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

Disentangling genetic and environmental influences on early language development: The interplay of genetic propensity for negative emotionality and surgency, and parenting behavior effects on early language skills in an adoption study

Parenting and children's temperament are important influences on language development. However, temperament may reflect prior parenting, and parenting effects may reflect genes common to parents and children. In 561 U.S. adoptees (57% male) and their birth and rearing parents (70% and 92% White, 13% and 4% African American, and 7% and 2% Latinx, respectively), this study demonstrated how genetic propensity for temperament affects language development, and how this relates to parenting. Genetic propensity for negative emotionality inversely predicted language at 27 months (β = -.15) and evoked greater maternal warmth (β = .12), whereas propensity for surgency positively predicted language at 4.5 years (β = .20), especially when warmth was low. Parental warmth (β = .15) and sensitivity (β = .19) further contributed to language development, controlling for common gene effects.

The Detection of Environmental Influences on Academic Achievement Appears to Depend on the Analytic Approach

One long-standing analytic approach in adoption studies is to examine correlations between features of adoptive homes and outcomes of adopted children (hereafter termed 'measured environment correlations') to illuminate environmental influences on those associations. Although results from such studies have almost uniformly suggested modest environmental influences on adopted children's academic achievement, other work has indicated that adopted children's achievement is routinely higher than that of their reared-apart family members, often substantially so. We sought to understand this discrepancy. We examined academic achievement and literacy-promotive features of the home in 424 yoked adoptive/biological families participating in the Early Growth and Development Study (EGDS; i.e., adopted children, adoptive mothers, birth mothers, and biological siblings of the adopted children remaining in the birth homes) using an exhaustive modeling approach. Results indicated that, as anticipated, adopted children scored up to a full standard deviation higher on standardized achievement tests relative to their birth mothers and reared-apart biological siblings. Moreover, these achievement differences were associated with differences in the literacy-promotive features of the adoptive and birth family homes, despite minimal measured environment correlations within adoptive families. A subsequent simulation study highlighted noise in measured environmental variables as an explanation for the decreased utility of measured environment correlations. We conclude that the field's heavy focus on measured environment correlations within adoptive families may have obscured detection of specific environmental effects on youth outcomes, and that future adoption studies should supplement their measured environment analyses with mean differences between reared-apart relatives.

Influence of early childhood parental hostility and socioeconomic stress on children's internalizing symptom trajectories from childhood to adolescence

Introduction

Children and adolescents with elevated internalizing symptoms are at increased risk for depression, anxiety, and other psychopathology later in life. The present study examined the predictive links between two bioecological factors in early childhood-parental hostility and socioeconomic stress-and children's internalizing symptom class outcomes, while considering the effects of child sex assigned at birth on internalizing symptom development from childhood to adolescence.

Materials and Methods

The study used a sample of 1,534 children to test the predictive effects of socioeconomic stress at ages 18 and 27 months; hostile parenting measured at child ages 4-5; and sex assigned at birth on children's internalizing symptom latent class outcomes at child ages 7-9, 10-12, 13-15, and 16-19. Analyses also tested the mediating effect of parenting on the relationship between socioeconomic stress and children's symptom classes. Other covariates included parent depressive symptoms at child ages 4-5 and child race and ethnicity.

Results

Analyses identified three distinct heterogenous internalizing symptom classes characterized by relative symptom levels and progression: low (35%); moderate and increasing (41%); and higher and increasing (24%). As anticipated, higher levels of parental hostility in early childhood predicted membership in the higher and increasing symptom class, compared with the low symptom class (odds ratio (OR) = .61, 95% confidence interval (CI) [.48,.77]). Higher levels of early childhood socioeconomic stress were also associated with the likelihood of belonging to the higher-increasing symptom class compared to the low and moderate-increasing classes (OR = .46, 95% CI [.35,.60] and OR = .56, 95% CI [.44,.72], respectively). The total (c = .61) and direct (c' = .57) effects of socioeconomic stress on children's symptom class membership in the mediation analysis were significant (p <.001).

Discussion

Study findings suggest that intervening on modifiable bioecological stressors-including parenting behaviors and socioeconomic stressors-may provide important protective influences on children's internalizing symptom trajectories.

Unique influences of pregnancy and anticipated parenting on cigarette smoking: results and implications of a within-person, between-pregnancy study

Not all pregnant individuals want to become parents and "parenting intention" can also vary within individuals during different pregnancies. Nevertheless, the potential impact of parenting intention on health-related behavior during pregnancy has been heavily underexplored. In this study, we employed a within-person between pregnancy design to estimate the effect of parenting-specific influences on smoking, separate from pregnancy-specific and individual-level influences. We quantified within-mother differences in smoking during pregnancies of infants they reared (n = 84) versus pregnancies of infants they placed for adoption at birth (n = 65) using multivariate mixed-effects Poisson regression models. Mean cigarettes/day declined as the pregnancy progressed regardless of whether infants were reared or placed. However, participants smoked fewer cigarettes/day during reared pregnancies. Relative to "adopted" pregnancies, smoking during "reared" pregnancies was lower by 24%, 41%, and 54% in first (95% CI 0.64-0.90; p = 0.001), second (95% CI 0.48-0.72; p < 0.001), and third trimesters (95% CI 0.36-0.59; p < 0.001), respectively, independent of between-pregnancy differences in maternal age, fetal sex, parity, and pregnancy complications. Female sex and nulliparity were protective. Parenting intention was associated with a protective effect on pregnancy smoking independent of pregnancy-specific influences and individual characteristics. Failure to consider the impact of parenting intention on health-related behavior during pregnancy could perpetuate an unrealistic expectation to "do what's best for the baby" and stigmatize women with unintended or unwanted pregnancies.

The pernicious role of stress on intergenerational continuity of psychopathology

Development and Psychopathology has been a premier resource for understanding stressful childhood experiences and the intergenerational continuity of psychopathology. Building on that tradition, we examined the unique and joint influences of maternal stress on children's effortful control (age 7) and externalizing behavior (age 11) as transmitted via genetics, the prenatal environment, and the postnatal environment. The sample included N = 561 adopted children and their biological and adoptive parents. Path models identified a direct effect of biological mother life stress on children's effortful control (β = -.08) and an indirect effect of her life stress on child externalizing behavior via effortful control (β = .52), but no main or indirect effects of biological parent psychopathology, prenatal stress, or adoptive mother adverse childhood experiences (ACES). Adoptive mother ACES amplified the association between biological mother life stress and child effortful control (β = -.08), externalizing behavior (β = 1.41), and the indirect effect via effortful control, strengthening associations when adoptive mothers reported average or high ACES during their own childhoods. Results suggest that novel study designs are needed to enhance the understanding of how life stress gets "under the skin" to affect psychopathology in the offspring of adults who have experienced stress.

