Boys' serotonin transporter genotype affects maternal behavior through self-control: a case of evocative gene-environment correlation

Commentary: Assortative parenting and assortative cross-parenting: New views of parental preference for selected children

The commentary delves into the implications of "assortative parenting" and "assortative cross-parenting," as introduced by N. L. Segal, and situates these concepts within the framework of current research. It addresses the joys and complexities of raising twins, highlighting how their concurrent development stages can amplify parental favoritism and heighten the challenge of addressing each twin's unique needs. This interplay provides a rich context to investigate assortative parenting practices. Additionally, this paper contemplates the broader picture of twin studies, particularly how the care of monozygotic twins (who share 100 % of their genes) and dizygotic twins (who share 50 % of their genes, on average) may reveal the intertwined nature of genetics and environment in parenting strategies. It also proposes that twins' interactions with other family members, their spouses, and peers can offer profound insights into the phenomena of phenotypic assortative affiliation, enriching our understanding of close relational bonds.

The Special Role of Middle Childhood in Self-Control Development: Longitudinal and Genetic Evidence

Despite the importance of self-control for well-being and adjustment, its development from early childhood to early adolescence has been relatively understudied. We addressed the development of mother-reported self-control in what is likely the largest and longest longitudinal twin study of the topic to this day (N = 1,889 individual children with data from at least one of 5 waves: ages 3, 5, 6.5, 8-9 and 11 years). We examined rank-order change in self-control from early childhood to early adolescence, genetic and environmental contributions to variance in the trait and differential developmental trajectories. The relative contribution of genetic and environmental factors to change and stability was also examined. Results point at middle childhood as a period of potential transition and change. During this period the rank-order stability of self-control increases, heritability rates substantially rise, and a cross-over occurs in two of the self-control trajectories. Non-additive genetic effects contribute to both stability and change in self-control while the non-shared environment contributes mostly to change, with no effect for the shared environment. Our findings suggest that new genetic factors, that emerge around age 6.5 and whose effect on self-control is carried on along development, may partially account for changes in self-control around late middle childhood, and explain the growing stability in the trait approaching early adolescence. We discuss the implications of the special role of middle childhood for self-control development. This article is protected by copyright. All rights reserved.

Integrating the study of personality and psychopathology in the context of gene-environment correlations across development

OBJECTIVE

A key principle of individual differences research is that biological and environmental factors jointly influence personality and psychopathology. Genes and environments interact to influence the emergence and stability of both normal and abnormal behavior (i.e., genetic predisposition, X, is exacerbated or buffered under environmental conditions, Y, or vice versa), including by shaping the neural circuits underpinning behavior. The interplay of genes and environments is also reflected in various ways in which they are correlated (i.e., rGE). That is, the same genetic factors that give rise to personality or psychopathology also shape that person's environment.

METHODS

In this review, we outline passive, evocative, and active rGE processes and review the findings of studies that have addressed rGE in relation to understanding individual differences in personality and psychopathology across development.

RESULTS

Throughout, we evaluate the question of whether it is possible, not only to differentiate the person from their problems, but also to differentiate the person from their problems and their environment.

CONCLUSIONS

We provide recommendations for future research to model rGE and better inform our ability to study personality and psychopathology, while separating the influence of the environment.

Emotional-Behavioral Regulation, Temperament and Parent-Child Interactions Are Associated with Dopamine Transporter Allelic Polymorphism in Early Childhood: A Pilot Study

International research has highlighted the role played by individual genetic polymorphism, children’s emotional-behavioral functioning, and quality of parent–child feeding interaction in shaping children’s development. Few studies have focused on the dopamine transporter (DAT1) gene in these processes. In a community sample of 81 families with young children aged between 19 and 28 months (37 males and 44 females), this pilot study aimed to explore possible relationships between children’s DAT1 genotype (9/x: 9/9, 9/19 contrasted to 10/10), their own psychological profiles, parental psychopathological risk, and the quality of mother–child and father–child feeding interactions. Children’s DAT1 genotype was assessed collecting DNA through buccal; children’s temperament and emotional-behavioral regulation, and parental psychopathological risk were assessed, respectively, through report-form and self-report instruments; then, dyadic exchanges were videotaped during a mealtime, and coded based on the Scala di Valutazione dell′Interazione Alimentare (SVIA). Results showed significant differences in the variables under study based on children’s DAT1 genotype, with a higher risk associated with the 10/10. Our findings have provided preliminary new evidence on the relationship between a different child’s polymorphisms, their own emotional-behavioral functioning, and the quality of the family environment, with important implications for the planning of more targeted prevention programs.

