Intergenerational transmission of risk for social inhibition: the interplay between parental responsiveness and genetic influences

A Systematic Review and Meta-analysis: Paternal Anxiety and the Emotional and Behavioral Outcomes in Their Offspring

OBJECTIVE

Anxiety disorders are highly prevalent worldwide; however, the literature lacks a meta-analytic quantification of the risk posed by fathers' anxiety for offspring development. This systematic review and meta-analysis aimed to provide a comprehensive estimate of the magnitude of the association between paternal anxiety and emotional and behavioral problems of offspring.

METHOD

In February 2022, Web of Science, Ovid (Embase, MEDLINE, PsycINFO), Trip Database, and ProQuest were searched to identify all quantitative studies that measured anxiety in fathers and emotional and/or behavioral outcomes in offspring. No limits were set for offspring age, publication language, or publication year. Summary estimates were extracted from the primary studies. Meta-analytic random-effects 3-level models were used to calculate correlation coefficients. Quality was assessed using the Newcastle-Ottawa Scale. The study protocol was preregistered with PROSPERO (CRD42022311501) and adhered to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) reporting guidelines.

RESULTS

Of 11,746 records identified, 98 were included in the meta-analysis. Small but significant associations were found between paternal anxiety and offspring emotional and behavioral problems overall (r = 0.16, 95% CI [0.13, 0.19]) and behavioral (r = 0.19, 95% CI [0.13, 0.24]), emotional (r = 0.15, 95% CI [0.12, 0.18]), anxiety (r = 0.13, 95% CI [0.11, 0.16]), and depression (r = 0.13, 95% CI [0.03, 0.23]) problems. Some significant moderators were identified.

CONCLUSION

Paternal mental health is associated with offspring development, and the offspring of fathers with anxiety symptoms or disorders are at increased risk of negative emotional and behavioral outcomes, in line with the principles of multifinality and pleiotropy. The substantial heterogeneity among studies and the overrepresentation of White European American groups in this literature highlight the need for further research.

DIVERSITY & INCLUSION STATEMENT

While citing references scientifically relevant for this work, we also actively worked to promote inclusion of historically underrepresented racial and/or ethnic groups in science in our reference list.

Examination of promotive and protective effects on early adolescent prosocial behavior through a bioecological lens

Introduction

Prosocial behavior during childhood has been associated with numerous positive developmental and behavioral outcomes in adolescence and adulthood. Prosocial behavior, which includes cooperation and helping others, develops within a bioecological context. Considering it through such a lens enhances the understanding of the roles of different bioecological factors in its development.

Methods

Using data from a longitudinal study of adopted children and children reared with their biological parents, this paper examined if positive aspects of a child's bioecological system at age 7 predict prosocial behavior in early adolescence (age 11), and whether these bioecological factors could offset risk due to biological family psychopathology and/or maternal prenatal substance use. The analyses incorporated variables from different levels of Bronfenbrenner's bioecological model (the individual, microsystem, exosystem, and macrosystem) and examined the promotive, and potentially protective, effect of each contextual factor, while also considering their interplay with biological family psychopathology and prenatal substance use.

Results

Results from linear regression models indicated that the microsystem variable of parental warmth at age 7 had a promotive effect on age 11 prosocial behavior. Further, in addition to its main effect, parental warmth was protective against maternal substance use during pregnancy when children were raised with their biological parent (s). Household type (biological family) and biological family internalizing psychopathology were the only other significant predictors in the model, with each associated with lower prosocial behavior at age 11.

Discussion

Study results extend prior work on the benefits of parental warmth on child outcomes by employing a strength-based, bioecological approach to the development of prosocial behavior during early adolescence and examining "for whom" the effects of parental warmth are most protective.

Sex-Specific Transmission of Anxiety Disorders From Parents to Offspring

IMPORTANCE

Although anxiety disorders are known to run in families, the relative contribution of genes and environment is unclear. Patterns of sex-specific transmission of anxiety may point to different pathways in how parents pass anxiety disorders down to their children; however, the association of parent and offspring sex with the transmission of anxiety disorders has not been previously studied.

OBJECTIVE

To examine whether the transmission of anxiety from parents to children is sex specific.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional family study recruited participants from the general population (enriched for familial risk of mood disorders) in Nova Scotia, Canada, from February 1, 2013, to January 31, 2020.