Mothers' symptoms of anxiety and depression and the development of child temperament: A genetically informative, longitudinal investigation

Background

Child temperament traits and mothers' emotional symptoms relating to anxiety and depression may drive changes in one another, leading to their 'co-development' across time. Alternatively, links between mother and child traits may be attributable to shared genetic propensities. We explored longitudinal associations between mothers' emotional symptoms and child temperament traits and adjusted for genetic effects shared across generations.

Methods

This study is based on the Norwegian Mother, Father and Child Cohort Study (MoBa). Mothers (n = 34,060) reported on their symptoms of anxiety and depression, and temperament among offspring (n = 42,526), at child ages 1.5, 3 and 5 years. Structural equation models parameterised developmental change in traits, and an extended family design adjusted for genetic effects.

Results

We found individual differences in stable trait scores and rate of change for all study variables. Longitudinal stability in mothers' emotional symptoms was associated with longitudinal stability in offspring emotionality (r = 0.143), shyness (r = 0.031), and sociability (r = -0.015). Longitudinal change in mothers' symptoms showed very small or negligible correlations with longitudinal change in child temperament. Both genetic and environmental influences explained the stable longitudinal association between mothers' symptoms and child emotionality.

Conclusions

The studied associations between mother and child traits across time appeared to be due to stable, trait-like factors, involving genetic and environmental influence, rather than their co-development. Findings contribute knowledge on how emotional symptoms develop in families across time, and the methods with which we can explore such development.

Modeling BMI z score lability during childhood as a function of child temperament and genetic risk for obesity

OBJECTIVE

This study aimed to examine whether child genetic risk for obesity and temperament (i.e., negative affectivity, effortful control) accounted for stability versus lability in children's weight status (BMI z score) over time.

METHODS

A total of 561 adopted children (42% female; 56% Caucasian, 13% African American, 11% Latino, and 20% other) and their birth and adoptive parents were followed from birth to age 9 years. The multilevel location-scale model was used to examine whether child genetic risk for obesity and temperament were related to differences in level and lability in child BMI z scores over time.

RESULTS

For the full sample, higher levels of child negative affectivity were associated with greater BMI z score lability, whereas higher levels of effortful control and children's mean-level BMI z scores were related to less lability across childhood. Additional analyses examined associations within groups of children with healthy versus overweight/obesity weight statuses. Within the healthy weight status group only, better effortful control was associated with more stable BMI z scores, whereas genetic risk for higher BMI was associated with more labile BMI z scores.

CONCLUSIONS

These findings provide insights into factors that can be harnessed to redirect unhealthy trajectories as well as factors that may challenge redirection or maintain a healthy trajectory.

Developmental trajectories of behavioral inhibition from infancy to age seven: The role of genetic and environmental risk for psychopathology

The present study leveraged data from a longitudinal adoption study of 361 families recruited between 2003 and 2010 in the United States. We investigated how psychopathology symptoms in birth parents (BP; Mage  = 24.1 years; 50.5-62.9% completed high school) and adoptive parents (AP; Mage  = 37.8 years; 80.9% completed college; 94% mother-father couples) influenced children's behavioral inhibition (BI) trajectories. We used latent growth models of observed BI at 18 and 27 months, and 4.5 and 7 years in a sample of adopted children (Female = 42%, White = 57%, Black = 11%, Multi-racial = 21%, Latinx = 9%). BI generally decreased over time, yet there was substantial variability in these trajectories. Neither BP nor AP psychopathology symptoms independently predicted systematic differences in BI trajectories. Instead, we found that AP internalizing symptoms moderated the effects of BP psychopathology on trajectories of BI, indicating a gene by environment interaction.

Annual Research Review: Towards a deeper understanding of nature and nurture: combining family-based quasi-experimental methods with genomic data

Distinguishing between the effects of nature and nurture constitutes a major research goal for those interested in understanding human development. It is known, for example, that many parent traits predict mental health outcomes in children, but the causal processes underlying such associations are often unclear. Family-based quasi-experimental designs such as sibling comparison, adoption and extended family studies have been used for decades to distinguish the genetic transmission of risk from the environmental effects family members potentially have on one another. Recently, these designs have been combined with genomic data, and this combination is fuelling a range of exciting methodological advances. In this review we explore these advances - highlighting the ways in which they have been applied to date and considering what they are likely to teach us in the coming years about the aetiology and intergenerational transmission of psychopathology.

Joint Consideration of Means and Variances Might Change the Understanding of Etiology

Twin and adoption studies compare the similarities of people with differing degrees of relatedness to estimate genetic and environmental contributions to trait population variance. The analytic workhorse of these kinds of variance-focused designs is the intraclass correlation, which estimates similarity between pairs of individuals. Group means, by contrast, play no overt role in estimating genetic and environmental influences. Although this focus on variance has made very important contributions to understanding psychological characteristics, we contend that the exclusion of mean effects from behavioral genetic designs may have obscured key environmental influences and impeded full appreciation of the ubiquity and nature of gene-environment interplay in human outcomes. We provide empirical examples already in the literature and a theoretical framework for thinking through the incorporation of mean effects using largely forgotten, non-Mendelian theory regarding how genes influence human outcomes. We conclude that the field needs to develop models capable of fully incorporating mean effects into twin and adoption studies.