The Longitudinal Israeli Study of Twins (LIST) Reaches Adolescence: Genetic and Environmental Pathways to Social, Personality and Moral Development

The Longitudinal Israeli Study of Twins (LIST) focuses on the developmental, genetic and environmental contributions to individual differences in children's and adolescents' social behavior. Key variables have been empathy, prosocial behavior, temperament and values. Another major goal of LIST has been to study gene-environment correlations, mainly concerning parenting. LIST includes 1657 families of Hebrew-speaking Israeli twins who have participated at least once in the study. Children's environment and their development are assessed in a multivariate, multimethod fashion, including observed, parent-reported and self-reported data. The current article summarizes and updates recent findings from LIST. For example, LIST provided evidence for the heritability of human values with the youngest sample to date, and the first genetic investigation of adolescents' identity formation. Finally, future aims of LIST are discussed.

Gene-environment correlations in parental emotional warmth and intolerance: genome-wide analysis over two generations of the Young Finns Study

BACKGROUND

Genomic analysis of the child might offer new potential to illuminate human parenting. We examined whether offspring (G2) genome-wide genotype variation (SNPs) is associated with their mother's (G1) emotional warmth and intolerance, indicating a gene-environment correlation. If this association is stronger than between G2's genes and their emotional warmth and intolerance toward their own children, then this would indicate the presence of an evocative gene-environment correlation. To further understand how G1 mother's parenting has been evoked by genetically influenced characteristics of the child (G2), we examined whether child (G2) temperament partially accounted for the association between offspring genes and parental responses.

METHODS

Participants were from the Young Finns Study. G1 mothers (N = 2,349; mean age 39 years) self-reported the emotional warmth and intolerance toward G2 in 1980 when the participants were from 3 to 18 years old. G2 participants answered the same parenting scales in 2007/2012 (N = 1,378; mean age = 38 years in 2007; 59% female) when their children were on average 11 years old. Offspring temperament traits were self-reported in 1992 (G2 age range 15-30 years). Estimation of the phenotypic variance explained by the SNPs of G2 was done by genome-wide complex trait analysis with restricted maximum likelihood (GCTA-GREML).

RESULTS

Results showed that the SNPs of a child (G2) explained 22.6% of the phenotypic variance of maternal intolerance (G1; p-value = .039). G2 temperament trait negative emotionality explained only 2.4% points of this association. G2 genes did not explain G1 emotional warmth or G2's own emotional warmth and intolerance. However, further analyses of a combined measure of both G1 parenting scales found genetic effects. Parent or child gender did not moderate the observed associations.

CONCLUSIONS

Presented genome-wide evidence is pointing to the important role a child plays in affecting and shaping his/her family environment, though the underlying mechanisms remain unclear.

Implicit associations to infant cry: Genetics and early care experiences influence caregiving propensities

Adults' sensitive appraisal of and response to infant cry play a foundational role in child development. Employing a gene × environment (G × E) approach, this study investigated the interaction of genetic polymorphisms of the serotonin transporter gene (5-HTTLPR) and oxytocin receptor genes (OXTR; rs53576, rs2254298) with early parental care experiences in influencing adults' implicit associations to infant cry. Eighty nulliparous adults (40 females, 40 males) responded to the Parental Acceptance-Rejection Questionnaire (PARQ), a measure of early care experiences, and participated in a Single Category Implicit Association Task (SC-IAT) to measure implicit associations to infant cry. Independent of parental experience, the valence of the implicit response to infant cry is associated with the serotonin transporter gene polymorphism (5-HTTLPR), with LL-carriers showing more positive implicit associations than S-carriers. OXTR rs53576 moderated the relation between parental rejection and implicit appraisal of infant cry: A-carriers who experienced negative early care showed an implicit positive appraisal of infant cry, whereas in GG carriers, positive early care experiences were associated with an implicit positive reaction to infant cry. OXTR rs2254298 had no relation to implicit associations to infant cry or to early care experiences. These findings cast light on the possible interplay of genetic inheritance and early environment in influencing adults' responses to infant cry that may be incorporated into screening protocols aimed at identifying at-risk adult-infant interactions.