EXPOSURES

Anxiety disorder in the same-sex or opposite-sex parent.

MAIN OUTCOMES AND MEASURES

Semistructured interviews were used to establish lifetime diagnoses of anxiety disorder in parents and offspring. The association between anxiety disorder in the same-sex or opposite-sex parent and anxiety disorders in the offspring was tested with logistic regression.

RESULTS

A total of 398 offspring (203 female offspring with a mean [SD] age of 11.1 [3.7] years and 195 male offspring with a mean [SD] age of 10.6 [3.1] years) of 221 mothers and 237 fathers participated in the study. Anxiety disorders in the same-sex parent (odds ratio [OR], 2.85; 95% CI, 1.52-5.34; P = .001) were associated with increased rates of anxiety disorders in the offspring, whereas anxiety disorders in the opposite-sex parent (OR, 1.51; 95% CI, 0.81-2.81; P = .20) were not. Sharing a household with a same-sex parent without anxiety was associated with lower rates of offspring anxiety (OR, 0.38; 95% CI, 0.22-0.67; P = .001), but the presence of an opposite-sex parent without anxiety was not (OR, 0.96; 95% CI, 0.56-1.63; P = .88).

CONCLUSIONS AND RELEVANCE

In this cross-sectional study of families, an association between the same-sex parent's anxiety disorder and anxiety disorders in offspring suggests an environmental mechanism, such as modeling. Future studies should establish whether treating parents' anxiety may protect their children from developing an anxiety disorder.

Parenting in the Context of the Child: Genetic and Social Processes

The focus on the role of parenting in child development has a long-standing history. When measures of parenting precede changes in child development, researchers typically infer a causal role of parenting practices and attitudes on child development. However, this research is usually conducted with parents raising their own biological offspring. Such research designs cannot account for the effects of genes that are common to parents and children, nor for genetically influenced traits in children that influence how they are parented and how parenting affects them. The aim of this monograph is to provide a clearer view of parenting by synthesizing findings from the Early Growth and Development Study (EGDS). EGDS is a longitudinal study of adopted children, their birth parents, and their rearing parents studied across infancy and childhood. Families (N = 561) were recruited in the United States through adoption agencies between 2000 and 2010. Data collection began when adoptees were 9 months old (males = 57.2%; White 54.5%, Black 13.2%, Hispanic/Latinx 13.4%, Multiracial 17.8%, other 1.1%). The median child age at adoption placement was 2 days (M = 5.58, SD = 11.32). Adoptive parents were predominantly in their 30s, White, and coming from upper-middle- or upper-class backgrounds with high educational attainment (a mode at 4-year college or graduate degree). Most adoptive parents were heterosexual couples, and were married at the beginning of the project. The birth parent sample was more racially and ethnically diverse, but the majority (70%) were White. At the beginning of the study, most birth mothers and fathers were in their 20s, with a mode of educational attainment at high school degree, and few of them were married. We have been following these family members over time, assessing their genetic influences, prenatal environment, rearing environment, and child development. Controlling for effects of genes common to parents and children, we confirmed some previously reported associations between parenting, parent psychopathology, and marital adjustment in relation to child problematic and prosocial behavior. We also observed effects of children's heritable characteristics, characteristics thought to be transmitted from parent to child by genetic means, on their parents and how those effects contributed to subsequent child development. For example, we found that genetically influenced child impulsivity and social withdrawal both elicited harsh parenting, whereas a genetically influenced sunny disposition elicited parental warmth. We found numerous instances of children's genetically influenced characteristics that enhanced positive parental influences on child development or that protected them from harsh parenting. Integrating our findings, we propose a new, genetically informed process model of parenting. We posit that parents implicitly or explicitly detect genetically influenced liabilities and assets in their children. We also suggest future research into factors such as marital adjustment, that favor parents responding with appropriate protection or enhancement. Our findings illustrate a productive use of genetic information in prevention research: helping parents respond effectively to a profile of child strengths and challenges rather than using genetic information simply to identify some children unresponsive to current preventive interventions.