Family interactions in toddlerhood influence social competence in preschool age: Accounting for genetic and prenatal influences

Identification of early promotive and risk factors for social competence is important for fostering children's successful social development; particularly given social competence is essential for children's later academic and psychological well-being. While research suggests that the early parent-child relationship, genetics, and prenatal influences are associated with social competence, there is less research considering how these factors may operate together to shape children's social competence in early childhood. Using a genetically informed sample from the Early Growth and Development Study (N = 561), we examined multiple levels of influence (i.e., genetic, prenatal, parenting, and child characteristics) on children's social competence at 4.5 years old. Results from structural equation models showed adoptive mother overreactivity at 18 months was positively associated with child dysregulation at 27 months, which, in turn, was associated with lower levels of social competence at 4.5 years. Also, child reactivity at 18 months was independently associated with higher levels of adoptive mother overreactivity at 27 months, which, in turn, was associated with lower levels of social competence at 4.5 years. Finally, we found an evocative effect on adoptive fathers' overreactivity at 18 months such that prenatal birth mother distress was negatively associated with adoptive fathers' overreactivity at 18 months. Overall, this study found evidence for genetic influences, and bidirectional associations between parent and child in toddlerhood that are related to lower levels of social competence when children were 4.5 years old. We also found that the prenatal environment was associated with parenting, but not with child behavior directly. This study's ability to simultaneously examine multiple domains of influence helps provide a more comprehensive picture of important mechanisms and developmental periods for children's early social competence.

The Potential of Children's Rearing Environment to Overcome Genetic Propensity for Low Reading Achievement

Genetic studies show that children's reading achievement is in part genetically influenced, and intervention studies show that reading achievement can be increased by environmental interventions. However, correlational and mean-level analytic strategies are rarely integrated into achievement research, potentially leading to misinterpretation of results. The parent-offspring adoption design offers a novel opportunity to examine the independent and joint roles of genetic and rearing environmental contributions. The sample included 344 adopted children in first grade and their biological and adoptive parents. Results indicated that adoptees' reading scores were correlated with their biological parents' scores, but not with their adoptive parents' scores, suggesting genetic influences. In addition, examination of mean scores indicated that adoptees' scores were significantly greater than their biological parents' (p's < .001) for all subtests, suggesting promotive effects of the rearing environment. This pattern was present even when biological parents scored >1 standard deviation below the biological parent mean on achievement.

Using genetic designs to identify likely causal environmental contributions to psychopathology

The multifactorial nature of psychopathology, whereby both genetic and environmental factors contribute risk, has long been established. In this paper, we provide an update on genetically informative designs that are utilized to disentangle genetic and environmental contributions to psychopathology. We provide a brief reminder of quantitative behavioral genetic research designs that have been used to identify potentially causal environmental processes, accounting for genetic contributions. We also provide an overview of recent molecular genetic approaches that utilize genome-wide association study data which are increasingly being applied to questions relevant to psychopathology research. While genetically informative designs typically have been applied to investigate the origins of psychopathology, we highlight how these approaches can also be used to elucidate potential causal environmental processes that contribute to developmental course and outcomes. We highlight the need to use genetically sensitive designs that align with intervention and prevention science efforts, by considering strengths-based environments to investigate how positive environments can mitigate risk and promote children's strengths.

Prenatal programming of developmental trajectories for obesity risk and early pubertal timing

The thrifty phenotype and fetal overnutrition hypotheses are two developmental hypotheses that originated from the developmental origins of health and disease (DOHaD) perspective. The DOHaD posits that exposures experienced prenatally and early in life may influence health outcomes through altering form and function of internal organs related to metabolic processes. Obesity risk and early pubertal timing might be influenced by similar mechanisms. The thrifty phenotype hypothesis is primarily characterized by experiencing a deprivation of nutrients during gestation paired with an energy rich postnatal environment. The fetal overnutrition hypothesis says that obesity experienced prenatally will be associated with increased lifetime risk of obesity in the offspring. Both hypotheses were tested by examining developmental pathways from genetic and prenatal risk through early growth trajectories (birth to 7 years) to pubertal timing at age 11 years. Participants included 361 children adopted at birth (57% male; 57% non-Hispanic White, 11% Black, 9% Hispanic; adoptive family income Mdn = $70,000-$100,000, birth family income Mdn = < $15,000). Associations between boys' childhood body mass index (BMI) and pubertal timing were confounded by genetics, prenatal risk, and early growth. The thrifty phenotype hypothesis was partially supported for boys' childhood BMI (at ages 4 to 7 years). Both hypotheses were partially supported for girls' childhood BMI but not pubertal timing. A novel Gene × Prenatal Risk interaction showed that genetic risk predicted girls' childhood BMI most strongly at adequate compared with at excessive levels of gestational weight gain. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Gene-environment interaction using polygenic scores: Do polygenic scores for psychopathology moderate predictions from environmental risk to behavior problems?

The DNA revolution has energized research on interactions between genes and environments (GxE) by creating indices of G (polygenic scores) that are powerful predictors of behavioral traits. Here, we test the extent to which polygenic scores for attention-deficit/hyperactivity disorder and neuroticism moderate associations between parent reports of their children's environmental risk (E) at ages 3 and 4 and teacher ratings of behavior problems (hyperactivity/inattention, conduct problems, emotional symptoms, and peer relationship problems) at ages 7, 9 and 12. The sampling frame included up to 6687 twins from the Twins Early Development Study. Our analyses focused on relative effect sizes of G, E and GxE in predicting behavior problems. G, E and GxE predicted up to 2%, 2% and 0.4%, respectively, of the variance in externalizing behavior problems (hyperactivity/inattention and conduct problems) across ages 7, 9 and 12, with no clear developmental trends. G and E predictions of emotional symptoms and peer relationship problems were weaker. A quarter (12 of 48) of our tests of GxE were nominally significant (p = .05). Increasing the predictive power of G and E would enhance the search for GxE.

Developmental profiles of child behavior problems from 18 months to 8 years: The protective effects of structured parenting vary by genetic risk

Some children are more affected by specific family environments than others, as a function of differences in their genetic make-up. However, longitudinal studies of genetic moderation of parenting effects during early childhood have not been conducted. We examined developmental profiles of child behavior problems between 18 months and age 8 in a longitudinal parent-offspring sample of 361 adopted children. In toddlerhood (18 months), observed structured parenting indexed parental guidance in service of task goals. Biological parent psychopathology served as an index of genetic influences on children's behavior problems. Four profiles of child behavior problems were identified: low stable (11%), average stable (50%), higher stable (29%), and high increasing (11%). A multinominal logistic regression analysis indicated a genetically moderated effect of structured parenting, such that for children whose biological mother had higher psychopathology, the odds of the child being in the low stable group increased as structured parenting increased. Conversely, for children whose biological mother had lower psychopathology, the odds of being in the low stable group was reduced when structured parenting increased. Results suggest that increasing structured parenting is an effective strategy for children at higher genetic risk for psychopathology, but may be detrimental for those at lower genetic risk.

