The genetic epidemiology of parental discipline

Estimating the Heritability of Experiencing Child Maltreatment in an Extended Family Design

Child-driven genetic factors can contribute to negative parenting and may increase the risk of being maltreated. Experiencing childhood maltreatment may be partly heritable, but results of twin studies are mixed. In the current study, we used a cross-sectional extended family design to estimate genetic and environmental effects on experiencing child maltreatment. The sample consisted of 395 individuals (225 women; M_age = 38.85 years, range_age = 7-88 years) from 63 families with two or three participating generations. Participants were oversampled for experienced maltreatment. Self-reported experienced child maltreatment was measured using a questionnaire assessing physical and emotional abuse, and physical and emotional neglect. All maltreatment phenotypes were partly heritable with percentages for h² ranging from 30% (SE = 13%) for neglect to 62% (SE = 19%) for severe physical abuse. Common environmental effects (c²) explained a statistically significant proportion of variance for all phenotypes except for the experience of severe physical abuse (c² = 9%, SE = 13%, p = .26). The genetic correlation between abuse and neglect was ρ_g = .73 (p = .02). Common environmental variance increased as socioeconomic status (SES) decreased (p = .05), but additive genetic and unique environmental variances were constant across different levels of SES.

The genetic and environmental etiology of child maltreatment in a parent-based extended family design

Child maltreatment has been associated with various cumulative risk factors. However, little is known about the extent to which genetic and environmental factors contribute to individual differences between parents in perpetrating child maltreatment. To estimate the relative contribution of genetic and environmental factors to perpetrating maltreatment we used a parent-based extended family design. Child-reported perpetrated maltreatment was available for 556 parents (283 women) from 63 families. To explore reporter effects (i.e., child perspective on maltreatment), child reports were compared to multi-informant reports. Based on polygenic model analyses, most of the variance related to the perpetration of physical abuse and emotional neglect was explained by common environmental factors (physical abuse: c2 = 59%, SE = 12%, p = .006; emotional neglect: c2 = 47%, SE = 8%, p < .001) whereas genetic factors did not significantly contribute to the model. For perpetrated emotional abuse, in contrast, genetic factors did significantly contribute to perpetrated emotional abuse (h2 = 33%, SE = 8%, p < .001), whereas common environment factors did not. Multi-informant reports led to similar estimates of genetic and common environmental effects on all measures except for emotional abuse, where a multi-informant approach yielded higher estimates of the common environmental effects. Overall, estimates of unique environment, including measurement error, were lower using multi-informant reports. In conclusion, our findings suggest that genetic pathways play a significant role in perpetrating emotional abuse, while physical abuse and emotional neglect are transmitted primarily through common environmental factors. These findings imply that interventions may need to target different mechanisms dependings on maltreatment type.

Childhood adversities, bonding, and personality in social anxiety disorder with alcohol use disorder

Social anxiety disorder (SAD) is frequently associated with alcohol use disorders (abuse/dependence). However, there has been little research on the characteristics of this subgroup so far. In the current study we investigated individuals with SAD and comorbid alcohol use disorder (AUD) with regard to socialization experiences and personality. The sample comprised 410 individuals diagnosed with SAD by the Structured Clinical Interview of DSM-IV. 108 participants with comorbid AUD were compared to 302 participants without comorbid AUD concerning traumatic experiences during childhood and adolescence (Adverse Childhood Experiences Questionnaire; ACE), parental bonding (Parental Bonding Instrument; PBI), and personality (Temperament and Character Inventory; TCI). MANCOVA with covariates sex and depression displayed that individuals with SAD plus AUD reported significantly more traumatic events during childhood and adolescence, lower levels of maternal care, as well as lower cooperativeness. Our results highlight that adverse childhood experiences and unfavourable maternal bonding characterize individuals suffering from SAD plus AUD. These experiences might be reflected in a personality-based tendency to distance themselves from others, which corresponds to low scores on the character dimension cooperativeness. A deeper understanding of personality and specific socialization experiences is necessary to develop new treatment options in this clinically challenging subgroup.