Maternal and paternal influences on childhood anxiety symptoms: A genetically sensitive comparison

This study tested the theory that anxious fathers pose a quantitatively different environmental influence on childhood anxiety than anxious mothers. The analysed sample contained 502 linked adoption units from the Early Growth and Development Study (EGDS), a longitudinal multisite study that follows 561 adopted children (57.2% boys) and their adoptive and birth parents, who were recruited through US adoption agencies. A Bayesian latent growth model predicted child anxiety symptoms between 18 months and 4.5 years from inherited (birth parent anxiety) and rearing parent anxiety. This model revealed little evidence for a difference in the influence of maternal and paternal rearing parent anxiety on child anxiety symptoms. Contrary to theoretical predictions, anxiety in the rearing father is likely to have an equivalent influence to that of the mother on both child anxiety symptoms at 18 months old and their developmental trajectory over the preschool years.

The Early Growth and Development Study: A Dual-Family Adoption Study from Birth Through Adolescence

The Early Growth and Development Study (EGDS) is a prospective adoption study of birth parents, adoptive parents and adopted children (n = 561 adoptees). The original sample has been expanded to include siblings of the EGDS adoptees who were reared by the birth mother and assessed beginning at age 7 years (n = 217 biological children), and additional siblings in both the birth and adoptive family homes, recruited when the adoptees were 8-15 years old (n = 823). The overall study aims are to examine how family, peer and contextual processes affect child and adolescent adjustment, and to examine their interplay (mediation, moderation) with genetic influences. Adoptive and birth parents were originally recruited through adoption agencies located throughout the USA following the birth of a child. Assessments are ongoing and occurred in 9 month's intervals until the adoptees turned 3 years of age, and in 1 to 2 year intervals thereafter through age 15. Data collection includes the following primary constructs: child temperament, behavior problems, mental health, peer relations, executive functioning, school performance and health; birth and adoptive parent personality characteristics, mental health, health, context, substance use, parenting and marital relations; and the prenatal environment. Findings highlight the power of the adoption design to detect environmental influences on child development and provide evidence of complex interactions and correlations between genetic, prenatal environmental and postnatal environmental influences on a range of child outcomes. The study sample, procedures and an overview of findings are summarized and ongoing assessment activities are described.

The children of preterm survivors: shyness, parenting, and parental stress

Extremely low birth weight (ELBW) survivors have higher rates of shyness, a risk factor for poorer outcomes across the life span. Due to advances in fetal and neonatal medicine, the first generation of ELBW survivors have survived to adulthood and become parents. However, no studies have investigated the transmission of their stress vulnerability to their offspring. We explored this phenomenon using a population-based cohort of ELBW survivors and normal birth weight (NBW) controls. Using data from three generations, we examined whether the shyness and parenting stress of ELBW and NBW participants (Generation 2) mediated the relation between the parenting style of their parents (Generation 1) and shyness in their offspring (Generation 3), and the extent to which exposure to perinatal adversity (Generation 2) moderated this mediating effect. We found that among ELBW survivors, parenting stress (in Generation 2) mediated the relation between overprotective parenting style in Generation 1 (grandparents) and child shyness in Generation 3. These findings suggest that perinatal adversity and stress may be transmitted to the next generation in humans, as reflected in their perceptions of their children as shy and socially anxious, a personality phenotype that may subsequently place their children at risk of later mental and physical health problems.

Effects of Gestational Age and Early Parenting on Children's Social Inhibition at 6 Years

Preterm birth (<37 weeks' gestation) has been associated with problems in social functioning. Whether social inhibition is specifically related to preterm birth and whether early parenting may protect against social inhibition difficulties is unknown. To explore effects of gestational age and early parent-infant relationships on social inhibition, 1314 children born at 26-41 weeks gestational age were studied as part of the prospective Bavarian Longitudinal Study. Early parent-infant relationship quality was assessed postnatally with the parent-infant relationship index. Social inhibition was assessed at age 6 years using an experimental procedure, in which nonverbal and verbal responses were coded into social inhibition categories (disinhibited, normally responsive, inhibited). Multinomial logistic regressions indicated that children with lower gestational age showed more socially disinhibited (nonverbal: OR = 1.27 [95% CI = 1.17-1.40], verbal: OR = 1.23 [95% CI 1.13-1.35]) and inhibited (nonverbal: OR = 1.21 [95% CI = 1.11-1.32], verbal: OR = 1.11 [95% CI = 1.01-1.21]) responses. Good early parent-infant relationships were associated with less verbal disinhibition (OR = 0.70 [95% CI = 0.52-0.93]). Findings suggest that children with lower gestational age are at greater risk to be both socially inhibited and disinhibited. Early parenting affected risk of abnormal social responses. Supporting early parent-infant relationships may reduce preterm children's risk for social difficulties.