Gene-environment correlations in the cross-generational transmission of parenting: Grandparenting moderates the effect of child 5-HTTLPR genotype on mothers' parenting

Evidence suggests that parenting is associated cross-generationally and that children's genes may elicit specific parenting styles (evocative gene-environment correlation). This study examined whether the effect of children's genotype, specifically 5-HTTLPR, on mothers' parenting behaviors was moderated by her own parenting experiences from her mother. Two independent samples of three-year-olds (N = 476 and 405) were genotyped for the serotonin transporter gene, and observational measures of parenting were collected. Mothers completed measures of the parenting they received as children. The child having a short allele on 5-HTTLPR was associated with more maternal hostility (sample 1 and 2) and with less maternal support (sample 1), but only if the mother reported lower quality grandmothers' parenting (abuse and indifference in Sample 1 and lower levels of grandmother care in Sample 2). Results support the possibility of a moderated evocative gene-environment correlation.

Sometimes It's Good to be Short: The Serotonin Transporter Gene, Positive Parenting, and Adolescent Depression

In threatening environments, the short (S) allele of 5-HTTLPR is proposed to augment risk for depression. However, it is unknown whether 5-HTTLPR variation increases risk for depression in environments of deprivation, lacking positive or nurturant features. Two independent longitudinal studies (n = 681 and 176, respectively) examined whether 5-HTTLPR moderated associations between low levels of positive parenting at 11-13 years and subsequent depression at 17-19 years. In both studies only LL homozygous adolescents were at greater risk for depression with decreasing levels of positive parenting. Thus, while the S allele has previously been identified as a susceptible genotype, these findings suggest that the L allele may also confer sensitivity to depression in the face of specific environmental challenges.

Parenting and the development of effortful control from early childhood to early adolescence: A transactional developmental model

Poor effortful control is a key temperamental factor underlying behavioral problems. The bidirectional association of child effortful control with both positive parenting and negative discipline was examined from ages approximately 3 to 13-14 years, involving five time points, and using data from parents and children in the Oregon Youth Study-Three Generational Study (N = 318 children from 150 families). Based on a dynamic developmental systems approach, it was hypothesized that there would be concurrent associations between parenting and child effortful control and bidirectional effects across time from each aspect of parenting to effortful control and from effortful control to each aspect of parenting. It was also hypothesized that associations would be more robust in early childhood, from ages 3 to 7 years, and would diminish as indicated by significantly weaker effects at the older ages, 11-12 to 13-14 years. Longitudinal feedback or mediated effects were also tested. The findings supported (a) stability in each construct over multiple developmental periods; (b) concurrent associations, which were significantly weaker at the older ages;

Affiliation with substance-using peers: Examining gene-environment correlations among parent monitoring, polygenic risk, and children's impulsivity

Parental monitoring can buffer the effect of deviant peers on adolescents' substance use by reducing affiliation with substance-using peers. However, children's genetic predispositions may evoke poorer monitoring, contributing to negative child outcomes. We examined evocative genotype-environment correlations underlying children's genetic predisposition for behavioral undercontrol and parental monitoring in early adolescence via children's impulsivity in middle childhood, and the influence of parental monitoring on affiliation with substance-using peers a year and a half later (n = 359). Genetic predisposition for behavioral undercontrol was captured using a polygenic risk score, and a portion of passive rGE was controlled by including parents' polygenic risk scores. Children's polygenic risk predicted poorer parental monitoring via greater children's impulsivity, indicating evocative rGE, controlling for a portion of passive rGE. Poorer parental monitoring predicted greater children's affiliation with substance-using peers a year and a half later. Results are discussed with respect to gene-environment correlations within developmental cascades.