Predicting the use of corporal punishment: Child aggression, parent religiosity, and the BDNF gene

Corporal punishment (CP) has been associated with deleterious child outcomes, highlighting the importance of understanding its underpinnings. Although several factors have been linked with parents' CP use, genetic influences on CP have rarely been studied, and an integrative view examining the interplay between different predictors of CP is missing. We focused on the separate and joint effects of religiosity, child aggression, parent's gender, and a valine (Val) to methionine (Met) substitution in the brain-derived neurotrophic factor (BDNF) gene. Data came from a twin sample (51% male, aged 6.5 years). We used mothers' and fathers' self-reports of CP and religiosity, and the other parent's report on child aggression. Complete data were available for 244 mothers and their 466 children, and for 217 fathers and their 409 children. The random split method was employed to examine replicability. For mothers, only the effect of religiosity appeared to replicate. For fathers, several effects predicting CP use replicated in both samples: child aggression, child sex, religiosity, and a three-way (GxExE) interaction implicating fathers' BDNF genotype, child aggression and religiosity. Religious fathers who carried the Met allele and had an aggressive child used CP more frequently; in contrast, secular fathers' CP use was not affected by their BDNF genotype or child aggression. Results were also repeated longitudinally in a subsample with age 8-9 data. Findings highlight the utility of a bio-ecological approach for studying CP use by shedding light on pertinent gene-environment interaction processes. Possible implications for intervention and public policy are discussed.

Etiological Influences on Perceptions of Parenting: A Longitudinal, Multi-Informant Twin Study

Children and their parents often differ in their perception of the relationship they share. As this relationship changes developmentally, the nature of these differences may also change. Longitudinal genetic designs can be used to investigate the developmental etiologies of shared and distinct perceptions. In this study, we used longitudinal psychometric models to analyze child and parent reports of negative parenting for 6417 twin pairs from the Twins Early Development Study at ages 9, 12 and 14 years. Within-time cross-reporter correlations, indicating the degree to which children and parents perceived negative parenting behaviors similarly at each age, were moderate (r = .44 - .46). Longitudinal genetic analyses revealed these shared perceptions to be relatively stable during the transition into adolescence, with this stability driven by a combination of children's genetic factors and family-wide environmental factors. In contrast, child- and parent-specific perceptions of parenting were predominantly age-specific, a developmental pattern underpinned by child genetic factors and a combination of family-wide and unique environmental influences. These results and their implications are discussed in the context of interplay between reciprocal interactions, subjective insight and developmental behavioral change in the parent-child relationship.

Mothers' power assertion; children's negative, adversarial orientation; and future behavior problems in low-income families: early maternal responsiveness as a moderator of the developmental cascade

Parental power assertion, a key dimension of family environment, generally sets in motion detrimental developmental cascades; however, evidence suggests that other qualities of parenting, such as responsiveness, can significantly moderate those processes. Mechanisms that account for such moderating effects are not fully understood. We propose a conceptual model of processes linking parental power assertion, parental responsiveness, children's negative, adversarial, rejecting orientation toward the parent, and behavior problems. We test that model in a short-term longitudinal design involving 186 low-income, ethnically diverse mothers and their toddlers. When children were 30 months, the dyads were observed in multiple, lengthy, naturalistic laboratory interactions to assess behaviorally mothers' responsiveness and their power-assertive control style. At 33 months, we observed behavioral indicators of children's negative, adversarial, rejecting orientation toward the mothers in several naturalistic and standardized paradigms. At 40 months, mothers rated children's behavior problems. The proposed moderated mediation sequence, tested using a new approach, PROCESS (Hayes, 2013), was supported. The indirect effect from maternal power assertion to children's negative, adversarial orientation to future behavior problems was present when mothers' responsiveness was either low or average but absent when mothers were highly responsive. This study elucidates a potential process that may link parental power assertion with behavior problems and highlights how positive aspects of parenting can moderate this process and defuse maladaptive developmental cascades. It also suggests possible targets for parenting intervention and prevention efforts.