Impact of hair type, hair sample weight, external hair exposures, and race on cumulative hair cortisol

The biomarker cortisol assesses the impact of biopsychosocial stressors that activate the stress response system. Hair has emerged as a valid and non-invasive means of gauging cumulative cortisol deposited over month-long periods of time. Established protocols for the extraction of hair cortisol are being validated and refined in humans, yet methodological information about hair characteristics on cortisol remains limited. In addition to external hair exposures (e.g. dye, time spent outside), we examined hair categorization or type (e.g. kinky, straight) by extending a hair typing methodology for scientific use that is currently popular among hair care professionals. We then examined the interaction between hair type and race on cortisol levels with a hair questionnaire. Three studies were pooled to investigate how sample weight, hair type, race, heat exposures, and hair treatments impacted cumulative hair cortisol concentrations. Study 1 consisted of Adult Kenyan Medical Workers (N = 44); Study 2 Mexican and Mexican Americans (N = 106); and Study 3 American Youth (N = 107). We found significantly higher cortisol in 5 mg of hair when compared to larger sample weights, and higher cortisol in those who spent more time outdoors. Cortisol concentrations differed between racial groups and varied by hair type; moreover, there were directional differences in cumulative cortisol from straighter to curlier hair types which depended on racial group. In addition to demonstrating the impact of relatively novel control factors like hair sample weight, outdoor exposure, and hair type, the present study illustrates the importance of disentangling hair type and race to understand variability in cumulative hair cortisol. These influences should be included in future studies that measure hair cortisol.

Examining Research Domain Criteria (RDoC) constructs for anger expression and regulation in toddlers

The present study is focused on anger expression and regulation within the National Institute of Mental Health (NIMH) Research Domain Criteria (RDoC) construct of Frustrative Nonreward. Although previous studies have examined associations between child anger regulation and expression, these studies do not directly address the dynamic processes involved in Frustrative Nonreward using microlongitudinal methods. The current study used data from 561 adopted children, their adoptive parents, and birth parents and aimed to address gaps in the literature by examining: (a) temporal associations between anger expression during a frustrating situation, and behaviors thought to regulate emotions (e.g., attempt-to-escape, support-seeking, distraction, and focus-on-restraint) on a microlongitudinal scale during an arm restraint task assessed at 27 months; (b) birth parent externalizing problems and overreactive parenting by adoptive parents as predictors of child anger expression and moderators of the moment-to-moment associations estimated in Step 1; and (c) longitudinal associations (linear vs. quadratic) between anger expressions and externalizing behaviors at 4.5 years. Findings indicated that children's attempt-to-escape and support-seeking predicted an increase in anger expression in the following 3-s interval, whereas distraction and focus-on-restraint were not associated with changes in anger expression. Furthermore, we found that birth parents' externalizing problems were significantly associated with child anger expression, suggesting heritable influences. Anger expression showed a U-shaped longitudinal association with paternal report of externalizing behaviors at 4.5 years. Taken together, the findings emphasize the significance of integrating microlongitudinal analysis approaches into the RDoC framework, helping to advance our understanding of dynamic processes underlying reactions to Frustrative Nonreward. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Illuminating the origins of the intergenerational transmission of psychopathology with a novel genetically informed design

Although it is well known that parental depression is transmitted within families across generations, the etiology of this transmission remains unclear. Our goal was to develop a novel study design capable of explicitly examining the etiologic sources of intergenerational transmission. We specifically leveraged naturally-occurring variations in genetic relatedness between parents and their adolescent children in the 720 families participating in the Nonshared Environment in Adolescent Development (NEAD) study, 58.5% of which included a rearing stepparent (nearly always a stepfather). Results pointed squarely to the environmental transmission of psychopathology between fathers and children. Paternal depression was associated with adolescent depression and adolescent behavior problems (i.e., antisocial behavior, headstrong behavior, and attention problems) regardless of whether or not fathers and their children were genetically related. Moreover, these associations persisted to a subset of "blended" families in which the father was biologically related to one participating child but not to the other, and appeared to be mediated via father-child conflict. Such findings are not only fully consistent with the environmental transmission of psychopathology across generations, but also add to extant evidence that parent-child conflict is a robust and at least partially environmental predictor of adolescent psychopathology.

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.

Early manifestations of intellectual performance: Evidence that genetic effects on later academic test performance are mediated through verbal performance in early childhood

Intellectual performance is highly heritable and robustly predicts lifelong health and success but the earliest manifestations of genetic effects on this asset are not well understood. This study examined whether early executive function (EF) or verbal performance mediate genetic influences on subsequent intellectual performance, in 561 U.S.-based adoptees (57% male) and their birth and adoptive parents (70% and 92% White, 13% and 4% African American, 7% and 2% Latinx, respectively), administered measures in 2003-2017. Genetic influences on children's academic performance at 7 years were mediated by verbal performance at 4.5 years (β = .22, 95% CI [0.08, 0.35], p = .002) and not via EF, indicating that verbal performance is an early manifestation of genetic propensity for intellectual performance.

Reexamining the association between the interparental relationship and parent-child interactions: Incorporating heritable influences

Family systems research has identified two key processes (spillover and compensatory), linking interparental relationship quality to the parent-child relationship. However, previous research has focused on the parent as the sole initiator and had not often considered the role of the child in these processes. The present study adds to the literature by leveraging a genetically informed design to examine possible child evocative effects on spillover and compensatory processes. Participants were from a longitudinal parent-offspring adoption sample of 361 linked sets of adoptive parents of an adopted child (57% male), and the child's birth parents. Adoptive parents reported on child pleasure and anger at 18 months and the interparental relationship at 27 months. Parent-child interactions were observed at child age 6 years, and heritable influences were assessed via birth mother self-report at 5 months. Our results indicated a dampening effect where higher interparental warmth at child age 27 months was associated with less adoptive mother-child coercion at child age 6 years, and a compensatory effect where higher interparental conflict was associated with more adoptive father-child positive engagement. Moreover, our results indicated child-driven effects via both genetic and environmental pathways. Specifically, higher levels of birth mother negative affect (heritable characteristic) were associated with lower levels of adoptive father-child coercion. Also, child anger was positively associated with interparental conflict, and child pleasure was positively associated with interparental warmth. These findings support findings from the family literature with evidence of compensatory mechanisms, while also highlighting the active role children play in shaping family interactions. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The role of child negative emotionality in parenting and child adjustment: Gene-environment interplay

BACKGROUND

Evocative gene-environment correlation (rGE) describes a process through which children's heritable characteristics influence their rearing environments. The current study examined whether heritable influences on parenting and children's behavioural outcomes operate through child negative emotionality.