Roles of Response Inhibition and Gene-Environment Interplay in Pathways to Adolescents' Externalizing Problems

This study used two waves of data to investigate pathways through which adolescents' response inhibition related to later externalizing problems. A polygenic risk score indexed genetic risk for poor response inhibition. Adolescents' performance on a response inhibition task mediated the relation between adolescents' polygenic risk scores and mother's inconsistent parenting (i.e., evocative rGE), even after controlling for mothers' genetic risk (i.e., passive rGE). Mothers' inconsistent parenting subsequently prospectively predicted adolescents' externalizing problems. Adolescents' response inhibition also prospectively predicted later externalizing behaviors. These findings were subgroup-specific, with greater risk for non-Hispanic Caucasian boys with substance-disordered parents. Results suggest that poor response inhibition may increase risk for adolescents' externalizing problems both directly and by evoking certain environmental conditions.

The Drosophila foraging gene human orthologue PRKG1 predicts individual differences in the effects of early adversity on maternal sensitivity

There is variation in the extent to which childhood adverse experience affects adult individual differences in maternal behavior. Genetic variation in the animal foraging gene, which encodes a cGMP-dependent protein kinase, contributes to variation in the responses of adult fruit flies, Drosophila melanogaster, to early life adversity and is also known to play a role in maternal behavior in social insects. Here we investigate genetic variation in the human foraging gene (PRKG1) as a predictor of individual differences in the effects of early adversity on maternal behavior in two cohorts. We show that the PRKG1 genetic polymorphism rs2043556 associates with maternal sensitivity towards their infants. We also show that rs2043556 moderates the association between self-reported childhood adversity of the mother and her later maternal sensitivity. Mothers with the TT allele of rs2043556 appeared buffered from the effects of early adversity, whereas mothers with the presence of a C allele were not. Our study used the Toronto Longitudinal Cohort (N=288 mother-16 month old infant pairs) and the Maternal Adversity and Vulnerability and Neurodevelopment Cohort (N=281 mother-18 month old infant pairs). Our findings expand the literature on the contributions of both genetics and gene-environment interactions to maternal sensitivity, a salient feature of the early environment relevant for child neurodevelopment.

Predicting substance use in emerging adulthood: A genetically informed study of developmental transactions between impulsivity and family conflict

Deviance proneness models propose a multilevel interplay in which transactions among genetic, individual, and family risk factors place children at increased risk for substance use. We examined bidirectional transactions between impulsivity and family conflict from middle childhood to adolescence and their contributions to substance use in adolescence and emerging adulthood (n = 380). Moreover, we examined children's, mothers', and fathers' polygenic risk scores for behavioral undercontrol, and mothers' and fathers' interparental conflict and substance disorder diagnoses as predictors of these transactions. The results support a developmental cascade model in which children's polygenic risk scores predicted greater impulsivity in middle childhood. Impulsivity in middle childhood predicted greater family conflict in late childhood, which in turn predicted greater impulsivity in late adolescence. Adolescent impulsivity subsequently predicted greater substance use in emerging adulthood. Results are discussed with respect to evocative genotype-environment correlations within developmental cascades and applications to prevention efforts.

Parental Serotonin Transporter Polymorphism (5-HTTLPR) Moderates Associations of Stress and Child Behavior With Parenting Behavior

The serotonin transporter-linked polymorphic region (5-HTTLPR) is associated with caregiving in nonhuman animals and with affective and cognitive correlates of human parenting, yet its association with human parenting is largely unknown. Using a well-characterized sample of parents and offspring, we evaluated the association of parental 5-HTTLPR with observed positive and negative parenting behavior, as well as its biologically plausible moderation of child-related stress and disruptive child behavior as predictors of parenting. One hundred and sixty-two parents (86% mothers) and their 6- to 9-year-old children with and without attention-deficit/hyperactivity disorder were ascertained using multiple methods including structured interviews, rating scales, and observed parent-child interaction, yielding strong measures of key constructs. Controlling for multiple youth-level (e.g., sex, 5-HTTLPR genotype, disruptive behavior) and parent-level (e.g., demographics, depression, attention-deficit/hyperactivity disorder) factors, parents with an S allele exhibited significantly less observed positive parenting than those with the LL genotype. Significant Gene × Environment interactions were also observed: Child-related stress was negatively associated with observed parental negativity among SS/SL genotype parents but not LL genotype parents; next, observed disruptive child behavior was positively associated with parental negativity for both genotypes, but the effect was strongest in SS/SL parents. These preliminary findings suggest that parental 5-HTTLPR is uniquely associated with positive and negative parenting behavior, with more specific patterns according to child-related stress and disruptive child behavior. We consider implications for future research evaluating genetic influences on parenting as well as considerations for designing and delivering parenting-based interventions.