Sexually coercive behavior following childhood maltreatment

Child maltreatment is associated with adult sexually coercive behavior. The association may be causal or confounders that increase the risk of both childhood victimization and sexually coercive behavior might explain the observed links. We examined if childhood maltreatment was related to sexual coercion independently of familial (genetic or common family environment) risk factors, thereby addressing potential causality. Participants were 6,255 18 to 33-year-old twins from the Finnish population-based study "Genetics of Sex and Aggression" who responded to self-report questionnaires of child maltreatment and sexually coercive behavior. We used generalized estimating equations to elucidate risk of sexual coercion in maltreated compared to unrelated, non-maltreated individuals. To adjust for unmeasured familial factors, we used the co-twin control method and compared sexual coercion risk within maltreatment-discordant twin pairs. Further, we examined possible differential effects of maltreatment subtypes and compared mean differences in maltreatment summary scores between sexually coercive individuals and controls. Sexual coercion was moderately more common among individuals maltreated as children versus unrelated controls (38.3 vs. 22.8 %; age- and gender-adjusted odds ratio, aOR = 2.31, 95 % CI 1.75-3.05) and the risk increase remained similar within maltreatment-discordant twins (OR = 2.82, 95 % CI 1.42-5.61). Moreover, different maltreatment subtypes predicted sexual coercion equally well and effect sizes remained similar within discordant twin pairs. We conclude that associations between child maltreatment and sexual coercion are largely independent of shared familial confounds, consistent with a causal inference. Importantly, detection and targeted interventions for maltreated children should remain a priority to reduce societal sexually coercive behavior.

Origins of children's externalizing behavior problems in low-income families: toddlers' willing stance toward their mothers as the missing link

Although children's active role in socialization has been long acknowledged, relevant research has typically focused on children's difficult temperament or negative behaviors that elicit coercive and adversarial processes, largely overlooking their capacity to act as positive, willing, even enthusiastic, active socialization agents. We studied the willing, receptive stance toward their mothers in a low-income sample of 186 children who were 24 to 44 months old. Confirmatory factor analysis supported a latent construct of willing stance, manifested as children's responsiveness to mothers in naturalistic interactions, responsive imitation in teaching contexts, and committed compliance with maternal prohibitions, all observed in the laboratory. Structural equation modeling analyses confirmed that ecological adversity undermined maternal responsiveness, and responsiveness, in turn, was linked to children's willing stance. A compromised willing stance predicted externalizing behavior problems, assessed 10 months later, and fully mediated the links between maternal responsiveness and those outcomes. Ecological adversity had a direct, unmediated effect on internalizing behavior problems. Considering children's active role as willing, receptive agents capable of embracing parental influence can lead to a more complete understanding of detrimental mechanisms that link ecological adversity with antisocial developmental pathways. It can also inform research on the normative socialization process, consistent with the objectives of developmental psychopathology.

Parenting and risk for mood, anxiety and substance use disorders: a study in population-based male twins

BACKGROUND

Previous studies consistently identified a relationship between parenting behavior and psychopathology. In this study, we extended prior analyses performed in female twins to a large sample of twins from male-male pairs.

METHODS

We used interview data on 2,609 adult male twins from a population-based twin registry. We examined the association between three retrospectively reported parenting dimensions (coldness, protectiveness, and authoritarianism) and lifetime history of seven common psychiatric and substance use disorders. Using univariate structural equation modeling, we also examined the influence of the genetic and environmental factors on parenting.

RESULTS

Examined individually, coldness was consistently associated with risk for a broad range of adult psychopathology. Averaged odds of psychiatric disorders associated with parenting were increased between 26 and 36 %. When the three parenting dimensions were examined together, coldness remained significant for major depression, phobia, and generalized anxiety disorder. Controlling for other disorders, the associations between the parenting dimensions and psychopathology were non-specific. Twin fitting model demonstrated that modest heritability accounted for parenting, whereas most variance resulted from the non-shared environment.

CONCLUSIONS

Based on our current and prior findings, there is broad similarity in the impact of parenting on adult psychopathology between men and women.

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 the development of adolescent substance abuse: selection effects of child personality and mediation via contextual risk factors

We used a longitudinal twin design to examine selection effects of personality traits at age 11 on high-risk environmental contexts at age 14 and the extent to which these contexts mediated risk for substance abuse at age 17. Socialization at age 11 (willingness to follow rules and endorse conventional values) predicted exposure to contextual risk at age 14. Contextual risk partially mediated the effect of socialization on substance abuse, though socialization also had a direct effect. In contrast, boldness at age 11 (social engagement and assurance, thrill seeking, and stress resilience) also predicted substance abuse directly but was unrelated to contextual risk. There was substantial overlap in the genetic and shared environmental influences on socialization and contextual risk, and genetic risk in socialization contributed to substance abuse indirectly via increased exposure to contextual risk. This suggests that active gene-environment correlations related to individual differences in socialization contributed to an early, high-risk developmental trajectory for adolescent substance abuse. In contrast, boldness appeared to index an independent and direct genetic risk factor for adolescent substance abuse.