METHOD

Using data from the Early Growth and Development Study, we examined associations among adoptive parent reports of child anger and sadness at 4.5 years, adoptive parents' hostile and warm parenting at 6 years and child behavioural problems and social competence at age 7. Birth parent temperament was included to test whether child effects on parents reflect evocative gene-environment correlation (rGE).

RESULTS

Child anger at 4.5 years evoked hostile parenting from adoptive parents at 6 years, which was subsequently related to child problem behaviours at 7 years. Evocative rGE effects were identified for adoptive parents' hostile parenting.

CONCLUSIONS

By employing a genetically informed design, we found that birth parent temperament was related to child negative emotionality. Adoptive parents were sensitive to child negative emotionality, and this sensitivity was linked to the child's later adjustment.

Nine Levels of Explanation : A Proposed Expansion of Tinbergen's Four-Level Framework for Understanding the Causes of Behavior

Tinbergen's classic "On Aims and Methods of Ethology" (Zeitschrift für Tierpsychologie, 20, 1963) proposed four levels of explanation of behavior, which he thought would soon apply to humans. This paper discusses the need for multilevel explanation; Huxley and Mayr's prior models, and others that followed; Tinbergen's differences with Lorenz on "the innate"; and Mayr's ultimate/proximate distinction. It synthesizes these approaches with nine levels of explanation in three categories: phylogeny, natural selection, and genomics (ultimate causes); maturation, sensitive period effects, and routine environmental effects (intermediate causes); and hormonal/metabolic processes, neural circuitry, and eliciting stimuli (proximate causes), as a respectful extension of Tinbergen's levels. The proposed classification supports and builds on Tinbergen's multilevel model and Mayr's ultimate/proximate continuum, adding intermediate causes in accord with Tinbergen's emphasis on ontogeny. It requires no modification of Standard Evolutionary Theory or The Modern Synthesis, but shows that much that critics claim was missing was in fact part of Neo-Darwinian theory (so named by J. Mark Baldwin in The American Naturalist in 1896) all along, notably reciprocal causation in ontogeny, niche construction, cultural evolution, and multilevel selection. Updates of classical examples in ethology are offered at each of the nine levels, including the neuroethological and genomic findings Tinbergen foresaw. Finally, human examples are supplied at each level, fulfilling his hope of human applications as part of the biology of behavior. This broad ethological framework empowers us to explain human behavior-eventually completely-and vindicates the idea of human nature, and of humans as a part of nature.

Impact of prenatal exposure characterization on early risk detection: Methodologic insights for the HEALthy Brain and Child Development (HBCD) study

BACKGROUND

A major challenge in prenatal drug exposure research concerns the balance of measurement quality with sample sizes necessary to address confounders. To inform the selection of optimal exposure measures for the HEALthy Brain and Child Development (HBCD) Study, we employed integrated analysis to determine how different methods used to characterize prenatal tobacco exposure influence the detection of exposure-related risk, as reflected in normal variations in birth weight.

METHODS

Participants were N = 2323 mother-infant dyads derived from 7 independent developmental cohorts harmonized on measures of exposure, outcome (birthweight), and covariates. We compared estimates of PTE-related effects on birthweight derived from linear regression models when PTE was categorized dichotomously based on any fetal exposure (30% exposed; 69% not exposed); versus categorically, based on common patterns of maternal smoking during pregnancy (never smoked 69%; quit smoking 16%; smoked intermittently 2%; smoked persistently 13%). We secondarily explored sex differences in PTE-birthweight associations across these categorization methods.

RESULTS

When PTE was categorized dichotomously, exposure was associated with a - 125-g difference in birthweight (95% C.I. -173.7 - -76.6, p < .0001). When PTE was characterized categorically based on maternal smoking patterns, however, exposure was associated with either no difference in birthweight if mothers quit smoking by the end of the first trimester (B = -30.6, 95% C.I. -88.7-27.4, p = .30); or a - 221.8 g difference in birthweight if mothers did not [95% C.I. (-161.7 to -282.0); p < .001]. Qualitative sex differences were also detected though PTE x sex interactions did not reach statistical significance. Maternal smoking cessation during pregnancy was associated with a 239.3 g increase in birthweight for male infants, and a 114.0 g increase in birthweight for females infants (p = .07).

CONCLUSIONS

Categorization of PTE based on patterns of maternal smoking rather than the presence or absence of exposure alone revealed striking nuances in estimates of exposure-related risk. The described method that captures both between-individual and within-individual variability in prenatal drug exposure is optimal and recommended for future developmental investigations such as the HBCD Study.

Do I Look Gawky? The Association between Pubertal Asynchrony and Peer Victimization

Pubertal synchrony is defined as the degree of coherence to which puberty-related body changes (e.g., breast development, growth spurt, voice change, underarm hair growth) are coordinated. During the pubertal transition, youth’s body parts grow asynchronously, making each youth’s physical appearance unique. Physical appearance is a known correlate of youth’s psychosocial functioning during adolescence, but we know little about how pubertal asynchrony plays a role in their peer relationships. Using data from an adoption study (the Early Growth and Development Study; n = 413; 237 boys, 176 girls), this study examined the effect of pubertal asynchrony on peer victimization. Results revealed sex-specific effects of pubertal asynchrony; pubertal asynchrony was associated with a higher risk of peer victimization for girls but a lower risk for boys. Findings highlight the intersection of physical development and social context in understanding youth’s experiences of puberty.