Genetic mechanisms of parenting

This article is part of a Special Issue "Parental Care". The complexities of parenting behavior in humans have been studied for decades. Only recently did we begin to probe the genetic and epigenetic mechanisms underlying these complexities. Much of the research in this field continues to be informed by animal studies, where genetic manipulations and invasive tools allow to peek into and directly observe the brain during the expression of maternal behavior. In humans, studies of adult twins who are parents can suggest dimensions of parenting that might be more amenable to a genetic influence. Candidate gene studies can test specific genes in association with parental behavior based on prior knowledge of those genes' function. Gene-by-environment interactions of a specific kind indicating differential susceptibility to the environment might explain why some parents are more resilient and others are more vulnerable to stressful life events. Epigenetic studies can provide the bridge often necessary to explain why some individuals behave differently from others despite common genetic influences. There is a much-needed expansion in parenting research to include not only mothers as the focus-as has been the case almost exclusively to date-but also fathers, grandparents, and other caregivers.

Externalizing symptoms, effortful control, and intrusive parenting: A test of bidirectional longitudinal relations during early childhood

At approximately 30, 42, and 54 months of age (N = 231), the relations among children's externalizing symptoms, intrusive maternal parenting, and children's effortful control (EC) were examined. Both intrusive parenting and low EC have been related to psychopathology, but children's externalizing problems and low EC might affect the quality of parenting and one another. Mothers’ intrusive behavior with their children was assessed with observations, children's EC was measured with mothers’ and caregivers’ reports, and children's externalizing symptoms were assessed with mothers’, fathers’, and caregivers’ reports. In a structural equation panel model, bidirectional relations between intrusive parenting and EC were found: EC at 30 and 42 months predicted low levels of intrusive parenting a year later, controlling for prior levels of parenting and vice versa. Moreover, high levels of children's externalizing problems at both 30 and 42 months negatively predicted EC a year later, controlling for prior levels of EC. Although externalizing problems positively predicted high EC over time, this appeared to be a suppression effect because these variables had a strong negative pattern in the zero-order correlations. Moreover, when controlling for the stability of intrusive parenting, EC, and externalizing (all exhibited significant stability across time) and the aforementioned cross-lagged predictive paths, EC and externalizing problems were still negatively related within the 54-month assessment. The findings are consistent with the view that children's externalizing behavior undermines their EC and contributes to intrusive mothering and that relations between intrusive parenting and EC are bidirectional across time. Thus, interventions that focus on modifying children's externalizing problems (as well as the quality of parenting) might affect the quality of parenting they receive and, hence, subsequent problems with adjustment.

Child effects and child care: Implications for risk and adjustment

Evocative effects of child characteristics on the quality and quantity of child care were assessed in two studies using longitudinal data from the NICHD Study of Early Child Care. We focus on the influence of child characteristics on two important aspects of the child care experience: language stimulation provided by caregivers and quantity of care. In Study 1, associations between the developmental status of children aged 15 to 54 months and the language stimulation provided by their caregivers were examined using path models, and longitudinal child effects were detected across the earliest time points of the study. In Study 2, the associations among child behavior, temperament, development, and time in care were examined. Little evidence was found for such child effects on time in care. The results are discussed in terms of the effects of child care on child development and implications for developmental processes, particularly for children at greatest risk for developmental delay or psychopathology.