The implications of genotype-environment correlation for establishing causal processes in psychopathology

The significance of genotype-environment interplay is its focus on how causal factors, whether environmental or genetic, have their effects. It is difficult to establish causality in observational research because of the potential for reverse causation and confounding. Most environmental measures are heritable, which means that their effects on the risk for psychopathology are potentially confounded by genotype. In contrast, genetic influences on psychopathology may be mediated by their effect on environmental exposures. The existence of genetic influences on putative environmental risk factors offers both possibilities and pitfalls for research into environmental epidemiology. We use the example of parenting and its influence on childhood externalizing problems to review how genotype-environment correlations can be exploited to demonstrate causal processes in pyschopathology.

Evocative gene-environment correlation in the mother-child relationship: a twin study of interpersonal processes

The behavior genetic literature suggests that genetically influenced characteristics of the child elicit specific behaviors from the parent. However, little is known about the processes by which genetically influenced child characteristics evoke parental responses. Interpersonal theory provides a useful framework for identifying reciprocal behavioral processes between children and mothers. The theory posits that, at any given moment, interpersonal behavior varies along the orthogonal dimensions of warmth and control and that the interpersonal behavior of one individual tends to elicit corresponding or contrasting behavior from the other (i.e., warmth elicits warmth, whereas control elicits submission). The current study thus examined these dimensions of interpersonal behavior as they relate to the parent-child relationship in 546 twin families. A computer joystick was used to rate videos of mother-child interactions in real time, yielding information on mother and child levels of warmth and control throughout the interaction. Analyses indicated that maternal control, but not maternal warmth, was influenced by evocative gene-environment correlational processes, such that genetic influences on maternal control and child control were largely overlapping. Moreover, these common genetic influences were present both cross-sectionally and over the course of the interaction. Such findings not only confirm the presence of evocative gene-environment correlational processes in the mother-child relationship but also illuminate at least one of the specific interpersonal behaviors that underlie this evocative process.

Challenging circumstances moderate the links between mothers' personality traits and their parenting in low-income families with young children

The need for research on potential moderators of personality-parenting links has been repeatedly emphasized, yet few studies have examined how varying stressful or challenging circumstances may influence such links. We studied 186 diverse, low-income mother-toddler dyads. Mothers described themselves in terms of Big Five traits, were observed in lengthy interactions with their children, and provided parenting reports. Ecological adversity, assessed as a cumulative index of known risk factors, and the child's difficulty observed as negative affect and defiance in interactions with mothers were posited as sources of parenting challenge. Mothers high in Neuroticism reported more power assertion. Some personality-parenting relations emerged only under challenging conditions. For mothers raising difficult children, higher Extraversion was linked to increased observed power assertion, but higher Conscientiousness was linked to decreased reported power assertion. There were no such relations for mothers of easy children. By contrast, some relations emerged only in the absence of challenge. Agreeableness was associated with more positive parenting for mothers who lived under conditions of low ecological adversity, and with less reported power for those who had easy children, and Openness was linked to more positive parenting for mothers of easy children. Those traits were unrelated to parenting under challenging conditions.

From correlates to causes: can quasi-experimental studies and statistical innovations bring us closer to identifying the causes of antisocial behavior?

Longitudinal, epidemiological studies have identified robust risk factors for youth antisocial behavior, including harsh and coercive discipline, maltreatment, smoking during pregnancy, divorce, teen parenthood, peer deviance, parental psychopathology, and social disadvantage. Nevertheless, because this literature is largely based on observational studies, it remains unclear whether these risk factors have truly causal effects. Identifying causal risk factors for antisocial behavior would be informative for intervention efforts and for studies that test whether individuals are differentially susceptible to risk exposures. In this article, we identify the challenges to causal inference posed by observational studies and describe quasi-experimental methods and statistical innovations that may move researchers beyond discussions of risk factors to allow for stronger causal inference. We then review studies that used these methods, and we evaluate whether robust risk factors identified from observational studies are likely to play a causal role in the emergence and development of youth antisocial behavior. There is evidence of causal effects for most of the risk factors we review. However, these effects are typically smaller than those reported in observational studies, suggesting that familial confounding, social selection, and misidentification might also explain some of the association between risk exposures and antisocial behavior. For some risk factors (e.g., smoking during pregnancy, parent alcohol problems), the evidence is weak that they have environmentally mediated effects on youth antisocial behavior. We discuss the implications of these findings for intervention efforts to reduce antisocial behavior and for basic research on the etiology and course of antisocial behavior.

