Siblings reared apart: A sibling comparison study on rearing environment differences

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.

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.

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.

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.

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.

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.

Comparison of Adopted and Nonadopted Individuals Reveals Gene-Environment Interplay for Education in the UK Biobank

Polygenic scores now explain approximately 10% of the variation in educational attainment. However, they capture not only genetic propensity but also information about the family environment. This is because of passive gene-environment correlation, whereby the correlation between offspring and parent genotypes results in an association between offspring genotypes and the rearing environment. We measured passive gene-environment correlation using information on 6,311 adoptees in the UK Biobank. Adoptees' genotypes were less correlated with their rearing environments because they did not share genes with their adoptive parents. We found that polygenic scores were twice as predictive of years of education in nonadopted individuals compared with adoptees (R²s = .074 vs. .037, p = 8.23 × 10^-24). Individuals in the lowest decile of polygenic scores for education attained significantly more education if they were adopted, possibly because of educationally supportive adoptive environments. Overall, these results suggest that genetic influences on education are mediated via the home environment.

Comparison of Adopted and Nonadopted Individuals Reveals Gene-Environment Interplay for Education in the UK Biobank

Polygenic scores now explain approximately 10% of the variation in educational attainment. However, they capture not only genetic propensity but also information about the family environment. This is because of passive gene–environment correlation, whereby the correlation between offspring and parent genotypes results in an association between offspring genotypes and the rearing environment. We measured passive gene–environment correlation using information on 6,311 adoptees in the UK Biobank. Adoptees’ genotypes were less correlated with their rearing environments because they did not share genes with their adoptive parents. We found that polygenic scores were twice as predictive of years of education in nonadopted individuals compared with adoptees (R²s = .074 vs. .037, p = 8.23 × 10⁻²⁴). Individuals in the lowest decile of polygenic scores for education attained significantly more education if they were adopted, possibly because of educationally supportive adoptive environments. Overall, these results suggest that genetic influences on education are mediated via the home environment.

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.

Longitudinal examination of pathways to peer problems in middle childhood: A siblings-reared-apart design

To advance research from Dishion and others on associations between parenting and peer problems across childhood, we used a sample of 177 sibling pairs reared apart since birth (because of adoption of one of the siblings) to examine associations between parental hostility and children's peer problems when children were ages 7 and 9.5 years (n = 329 children). We extended conventional cross-lagged parent-peer models by incorporating child inhibitory control as an additional predictor and examining genetic contributions via birth mother psychopathology. Path models indicated a cross-lagged association from parental hostility to later peer problems. When child inhibitory control was included, birth mother internalizing symptoms were associated with poorer child inhibitory control, which was associated with more parental hostility and peer problems. The cross-lagged paths from parental hostility to peer problems were no longer significant in the full model. Multigroup analyses revealed that the path from birth mother internalizing symptoms to child inhibitory control was significantly higher for birth parent-reared children, indicating the possible contribution of passive gene-environment correlation to this association. Exploratory analyses suggested that each child's unique rearing context contributed to his or her inhibitory control and peer behavior. Implications for the development of evidence-based interventions are discussed.