and in non-carriers of the DRD4 7r allele. This prospective longitudinal study extends earlier findings regarding the association of the CBCL-DP with early parenting and later psychopathology, introducing both DRD4 genotype and infant regulatory problems as important moderators.

The Moderating Role of Genetics: The Effect of Length of Hospitalization on Children's Internalizing and Externalizing Behaviors

The study considered individual differences in children's ability to adjust to hospitalization and found the length of hospitalization to be related to adaptive psychological functioning for some children. Applying the theoretical framework of three competing models of gene-X-environment interactions (diathesis-stress, differential susceptibility, and vantage sensitivity), the study examined the moderating effect of genetics (DRD4) on the relationship between the length of hospitalization and internalizing and externalizing problems. Mothers reported on children's hospitalization background and conduct problems (externalizing) and emotional symptoms (internalizing), using subscales of the 25-item Strength and Difficulties Questionnaire (1). Data on both hospitalization and genetics were available for 65 children, 57% of whom were females, with an average age of 61.4 months (SD = 2.3). The study found length of hospitalization did not predict emotional and behavior problems per se, but the interaction with genetics was significant; the length of hospitalization was related to diminished levels of internalizing and externalizing problems only for children with the 7R allele (the sensitive variant). The vantage sensitivity model best accounted for how the length of hospitalization and genetics related to children's internalizing and externalizing problems.

The Generation R Study: Biobank update 2015

The Generation R Study is a population-based prospective cohort study from fetal life until adulthood. The study is designed to identify early environmental and genetic causes and causal pathways leading to normal and abnormal growth, development and health from fetal life, childhood and young adulthood. In total, 9,778 mothers were enrolled in the study. Data collection in children and their parents include questionnaires, interviews, detailed physical and ultrasound examinations, behavioural observations, Magnetic Resonance Imaging and biological samples. Efforts have been conducted for collecting biological samples including blood, hair, faeces, nasal swabs, saliva and urine samples and generating genomics data on DNA, RNA and microbiome. In this paper, we give an update of the collection, processing and storage of these biological samples and available measures. Together with detailed phenotype measurements, these biological samples provide a unique resource for epidemiological studies focused on environmental exposures, genetic and genomic determinants and their interactions in relation to growth, health and development from fetal life onwards.