Early childhood cognitive development and parental cognitive stimulation: evidence for reciprocal gene-environment transactions

Parenting is traditionally conceptualized as an exogenous environment that affects child development. However, children can also influence the quality of parenting that they receive. Using longitudinal data from 650 identical and fraternal twin pairs, we found that, controlling for cognitive ability at age 2 years, cognitive stimulation by parents (coded from video recorded behaviors during a dyadic task) at 2 years predicted subsequent reading ability at age 4 years. Moreover, controlling for cognitive stimulation at 2 years, children's cognitive ability at 2 years predicted the quality of stimulation received from their parents at 4 years. Genetic and environmental factors differentially contributed to these effects. Parenting influenced subsequent cognitive development through a family-level environmental pathway, whereas children's cognitive ability influenced subsequent parenting through a genetic pathway. These results suggest that genetic influences on cognitive development occur through a transactional process, in which genetic predispositions lead children to evoke cognitively stimulating experiences from their environments.

The association between conduct problems and maltreatment: testing genetic and environmental mediation

It is often assumed that childhood maltreatment causes conduct problems via an environmentally mediated process. However, the association may be due alternatively to either a nonpassive gene-environment correlation, in which parents react to children's genetically-influenced conduct problems by maltreating them, or a passive gene-environment correlation, in which parents' tendency to engage in maltreatment and children's conduct problems are both influenced by a hereditary vulnerability to antisocial behavior (i.e. genetic mediation). The present study estimated the contribution of these processes to the association between maltreatment and conduct problems. Bivariate behavior genetic analyses were conducted on approximately 1,650 twin and sibling pairs drawn from a large longitudinal study of adolescent health (Add Health). The correlation between maltreatment and conduct problems was small; much of the association between maltreatment and conduct problems was due to a nonpassive gene-environment correlation. Results were more consistent with the hypothesis that parents respond to children's genetically-influenced conduct problems by maltreating them than the hypothesis that maltreatment causes conduct problems.

Interplay of Genetic Risk Factors and Parent Monitoring in Risk for Nicotine Dependence

BACKGROUND: Several studies have found replicable associations between nicotine dependence and specific variants in the nicotinic receptor genes CHRNA5(rs16969968) and CHRNA3(rs3743078). How these newly identified genetic risks combine with known environmental risks is unknown. This study examined whether the level of parent monitoring during early adolescence modified the risk of nicotine dependence associated with these genetic variants. METHODS: In a cross-sectional case control study of US-based community sample of 2027 subjects, we use a systematic series of regression models to examine the effect of parent monitoring on risk associated with two distinct variants in the nicotinic receptor genes CHRNA5(rs16969968) and CHRNA3(rs3743078). RESULTS: Low parent monitoring as well as the previously identified genetic variants were associated with an increased risk of nicotine dependence. An interaction was found between the SNP(rs16969968) and parent monitoring (p=0.034). The risk for nicotine dependence increased significantly with the risk genotype of SNP(rs16969968) when combined with lowest quartile parent monitoring. In contrast, there was no evidence of an interaction between SNP(rs3743078) and parent monitoring (p=0.80). CONCLUSIONS: The genetic risk of nicotine dependent associated with rs16969968 was modified by level of parent monitoring, while the genetic risk associated with rs3743078 was not, suggesting that the increased risk due to some genes may be mitigated by environmental factors such as parent monitoring.

Parental socialization and adolescents' alcohol use behaviors: predictive disparities in parents' versus adolescents' perceptions of the parenting environment

Among adolescents, many parenting practices have been associated with the initiation and development of drinking behaviors. However, recent studies suggest discrepancies in parents' and adolescents' perceptions of parenting and their links with adolescent use. In this study, we derive two independent sets of underlying parenting profiles (based on parent and adolescent reported behaviors at age 11-12 years), which were then examined in relation to adolescents' drinking behaviors at ages 14 and 17(1/2). Results indicated that the two sets of profiles accounted for little shared variance, with those based on adolescents' reports being stronger predictors of adolescent drinking. Moreover, comparisons of drinking levels across profiles pointed to multiple parenting strategies that may effectively reduce adolescent alcohol experimentation, including simply sustaining a moderate level of awareness of adolescents' whereabouts and activities and avoiding excessive conflict and strictness.