Gene × Environment Interactions in the Development of Preschool Effortful Control, and Its Implications for Childhood Externalizing Behavior

This study examined the role of gene × environment interaction (G × E) in the development of effortful control (EC) and externalizing symptoms (EXT). Participants included 361 adopted children, and their Adoptive Parents (APs) and Birth Mothers (BMs), drawn from the Early Growth and Development Study. The primary adoptive caregivers' (AP1) laxness and overreactivity were assessed when children were 27-months-old, and used as indices of environmental influences on EC. Heritable influences on child EC were assessed by the BMs' personality characteristics (emotion dysregulation, agreeableness). Secondary adoptive caregivers (AP2) reported on children's EC at 54 months, and EXT at 7 years. Interactions between BM characteristics and AP1 laxness were related to EC and indirectly predicted EXT via EC. Parental laxness and EC were positively associated if children had high heritable risk for poor EC (BM high emotion dysregulation or low agreeableness), but negatively associated if children had low heritable risk for poor EC (BM low emotion dysregulation or high agreeableness). BM agreeableness also moderated associations between AP1 overreactivity and effortful control, and yielded a similar pattern of results. Our findings suggest that G × E is an important first step in the development of EXT via its effect on EC. Consistent with "goodness of fit" models, heritable tendencies can affect which parenting practices best support EC development.

Systematic Review and Meta-analysis of Genetically Informed Research: Associations Between Parent Anxiety and Offspring Internalizing Problems

OBJECTIVE

Parent anxiety is associated with offspring internalizing problems (emotional problems related to anxiety and depression). This may reflect causal processes, whereby exposure to parent anxiety directly influences offspring internalizing (and/or vice versa). However, parent-offspring associations could also be attributable to their genetic relatedness. A systematic review and meta-analysis were conducted to investigate whether exposure to parent anxiety is associated with offspring internalizing after controlling for genetic relatedness.

METHOD

A literature search across 5 databases identified 429 unique records. Publications were retained if they used a quasi-experimental design in a general population sample to control for participant relatedness in associations between parent anxiety and offspring internalizing outcomes. Publications were excluded if they involved an experimental exposure or intervention. Studies of prenatal and postnatal anxiety exposure were meta-analyzed separately. Pearson's correlation coefficient estimates (r) were pooled using multilevel random-effects models.

RESULTS

Eight publications were retained. Data were drawn from 4 population cohorts, each unique to a quasi-experimental design: adoption, sibling-comparison, children-of-twins or in vitro fertilization. Cohorts were located in northern Europe or America. Families were predominantly of European ancestry. Three publications (Nfamilies >11,700; offspring age range, 0.5-10 years) showed no association between prenatal anxiety exposure and offspring internalizing outcomes after accounting for participant relatedness (r = .04; 95% CI: -.07, .14). Six publications (Nfamilies >12,700; offspring age range, 0.75-22 years) showed a small but significant association between concurrent symptoms in parents and offspring after accounting for participant relatedness (r = .13; 95% CI: .04, .21).

CONCLUSION

Initial literature, derived from homogeneous populations, suggests that prenatal anxiety exposure does not cause offspring internalizing outcomes. However, postnatal anxiety exposure may be causally associated with concurrent offspring internalizing via nongenetic pathways. Longitudinal stability, child-to-parent effects, and the role of moderators and methodological biases require attention.

Shared Environment and Genetics Shape the Gut Microbiome after Infant Adoption

The composition of the human gut microbiome is highly variable, and this variation has been repeatedly tied to variation in human health. However, the sources of microbial variation remain unclear, especially early in life. It is particularly important to understand sources of early life variation in the microbiome because the state of the microbiome in childhood can influence lifelong health. Here, we compared the gut microbiomes of children adopted in infancy to those of genetically unrelated children in the same household and genetically related children raised in other households. We observed that a shared home environment was the strongest predictor of overall microbiome similarity. Among those microbial taxa whose variation was significantly explained by our models, the abundance of a given taxon was more frequently explained by host genetic similarity (relatedness), while the presence of a given taxon was more dependent upon a shared home environment. This suggests that although the home environment may act as a species source pool for the gut microbiome in childhood, host genetic factors likely drive variation in microbial abundance once a species colonizes the gut.IMPORTANCE Our results demonstrate that the early life home environment can significantly alter the gut microbiome in childhood, potentially altering health outcomes or risk for adverse health outcomes. A better understanding of the drivers of gut microbiome variation during childhood could lead to more effective intervention strategies for overall health starting in early life.

The role of negative emotionality in the development of child executive function and language abilities from toddlerhood to first grade: An adoption study

Understanding the role of negative emotionality in the development of executive functioning (EF) and language skills can help identify developmental windows that may provide promising opportunities for intervention. In addition, because EF and language skills are, in part, genetically influenced, intergenerational transmission patterns are important to consider. The prospective parent-offspring adoption design used in this study provides a unique opportunity to examine the intergenerational transmission of EF and language skills. Participants were 561 children adopted around the time of birth. Accounting for birth mother EF and language contributions, we examined the role of child negative emotionality in toddlerhood (age 9 to 27 months) and childhood (age 4.5 to 7 years) on child EF and language skills in first grade (age 7 years). There was continuity in EF from age 27 months to 7 years, and in language ability from age 27 months to 7 years, with no cross-lagged effects between child EF and language ability. Negative emotionality at age 9 months predicted lower EF and lower language abilities at age 7 years, and growth in negative emotionality from age 4.5 to 7 years predicted lower child EF at age 7 years. Overall, findings suggested that lower negative emotionality at age 9 months was associated with higher toddler and child EF and language skills and that preventing growth in negative emotionality from age 4.5 to 7 years may lead to improvements in child EF. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Disentangling nature from nurture in examining the interplay between parent-child relationships, ADHD, and early academic attainment

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is highly heritable and is associated with lower educational attainment. ADHD is linked to family adversity, including hostile parenting. Questions remain regarding the role of genetic and environmental factors underlying processes through which ADHD symptoms develop and influence academic attainment.

METHOD

This study employed a parent-offspring adoption design (N = 345) to examine the interplay between genetic susceptibility to child attention problems (birth mother ADHD symptoms) and adoptive parent (mother and father) hostility on child lower academic outcomes, via child ADHD symptoms. Questionnaires assessed birth mother ADHD symptoms, adoptive parent (mother and father) hostility to child, early child impulsivity/activation, and child ADHD symptoms. The Woodcock-Johnson test was used to examine child reading and math aptitude.

RESULTS

Building on a previous study (Harold et al., 2013, Journal of Child Psychology and Psychiatry, 54(10), 1038-1046), heritable influences were found: birth mother ADHD symptoms predicted child impulsivity/activation. In turn, child impulsivity/activation (4.5 years) evoked maternal and paternal hostility, which was associated with children's ADHD continuity (6 years). Both maternal and paternal hostility (4.5 years) contributed to impairments in math but not reading (7 years), via impacts on ADHD symptoms (6 years).