Genetic Influences on Peer and Family Relationships Across Adolescent Development: Introduction to the Special Issue

Nearly all aspects of human development are influenced by genetic and environmental factors, which conjointly shape development through several gene-environment interplay mechanisms. More recently, researchers have begun to examine the influence of genetic factors on peer and family relationships across the pre-adolescent and adolescent time periods. This article introduces the special issue by providing a critical overview of behavior genetic methodology and existing research demonstrating gene-environment processes operating on the link between peer and family relationships and adolescent adjustment. The overview is followed by a summary of new research studies, which use genetically informed samples to examine how peer and family environment work together with genetic factors to influence behavioral outcomes across adolescence. The studies in this special issue provide further evidence of gene-environment interplay through innovative behavior genetic methodological approaches across international samples. Results from the quantitative models indicate environmental moderation of genetic risk for coercive adolescent-parent relationships and deviant peer affiliation. The molecular genetics studies provide support for a gene-environment interaction differential susceptibility model for dopamine regulation genes across positive and negative peer and family environments. Overall, the findings from the studies in this special issue demonstrate the importance of considering how genes and environments work in concert to shape developmental outcomes during adolescence.

Involvement of serotonin transporter gene polymorphisms (5-HTT) in impulsive behavior in the japanese population

The serotonergic pathway has been implicated in the pathogenesis of impulsivity, and sensitivity to aversive outcomes may be linked to serotonin (5-HT) levels. Polymorphisms in the gene that encodes the serotonin transporter (5-HTT), which have differential effects on the level of serotonin transmission, display alternate responses to aversive stimuli. However, recent studies have shown that 5-HT does not affect motor function, which suggests that the functioning of the serotonin-transporter-linked polymorphic region (5-HTTLPR) does not directly affect the behavioral regulatory process itself, but instead exerts an effect via the evaluation of the potential risk associated with particular behavioral outputs. The aim of the present study was to examine the effect of specific 5-HTTLPR genotypes on the motor regulatory process, as observed during a Go/Nogo punishment feedback task. 5-HTT gene-linked promoter polymorphisms were analyzed by polymerase chain reaction, using lymphocytes from 61 healthy Japanese volunteers. Impulsivity was defined as the number of commission errors (responding when one should not) made during a Go/Nogo task. We found that the s/s genotype group made fewer impulsive responses, specifically under aversive conditions for committing such errors, compared to those in the s/l group, without affecting overall motor inhibition. These results suggest that 5-HTTLPRs do not directly affect the behavioral regulatory process itself, but may instead exert an effect on the evaluation of potential risk. The results also indicate that under such aversive conditions, decreased expression of 5-HTT may promote motor inhibitory control.

Parenting as a reaction evoked by children's genotype: a meta-analysis of children-as-twins studies

Parenting has been extensively studied but mostly as a causal factor influencing child outcomes. The aim of the current article is to examine the child's side of the relationship by meta-analyzing studies which used quantitative genetic methods that provide leverage in understanding causality. A meta-analysis of 32 children-as-twins studies of parenting revealed a heritability estimate of 23%, thus indicating that genetically influenced behaviors of the child affect and shape parental behavior. The shared- and nonshared-environmental estimates, which amounted to 43% and 34%, respectively, indicate not only substantial consistency in parental behavior but also differential treatment within the family. Assessment method, age, and parenting dimension were found to be significant moderators of these influences. Our findings stress the importance of accounting for genotype-environment correlations in child-development studies and call into question previous research that interpreted correlational results in unidirectional terms with parenting as the sole causal factor.

Gene–environment correlation in developmental psychopathology

Modern research acknowledges that psychopathology and individual differences in normal development are the joint products of both biological and social influences. Although there have been numerous publications on Gene × Environment interactions in the past decade, gene–environment correlation is another important form of gene–environment interplay that has received less attention. This Special Section demonstrates, using a range of methodological approaches, the importance of gene–environment correlation in developmental psychopathology. Several types of gene–environment correlation are described, including passive, evocative, and active. Other studies highlight the potential for gene–environment correlation to obscure associations between risk exposures and child psychopathology. Future directions for gene–environment correlation research are discussed.

The Longitudinal Israeli Study of Twins (LIST)—An Integrative View of Social Development

The Longitudinal Israeli Study of Twins (LIST) is a social developmental study, which implements social-developmental, molecular genetic, epigenetic, and behavioral genetic methods to advance knowledge on the development of individual differences in social behavior. Twins are followed from the age of three and both observational and parental-questionnaire data are collected on their empathy, temperament, and pro-social behavior. The parenting styles of parents are also evaluated using self-reports and observations and DNA samples are collected from parents and twins. In the current paper, we provide a review of our recent work and discuss the future aims of the LIST.