Investigation of genetically mediated child effects on maltreatment

Theory and empirical evidence suggest that children's genetically influenced characteristics help to shape the environments they experience, including the parenting they 'receive'. The extent of these genetically-mediated child effects on childhood maltreatment is not well known. The present study estimates the magnitude of genetically mediated child effects on maltreatment in 3,297 twins and siblings who were part of a large nationally representative sample of adolescents (ADD health). Participants in early adulthood retrospectively reported their experiences of physical and sexual maltreatment and neglect. Results are consistent with small genetically-mediated child effects on physical maltreatment and neglect, and none on sexual maltreatment, and all three forms of maltreatment are influenced mainly by idiosyncratic individual circumstances.

Genotype–environment correlations: implications for determining the relationship between environmental exposures and psychiatric illness

Psychosocial risk factors for psychiatric illness are moderately heritable. This has two implications: first, that individuals actively shape their environments through heritable behaviour; second, that the relationship between environmental exposure and psychopathology may be confounded by genotype. We define three types of genotype-environment correlation (passive, evocative, and active), describe the evidence from quantitative and molecular genetic studies for their existence, and discuss the implications of genotype-environment correlations for the prevention and treatment of psychiatric disorder. Research designs are needed that can test which exposures have truly causal effects on mental illness and which are confounded by genotype, so that clinicians can make informed decisions about when modifying exposures will be likely to result in reductions in mental illness. By considering bi-directional and reciprocal relations between risk exposures and patients' behaviour, clinicians may develop a fuller picture of the causes of disorder and develop more effective treatment methods.

Testing different types of genotype-environment correlation: an extended children-of-twins model

This study presents an extended children-of-twins model, which allowed the authors to test the direction of the association between parenting and child adjustment. Three mechanisms were examined: direct phenotypic influence of parenting on child behavior (controlling for both parental and child genotype), passive genotype-environment correlation, and evocative genotype-environment correlation. This model was tested with Monte Carlo simulations. The authors generated data sets consisting of 1,000 twin parent pairs together with their children and 1,000 twin children pairs together with their parents. These simulated data sets were then used to estimate the model, and the procedure was repeated 1,000 times. The simulation results showed that this model recovered the true values of parameters with high precision. The model was also applied to an observed data set to analyze, as a first example, the association between maternal emotional overinvolvement and child internalizing problems. The results showed that this association was best explained by evocative genotype-environment correlation.

Parental punitive discipline, negative life events and gene-environment interplay in the development of externalizing behavior

BACKGROUND

To investigate the extent to which three putative 'environmental' risk factors, maternal punitive discipline (MPD), paternal punitive discipline (PPD) and negative life events (NLEs), share genetic influences with, and moderate the heritability of, externalizing behavior.

METHOD

The sample consisted of 2647 participants, aged 12-19 years, from the G1219 and G1219Twins longitudinal studies. Externalizing behavior was measured using the Youth Self-Report, MPD, PPD and exposure to NLEs were assessed using the Negative Sanctions Scale and the Life Event Scale for Adolescents respectively.

RESULT

Genetic influences overlapped for externalizing behavior and each 'environmental' risk, indicating gene-environment correlation. When controlling for the gene-environment correlation, genetic variance decreased, and both shared and non-shared environmental influences increased, as a function of MPD. Genetic variance increased as a function of PPD, and for NLEs the only interaction effect was on the level of non-shared environment influence unique to externalizing behavior.

CONCLUSION

The magnitude of the influence of genetic risk on externalizing behavior is contextually dependent, even after controlling for gene-environment correlation.