Anger as a Basic Emotion and Its Role in Personality Building and Pathological Growth: The Neuroscientific, Developmental and Clinical Perspectives

Anger is probably one of the mostly debated basic emotions, owing to difficulties in detecting its appearance during development, its functional and affective meaning (is it a positive or a negative emotion?), especially in human beings. Behaviors accompanied by anger and rage serve many different purposes and the nuances of aggressive behaviors are often defined by the symbolic and cultural framework and social contexts. Nonetheless, recent advances in neuroscientific and developmental research, as well as clinical psychodynamic investigation, afford a new view on the role of anger in informing and guiding many aspects of human conducts. Developmental studies have confirmed the psychophysiological, cognitive and social acquisition that hesitate in the pre-determined sequence appearance of anger and rage in the first 2 years of life. The so-called affective neurosciences have shown the phylogenetic origin of the two circuits underlying the emergence of anger along with its evolutionary role for promoting survival. This view has been integrated by the psychodynamic theory of motivational systems that attribute a double role to anger: on the one hand, this affect works as an inwardly directed signal concerning a pressure to overcome an obstacle or an aversive situation; on the other hand, anger is also an outwardly directed communicative signal establishing differentiation and conflict within interpersonal relationships and affective bonds. Of course, human peculiar mental functioning requires the appraisal of such signals by higher cortical functions and, there is little doubt that the meaning that orientates individual behaviors is, eventually, construed on a social and cultural level. At the same time, everyday life experiences as well as clinical insights into psychopathic, narcissistic and borderline personality pathology clearly illustrate the necessity to correctly interpret and give answers to the basic questions raised around the topic of anger as a basic emotion.

The serotonin transporter promoter polymorphism moderates the continuity of behavioral inhibition in early childhood

Persistently elevated behavioral inhibition (BI) in children is a marker of vulnerability to psychopathology. However, little research has considered the joint influences of caregiver and child factors that may moderate the continuity of BI in early childhood, particularly genetic variants that may serve as markers of biological plasticity, such as the serotonin transporter linked polymorphic region (5-HTTLPR). We explored this issue in 371 preschoolers and their caregivers, examining whether parent characteristics (i.e., overinvolvement or anxiety disorder) and child 5-HTTLPR influenced the continuity of BI between ages 3 and 5. Measures were observational ratings of child BI, observational and questionnaire measures of parenting, and parent interviews for anxiety disorder history, and children were genotyped for the 5-HTTLPR. Parent factors did not moderate the association between age 3 and age 5 BI; however, child BI at age 3 interacted with children's 5-HTTLPR variants to predict age 5 BI, such that children with at least one copy of the short allele exhibited less continuity of BI over time relative to children without this putative plasticity variant. Findings are consistent with previous work indicating the 5-HTTLPR short variant increases plasticity to contextual influences, thereby serving to decrease the continuity of BI in early childhood.

Development of self-inflicted injury: Comorbidities and continuities with borderline and antisocial personality traits

Self-inflicted injury (SII) is a continuum of intentionally self-destructive behaviors, including nonsuicidal self-injuries, suicide attempts, and death by suicide. These behaviors are among the most pressing yet perplexing clinical problems, affecting males and females of every race, ethnicity, culture, socioeconomic status, and nearly every age. The complexity of these behaviors has spurred an immense literature documenting risk and vulnerability factors ranging from individual to societal levels of analysis. However, there have been relatively few attempts to articulate a life span developmental model that integrates ontogenenic processes across these diverse systems. The objective of this review is to outline such a model with a focus on how observed patterns of comorbidity and continuity can inform developmental theories, early prevention efforts, and intervention across traditional diagnostic boundaries. Specifically, when SII is viewed through the developmental psychopathology lens, it becomes apparent that early temperamental risk factors are associated with risk for SII and a range of highly comorbid conditions, such as borderline and antisocial personality disorders. Prevention efforts focused on early-emerging biological and temperamental contributors to psychopathology have great potential to reduce risk for many presumably distinct clinical problems. Such work requires identification of early biological vulnerabilities, behaviorally conditioned social mechanisms, as well as societal inequities that contribute to self-injury and underlie intergenerational transmission of risk.