CONCLUSION

Findings highlight the importance of early child behavior dysregulation evoking parent hostility in both mothers and fathers, with maternal and paternal hostility contributing to the continuation of ADHD symptoms and lower levels of later math ability. Early interventions may be important for the promotion of child math skills in those with ADHD symptoms, especially where children have high levels of early behavior dysregulation.

Psychopathology Symptoms are Associated with Prenatal Health Practices in Pregnant Women with Heavy Smoking Levels

PURPOSE

Smoking during pregnancy may be linked to other problematic prenatal health behaviors in women. We examined interrelationships among prenatal smoking, prenatal health behaviors and mental health. The objective of this study was to examine factors that may contribute to variations in prenatal health practices among women who smoke during pregnancy.

METHODS

Birth mothers from an adoption study (N = 912) were interviewed about prenatal smoking, health behaviors, and mental health symptoms at 5 months postpartum.

RESULTS

One-quarter of participants (N = 222) reported smoking 6 or more cigarettes daily for at least 1 trimester. For mothers who smoked more than 6 cigarettes daily, higher levels of antisocial behaviors (β =  - .14, p = .03) and depressive symptoms (β =  - .17, p = .03) were associated with less frequent prenatal folate use; antisocial behaviors and depressive symptoms were not associated for prenatal folate use among women who did not smoke more than 6 cigarettes daily. For mothers who did not smoke more than 6 cigarettes daily, more depressive symptoms were associated with fewer prenatal care visits (β = .12, p = .01). Antisocial behaviors and anxiety symptoms were not associated with prenatal care visits in either group of mothers. CONCLUSIONS FOR PRACTICE: Maternal antisocial behaviors and depressive symptoms during pregnancy may be markers for poorer adherence to recommendations for folate supplementation among women who smoke 6 or more cigarettes daily during pregnancy, independent of adequacy of prenatal care.

Fertility Problems and Parenting Daily Hassles in Childhood: A 7-year Longitudinal Study of Adoptive Parents

Fertility problems are known to exert a negative impact on psychological health. Meanwhile, individuals with fertility challenges often view adoption as a positive healing experience. Yet, a dearth of work has examined the long-term impact that fertility problems have on adoptive parents and their childrearing stress. Here, we investigated how fertility problems related to parenting daily hassle (PDH) trajectories among adoptive mothers and fathers in the Early Growth and Development Study (N = 333). When adopted children were 9 months old, adoptive parents reported whether they had fertility problems prior to their decision to adopt and rated their PDH frequency and intensity on six occasions over the next 7 years. Multilevel models revealed inverse U-shaped curves for PDH among both fertile and infertile parents, such that PDH increased from child age 9 months until about 5 to 6 years and decreased thereafter. Mothers with fertility problems exhibited a steeper PDH incline from 9 months to the peak at child age 5 to 6, but also incurred a swifter subsequent decline. There were no significant differences in fathers' PDH trajectories based on fertility problems. We discuss why fertility problems appear to impact PDH trajectories for mothers rather than fathers.

Maternal Consistency in Recalling Prenatal Experiences at 6 Months and 8 Years Postnatal

OBJECTIVE

Mothers are known to be reliable reporters of smoking during pregnancy, type of delivery, and birth weight when compared with medical records. Few studies have considered whether the timing of retrospective collection affects the mother's retrospective self-report. We examined the consistency of maternal retrospective recall of prenatal experiences, behaviors, and basic birth outcomes between 6 months and 8 years postpartum.

METHOD

We examined 117 mothers (62% White, 44% living in a committed relationship, median high school education) from the Early Growth and Development Study (EGDS). EGDS is a longitudinal adoption study that includes birth mothers of children born between 2003 and 2009 who were involved in a domestic adoption. Using the modified life history calendar and a pregnancy screener, mothers reported on their prenatal health behaviors, prenatal substance use, and labor and delivery at 6 months and 8 years postpartum. Cohen κ was calculated to examine consistency, and χ tests were used to test differences by parity and maternal education.

RESULTS

Mothers' recall was very good for recall of the type of delivery and good for smoking during pregnancy, medicine used for labor induction, and specific medical problems (i.e., pre-eclampsia, sexually transmitted infections, and kidney infections). Recall consistency was poor for illicit drug use, specific prenatal tests performed (i.e., amniocentesis and emergency room visits), and using drugs other than an epidural during delivery.

CONCLUSION

This study provides support for using retrospective collection of maternal self-report on some prenatal experiences up to 8 years postpartum and offers a potential way to more accurately collect self-reported prenatal experiences.

The intergenerational transmission of mathematics achievement in middle childhood: A prospective adoption design

The present study uses a parent-offspring adoption design to examine the dual roles of heritable and environmental influences on children's mathematics achievement. Linked sets (N = 195) of adopted children, adoptive parents, and birth parents each completed a measure of mathematics fluency (i.e., simple computational operations). Birth parent mathematics achievement and adoptive father mathematics achievement positively correlated with child achievement scores at age 7, whereas adoptive mother and adopted child mathematics achievement scores were not significantly associated with one another. Additionally, findings demonstrated no significant effects of gene-environment interactions on child mathematics achievement at age 7. These results indicate that both heritable and rearing environmental factors contribute to children's mathematics achievement and identify unique influences of the paternal rearing environment on mathematics achievement in middle childhood.

Inherited and Environmental Moderators of Mother-Child Behavioral Contingency and Contingent Negativity at 27 Months

Previous research has shown that as depressive symptomology increases, mothers tend to show withdrawn or harsh interaction patterns with their children, and the quality of these interaction patterns have subsequently been linked to child behavior problems. However, little research has examined bidirectional influences between mothers and their children, and how these moment-to-moment contingencies differ based on heritable and environmental characteristics. We used data from the Early Growth and Development Study a prospective adoption study to examine how adoptive mothers' depressive symptoms and children's heritable tendencies for negative affectivity interact to predict the quality of mother-child interactions at child age 27-months. Results detected two distinct dyadic interaction patterns. The first was a withdrawn interaction style and was observed in children with a high heritable tendency for negative affect. In that style, mother and child interactions were not contingent upon each other, suggesting a lack of joint engagement. The second was a volatile interaction style, observed in children with a low heritable tendency for negative affect. In these cases, mother and child interactions were highly contingent but negative. Our findings demonstrate essential differences in how dyadic interaction patterns vary according to level of depressive symptomology and heritable tendency for negative affect.