A longitudinal twin study of the genetic and environmental etiology of maternal hostile-reactive behavior during infancy and toddlerhood

Children's negative characteristics are thought to be a factor in evoking hostile parenting responses. This can result in genotype/environment correlations (rGE) in which children's heritable traits influence the parenting they experience. We did genetic analyses on 292 mothers' self-reported hostile-reactive behaviors toward each of their twins at 5, 18 and 30 months. Finding heritability for a parenting behavior analyzed as a child phenotype is evidence of rGE correlation. The heritability of maternal behavior was modest (29% at 5 months, 0% at 18 months, and 25% at 30 months) and longitudinal analyses indicated that genetic factors at 5 and 30 months were uncorrelated. Common environment factors, probably reflecting characteristics of the mothers, were the main source of variance at the three ages and were highly correlated through time. We concluded that children's heritable characteristics evoked maternal negative response at specific times, but were not responsible for the stability of maternal hostility from infancy to toddlerhood.

Parental monitoring moderates the importance of genetic and environmental influences on adolescent smoking

Although there is a substantial literature on the role of parenting in adolescent substance use, most parenting effects have been small in magnitude and studied outside the context of genetically informative designs, raising debate and controversy about the influence that parents have on their children (D. C. Rowe, 1994). Using a genetically informative twin-family design, the authors studied the role of parental monitoring on adolescent smoking at age 14. Although monitoring had only small main effects, consistent with the literature, there were dramatic moderation effects associated with parental monitoring: At high levels of parental monitoring, environmental influences were predominant in the etiology of adolescent smoking, but at low levels of parental monitoring, genetic influences assumed far greater importance. These analyses demonstrate that the etiology of adolescent smoking varies dramatically as a function of parenting.

Aggression as a mediator of genetic contributions to the association between negative parent-child relationships and adolescent antisocial behavior

Previous research suggests that the association between conflictual parent-child relationships and maladjustment among adolescents is influenced by genetic effects emanating from the adolescents. In this study, we examined whether these effects are mediated by childhood aggression. The data come from the Twin study of CHild and Adolescent Development (TCHAD), a Swedish longitudinal study including 1,314 twin pairs followed from age 13-14 to 16-17. Early adolescent aggression, parental criticism, and delinquency in later adolescence were rated by parents and children at different time points. Multivariate genetic structural equation models were used to estimate genetic and environmental influences on these constructs and on their covariation. The results showed that approximately half of the genetic contribution to the association between parental criticism and delinquency was explained by early adolescent aggression. It suggests that aggression in children evokes negative parenting, which in turn influences adolescent antisocial behavior. The mechanism proposed by these findings is consistent with evocative gene-environment correlation.

Gene-environment interplay and psychopathology: multiple varieties but real effects

Gene-environment interplay is a general term that covers several divergent concepts with different meanings and different implications. In this review, we evaluate research evidence on four varieties of gene-environment interplay. First, we consider epigenetic mechanisms by which environmental influences alter the effects of genes. Second, we focus on variations in heritability according to environmental circumstances. Third, we discuss what is known about gene-environment correlations. Finally, we assess concepts and findings on the interaction between specific identified genes and specific measured environmental risks. In order to provide an understanding of what may be involved in gene-environment interplay, we begin our presentation with a brief historical review of prevailing views about the role of genetic and environmental factors in the causation of mental disorders, and we provide a simplified account of some of the key features of how genes 'work'.

Childhood trauma and personality disorder: toward a biological model

Cross-sectional and prospective associations of personality disorder with childhood trauma provide an important clue regarding the biological mechanism of personality disorder. In this review, empirical literature from several domains is summarized. These include relevant findings from behavioral genetics, preclinical models of early life parental care, and clinical translational studies of personality disorder. Identification of the biological mechanism by which childhood trauma exerts an effect on personality disorder may require modification of the conceptualization of personality disorder, either as a set of categories or dimensions.

Parental discipline and affection and children's prosocial behavior: Genetic and environmental links

The authors investigated genetic and environmental contributions to the relationships between children's (N=9,319 twin pairs) prosocial behavior and parental positivity and negativity toward them. Children's prosocial behavior was rated by parents at ages 3, 4, and 7 and by teachers at age 7. At each age, parents described their feelings and discipline toward each twin. Parental positivity was indexed by positive feelings and positive, non-coercive discipline, and parental negativity was indexed by negative feelings and coercive, punitive discipline. Genetics and the environment both contributed to individual differences in prosocial behavior and in parenting. At all ages, parental positivity correlated positively, and parental negativity correlated negatively with prosocial behavior. Genetic factors largely mediated the negative correlation between prosocial behavior and parental negativity. Shared environmental effects contributed mainly to the positive relationship between prosocial behavior and parental positivity. This pattern was found both cross-sectionally and longitudinally. The findings point to the importance of children's characteristics and of the parent-child relationship in family processes.