Shared genetic influences among childhood shyness, social competences, and cortical responses to emotions

Visual event-related potentials (ERPs) evoked by facial expressions are useful to map socioemotional responses among shy children and to predict transition into social phobia. We investigated the sources of covariation among childhood shyness, social competences, and ERPs to other children's happy, neutral, and angry expressions. Electrophysiological and twin analyses examined the phenotypic and etiological association among an index of childhood shyness, an index of social competences, and ERP responses to facial expressions in 200 twins (mean age=9.23years). Multivariate twin analyses showed that the covariation among shyness, social competences, and a composite of a frontal late negative component occurring around 200-400ms in response to happy, neutral, and angry expressions could be entirely explained by shared genetic factors. A coherent causal structure links childhood shyness, social competences, and the cortical responses to facial emotions. A common genetic substrate can explain the interrelatedness of individual differences for childhood shyness, social competences, and some associated electrophysiological responses to socioemotional signals.

Early inherited risk for anxiety moderates the association between fathers' child-centered parenting and early social inhibition

Studies of the role of the early environment in shaping children's risk for anxiety problems have produced mixed results. It is possible that inconsistencies in previous findings result from a lack of consideration of a putative role for inherited influences moderators on the impact of early experiences. Early inherited influences not only contribute to vulnerabilities for anxiety problems throughout the lifespan, but can also modulate the ways that the early environment impacts child outcomes. In the current study, we tested the effects of child-centered parenting behaviors on putative anxiety risk in young children who differed in levels of inherited vulnerability. We tested this using a parent-offspring adoption design and a sample in which risk for anxiety problems and parenting behaviors were assessed in both mothers and fathers. Inherited influences on anxiety problems were assessed as anxiety symptoms in biological parents. Child-centered parenting was observed in adoptive mothers and fathers when children were 9 months old. Social inhibition, an early temperament marker of anxiety risk, was observed at child ages 9 and 18 months. Inherited influences on anxiety problems moderated the link between paternal child-centered parenting during infancy and social inhibition in toddlerhood. For children whose birth parents reported high levels of anxiety symptoms, greater child-centered parenting in adoptive fathers was related to greater social inhibition 9 months later. For children whose birth parents reported low levels of anxiety symptoms, greater child-centered parenting in adoptive fathers was related to less social inhibition across the same period.

A review of 25 years of research in bidirectionality in parent–child relationships

The concept of bidirectionality represents a process of mutual influence between parent and child, whereby each influences the other as well as the dyadic relationship. Despite the widespread acceptance of bidirectional models of influence, there is still a lack of integration of such models in current research designs. Research on bidirectionality could be strengthened through the adoption of advanced methodologies, including behavioral-genetic research designs and advanced structural equation modeling. The aim of this empirical review is to further advance the study of bidirectionality by evaluating the evidence from 25 years of bidirectionality research in infancy and early childhood. The review indicates significant advancements in the use of methods that address the ecological validity of bidirectional effects, as well as areas that continue to rely on correlational designs to detect bidirectional effects. We describe analytic approaches that may improve the specificity of bidirectionality evidence and highlight gene–environment interaction designs as a promising area for future bidirectionality research.

Associations Between Infant Negative Affect and Parent Anxiety Symptoms are Bidirectional: Evidence from Mothers and Fathers

Little is known about child-based effects on parents' anxiety symptoms early in life despite the possibility that child characteristics may contribute to the quality of the early environment and children's own long-term risk for psychological disorder. We examined bidirectional effects between parent anxiety symptoms and infant negative affect using a prospective adoption design. Infant negative affect and adoptive parent anxiety symptoms were assessed at child ages 9, 18, and 27 months. Birth parent negative affect was assessed at child age 18 months. More anxiety symptoms in adoptive parents at child age 9 months predicted more negative affect in infants 9 months later. More infant negative affect at child age 9 months predicted more anxiety symptoms in adoptive parents 18 months later. Patterns of results did not differ for adoptive mothers and adoptive fathers. Birth parent negative affect was unrelated to infant or adoptive parent measures. Consistent with expectations, associations between infant negative affect and rearing parents' anxiety symptoms appear to be bidirectional. In addition to traditional parent-to-child effects, our results suggest that infants' characteristics may contribute to parent qualities that are known to impact childhood outcomes.