Child Effects on Parental Negativity: The Role of Heritable and Prenatal Factors

This study examined two possible mechanisms, evocative gene-environment correlation and prenatal factors, in accounting for child effects on parental negativity. Participants included 561 children adopted at birth, and their adoptive parents and birth parents within a prospective longitudinal adoption study. Findings indicated child effects on parental negativity, such that toddlers' negative reactivity at 18 months was positively associated with adoptive parents' over-reactive and hostile parenting at 27 months. Furthermore, we found that child effects on parental negativity were partially due to heritable (e.g., birth mother [BM] internalizing problems and substance use) and prenatal factors (e.g., BM illicit drug use during pregnancy) that influence children's negative reactivity at 18 months. This study provides critical evidence for "child on parent" effects.

Using a sibling-adoption design to parse genetic and environmental influences on children's body mass index (BMI)

Dietary and physical activity behaviors formed early in life can increase risk for childhood obesity and have continued negative consequences for lifelong health. Previous research has highlighted the importance of both genetic and environmental (e.g., cultural environment or parental lifestyle) contributions to obesity risk, although these studies typically involve genetically-related individuals residing in the same household, where genetic similarity and rearing environment are inextricably linked. Here we utilize a sibling-adoption design to independently estimate genetic and environmental contributions to obesity risk in childhood and describe how these influences might vary as children age. As part of a prospective adoption study, the current investigation used data from biological siblings reared either apart or together, and nonbiological siblings reared together to estimate the contributions of genetics and environment to body mass indices (BMI) in a large cohort of children (N = 711). We used a variance partitioning model to allocate variation in BMI to that which is due to shared genetics, common environment, or unique environment in this cohort during middle childhood and adolescence. We found 63% of the total variance in BMI could be attributed to heritable factors in middle childhood sibling pairs (age 5-11.99; 95% CI [0.41,0.85]). Additionally, we observed that common environment explained 31% of variation in BMI in this group (95% CI [0.11,0.5]), with unique environment and error explaining the remaining variance. We failed to detect an influence of genetics or common environment in older sibling pairs (12-18) or pairs spanning childhood and adolescence (large sibling age difference), but home type (adoptive versus birth) was an important predictor of BMI in adolescence. The presence of strong common environment effects during childhood suggests that early interventions at the family level in middle childhood could be effective in mitigating obesity risk in later childhood and adolescence.

Using an adoption design to test genetically based differences in risk for child behavior problems in response to home environmental influences

Differential susceptibility theory (DST) posits that individuals differ in their developmental plasticity: some children are highly responsive to both environmental adversity and support, while others are less affected. According to this theory, "plasticity" genes that confer risk for psychopathology in adverse environments may promote superior functioning in supportive environments. We tested DST using a broad measure of child genetic liability (based on birth parent psychopathology), adoptive home environmental variables (e.g., marital warmth, parenting stress, and internalizing symptoms), and measures of child externalizing problems (n = 337) and social competence (n = 330) in 54-month-old adopted children from the Early Growth and Development Study. This adoption design is useful for examining DST because children are placed at birth or shortly thereafter with nongenetically related adoptive parents, naturally disentangling heritable and postnatal environmental effects. We conducted a series of multivariable regression analyses that included Gene × Environment interaction terms and found little evidence of DST; rather, interactions varied depending on the environmental factor of interest, in both significance and shape. Our mixed findings suggest further investigation of DST is warranted before tailoring screening and intervention recommendations to children based on their genetic liability or "sensitivity."

History of breastfeeding but not mode of delivery shapes the gut microbiome in childhood

BACKGROUND

The naïve neonatal gut is sensitive to early life experiences. Events during this critical developmental window may have life-long impacts on the gut microbiota. Two experiences that have been associated with variation in the gut microbiome in infancy are mode of delivery and feeding practices (eg, breastfeeding). It remains unclear whether these early experiences are responsible for microbial differences beyond toddlerhood.

AIMS

Our study examined whether mode of delivery and infant feeding practices are associated with differences in the child and adolescent microbiome.

DESIGN, SUBJECTS, MEASURES

We used an adoption-sibling design to compare genetically related siblings who were reared together or apart. Gut microbiome samples were collected from 73 children (M = 11 years, SD = 3 years, range = 3-18 years). Parents reported on child breastfeeding history, age, sex, height, and weight. Mode of delivery was collected through medical records and phone interviews.

RESULTS

Negative binomial mixed effects models were used to identify whether mode of delivery and feeding practices were related to differences in phylum and genus-level abundance of bacteria found in the gut of child participants. Covariates included age, sex, and body mass index. Genetic relatedness and rearing environment were accounted for as random effects. We observed a significant association between lack of breastfeeding during infancy and a greater number of the genus Bacteroides in stool in childhood and adolescence.

CONCLUSION

The absence of breastfeeding may impart lasting effects on the gut microbiome well into childhood.

The Intergenerational Transmission of Early Educational Advantages: New Results Based on an Adoption Design

Sociological research has traditionally emphasized the importance of post-birth factors (i.e., social, economic, and cultural capital) in the intergenerational transmission of educational advantages, to the neglect of potentially consequential pre-birth endowments (e.g., heritable traits) that are passed from parent to child. In this study, we leverage an experiment of nurture-children who were adopted at birth into nonrelative families-in an effort to simultaneously model the effects associated with both pathways. To do so, we fit a series of simple linear regression models that relate the academic achievement of adopted children to the educational attainments of their adoptive and biological parents, using U.S. data from a recent nationwide sample of birth and adoptive families (the Early Growth and Development Study). Because our dataset includes both "genetic" and "environmental" relatives, but not "genetic-and-environmental" relatives, the separate contributions of each pathway can be identified, as well as possible interactions between the two. Our results show that children's early achievements are influenced not only by the attainments of their adoptive parents, but also the attainments of their birth parents-suggesting the presence of environmental and genetically mediated effects. Supplementary analyses provide little evidence of effect moderation, using both distal and proximate measures of the childhood environment to model gene-by-environment interactions. These findings are robust to a variety of parameterizations, withstand a series of auxiliary checks, and remain intact even after controlling for intrauterine exposures and other measurable variables that could compromise our design. The implications of our results for theory and research in the stratification literature, and for those interested in educational mobility, are discussed.