The new look of behavioral genetics in developmental psychopathology: gene-environment interplay in antisocial behaviors

This article reviews behavioral-genetic research to show how it can help address questions of causation in developmental psychopathology. The article focuses on studies of antisocial behavior, because these have been leading the way in investigating environmental as well as genetic influences on psychopathology. First, the article illustrates how behavioral-genetic methods are being newly applied to detect the best candidates for genuine environmental causes among the many risk factors for antisocial behavior. Second, the article examines findings of interaction between genes and environments (G x E) associated with antisocial behavior, outlining steps for testing hypotheses of measured G x E. Third, the article envisages future work on gene-environment interplay, arguing that it is an interesting and profitable way forward for psychopathology research.

Personality development: stability and change

In this review, we evaluate four topics in the study of personality development where discernible progress has been made since 1995 (the last time the area of personality development was reviewed in this series). We (a) evaluate research about the structure of personality in childhood and in adulthood, with special attention to possible developmental changes in the lower-order components of broad traits; (b) summarize new directions in behavioral genetic studies of personality; (c) synthesize evidence from longitudinal studies to pinpoint where and when in the life course personality change is most likely to occur; and (d) document which personality traits influence social relationships, status attainment, and health, and the mechanisms by which these personality effects come about. In each of these four areas, we note gaps and identify priorities for further research.

Behavioral genetics of personality

Behavioral genetic personality research has moved from findings of genetic and environmental effects to new areas. Personality disorders have been included, children and adolescents studied, gender effects evaluated, and the importance of rater sources investigated. Recently, multivariate methods have been applied to disentangle the genetic and environmental latent structure, and investigate covariance in mental disorders. Perhaps the most exciting recent developments are the investigations of situation variables, the studies of how genotypes influence how individuals select themselves into situations and other form of gene-environment correlations, and how genotype moderates the effect of situations and circumstances on behavior (gene-environment interaction). In the future, we will learn how personality, partly determined by heredity, influences our entire lives. We will better understand what we experience, how we interpret the experiences and how to react to them effectively. We will learn how our mental lives develop while we interact with the environment, and we will broaden our understanding of which genes are coding for mental health and mental disorders.

The limits of child effects: evidence for genetically mediated child effects on corporal punishment but not on physical maltreatment

Research on child effects has demonstrated that children's difficult and coercive behavior provokes harsh discipline from adults. Using a genetically sensitive design, the authors tested the limits of child effects on adult behavior that ranged from the normative (corporal punishment) to the nonnormative (physical maltreatment). The sample was a 1994-1995 nationally representative birth cohort of 1,116 twins and their families who participated in the Environmental Risk Longitudinal Study. Results showed that environmental factors accounted for most of the variation in corporal punishment and physical maltreatment. However, corporal punishment was genetically mediated in part, and the genetic factors that influenced corporal punishment were largely the same as those that influenced children's antisocial behavior, suggesting a child effect. The authors conclude that risk factors for maltreatment are less likely to reside within the child and more likely to reside in characteristics that differ between families.

The role of the children of twins design in elucidating causal relations between parent characteristics and child outcomes

BACKGROUND

Determination of causal connections between parental measures and child outcomes using typical samples is limited by the inability to account for all confounds, both environmental and genetic. This paper discusses the strength of the Children of Twins (COT) design to highlight the role of specific environments.

METHODS

A new analytical model is presented which helps differentiate and quantify the environmental and genetic processes underlying associations between family-level risk factors and child adjustment. In order to illustrate the COT design, the relation between smoking during pregnancy and child birth weight (BW) is examined in a sample of female twins and their children from Norway and the United States.

RESULTS

The results illustrate that smoking during pregnancy is influenced by genetic factors. However, the Children of Twins model supports the claim that smoking during pregnancy has a direct environmental influence on BW and that genetic and shared environmental confounds cannot account for the association.

CONCLUSIONS

An assessment of the strengths and limitations of the Children of Twins design and a comparison with other research strategies suggest that the design plays a unique role in the study of developmental psychology and psychopathology. Finally, the authors describe how methodological advances and future applications of the design will provide additional insight into the causal processes underlying children's adjustment to environmental stimuli.