Cognitive and language performance in children is associated with maternal social anxiety disorder: A study of young mothers in southern Brazil

BACKGROUND

It has been shown that maternal mental health is associated with poorer skills development in the offspring. However, the evidence evaluating the association between social anxiety disorder (SAD) and cognitive or language development, is scarce.

AIM

To evaluate the association between maternal SAD and performance in cognitive and language tests in 30-month old children.

STUDY DESIGN

This was a cohort study involving young women evaluated since pregnancy.

SUBJECTS

We evaluated 520 mother-child dyads who received prenatal medical assistance through the National Public Health System in a southern Brazilian city, from October 2009 to March 2011.

OUTCOME MEASURES

We used the Mini Neuropsychiatric Interview Plus (MINI Plus) to assess SAD among young mothers. Cognitive and language performance in their offspring was analyzed using the Bayley Scales of Infant and Toddler Development - 3rd Edition.

RESULTS

We found an association between maternal SAD and performance in cognitive and language tests. Children of mothers with SAD had in average 4.5 less points in the Bayley scale, when compared to those with mothers without SAD: in the cognitive (β=-4.53 [95% CI -7.8; -1.1] p=0.008) and language subscales (β=-4.54 [95% CI -9.0; -0.5] p=0.047).

CONCLUSIONS

Our findings suggest that children with mothers suffering from SAD have poorer cognitive abilities and language skills.

Birth and adoptive parent anxiety symptoms moderate the link between infant attention control and internalizing problems in toddlerhood

Attention control plays an important role in the development of internalizing symptoms in children. We explored the degree to which infants' genetic and environmentally based risk moderated the link between attention control and internalizing problems during toddlerhood. These associations were examined within a prospective adoption design, enabling the disentanglement of genetic and environmental risk for internalizing problems. Attention control in adopted infants was observed during periods of distress at age 9 months. Birth parents' anxiety symptoms were used as an index of genetic risk, while adoptive parents' anxiety symptoms were used as an index of environmental risk. Adoptive mothers and fathers reported on children's internalizing problems when children were 18 and 27 months old. Greater attention control in infancy appeared to mitigate genetically based risk for internalizing problems during toddlerhood when children were raised by adoptive parents who were low in anxiety. Findings suggest that for genetically susceptible children who are raised in low-risk environments, attention control may provide a protective factor against developing internalizing problems across early life.

Transactions between child social wariness and observed structured parenting: evidence from a prospective adoption study

This investigation examined the mutual influences between structured parenting and child social wariness during toddlerhood using a longitudinal adoption design. The sample consisted of 361 adoption-linked families, each including an adopted child, adoptive parents, and a birth mother. Heightened social wariness in children at age 18 months predicted reduced levels of observed structured parenting (i.e., less directive parenting with fewer commands and requests) in adoptive mothers at age 27 months. Adoptive fathers' lower structured parenting at age 18 months predicted subsequent elevation in child social wariness. Birth mothers' history of fear-related anxiety disorders was not associated with child social wariness. Findings highlight the role of dynamic family transactions in the development of social wariness during toddlerhood.

The Early Growth and Development Study: a prospective adoption study from birth through middle childhood

The Early Growth and Development Study is a prospective adoption study of birth parents, adoptive parents, and adopted children recruited in two cohorts (N = 561 triads). The primary study aims are to examine how family, peer, and contextual processes affect children's adjustment, and to examine their interplay (mediation, moderation) with genetic influences. Participants were recruited through adoption agencies located throughout the United States following the birth of a child. Assessments are ongoing, in 9-month intervals until the child reaches 3 years of age and in 1-year intervals thereafter through age 9. Data collection includes the following primary constructs: child temperament, social behavior, school performance, mental health, and health; birth and adoptive parent personality characteristics, mental health, competence, stress, health, context, substance use, parenting, and marital relations; and pregnancy use of drugs and maternal stress during pregnancy. DNA and salivary cortisol samples have also been collected. Analyses have indicated evidence for genotype-environment interactions during early childhood. Study procedures, sample representativeness (including tests of potential confounds in the adoption design), and an overview of findings to date are summarized, and future plans are described.