Naturalistic experimental designs as tools for understanding the role of genes and the environment in prevention research

Before genetic approaches were applied in experimental studies with human populations, they were used by animal and plant breeders to observe, and experimentally manipulate, the role of genes and environment on specific phenotypic or behavioral outcomes. For obvious ethical reasons, the same level of experimental control is not possible in human populations. Nonetheless, there are natural experimental designs in human populations that can serve as logical extensions of the rigorous quantitative genetic experimental designs used by animal and plant researchers. Applying concepts such as cross-fostering and common garden rearing approaches from the life science discipline, we describe human designs that can serve as naturalistic proxies for the controlled quantitative genetic experiments facilitated in life sciences research. We present the prevention relevance of three such human designs: (1) children adopted at birth by parents to whom they are not genetically related (common garden approach); (2) sibling designs where one sibling is reared from birth with unrelated adoptive parents and the other sibling is reared from birth by the biological mother of the sibling pair (cross-fostering approach); and (3) in vitro fertilization designs, including egg donation, sperm donation, embryo donation, and surrogacy (prenatal cross-fostering approach). Each of these designs allows for differentiation of the effects of the prenatal and/or postnatal rearing environment from effects of genes shared between parent and child in naturalistic ways that can inform prevention efforts. Example findings from each design type are provided and conclusions drawn about the relevance of naturalistic genetic designs to prevention science

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

A plethora of studies with parents and children who are biologically related has shown that the family environment plays an important role in child development. However, scientists have long known that a rigorous examination of environmental effects requires research designs that go beyond studies of genetically-linked family members. Harnessing the principles of sibling comparison and animal cross-fostering designs, we introduce a novel approach: the siblings-reared-apart design. Supplementing the traditional adoption design of adopted child and adoptive parents with a sample of the adopted children’s birth parents who raised their biological child(ren) at home (i.e., biological siblings of adoptees), this design provides opportunities to evaluate the role of specific rearing environments. In this proof of concept approach, we tested whether rearing environments differed between adoptive and birth families. Using data from 118 sets of adoption-linked families, each consisting of an adoptive family and the adoptee’s birth family, both of whom are raising at least a child in each home, we found that compared with families in the birth homes, (a) adoptive families had higher household incomes and maternal educational attainment; (b) adoptive mothers displayed more guiding parenting, less harsh parenting, and less maternal depression; and (c) socioeconomic differences between the two homes did not account for the behavioral differences in mothers. We discuss the potential of the sibling-reared-apart design to advance developmental science

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 173 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 = 326 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 their inhibitory control and peer behavior. Implications for the development of evidence-based interventions are discussed

Toward an Understanding of the Role of the Environment in the Development of Early Callous Behavior

Key to understanding the long‐term impact of social inequalities is identifying early behaviors that may signal higher risk for later poor psychosocial outcomes, such as psychopathology. A set of early‐emerging characteristics that may signal risk for later externalizing psychopathology is callous‐unemotional (CU) behavior. CU behavior predicts severe and chronic trajectories of externalizing behaviors in youth. However, much research on CU behavior has focused on late childhood and adolescence, with little attention paid to early childhood when preventative interventions may be most effective. In this article, we summarize our recent work showing that (a) CU behavior can be identified in early childhood using items from common behavior checklists, (b) CU behavior predicts worse outcomes across early childhood, (c) CU behavior exhibits a nomological network distinct from other early externalizing behaviors, and (d) malleable environmental factors, particularly parenting, may play a role in the development of early CU behaviors. We discuss the challenges of studying contextual contributors to the development of CU behavior in terms of gene–environment correlations and present initial results from work examining CU behavior in an adoption study in which gene–environment correlations are examined in early childhood. We find that parenting is a predictor of early CU behavior even in a sample in which parents are not genetically related to the children.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/136006/1/jopy12221_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/136006/2/jopy12221.pd

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

Using an adoption–biological family design to examine associations between maternal trauma, maternal depressive symptoms, and child internalizing and externalizing behaviors

Maternal trauma is a complex risk factor that has been linked to adverse child outcomes, yet the mechanisms underlying this association are not well understood. This study, which included adoptive and biological families, examined the heritable and environmental mechanisms by which maternal trauma and associated depressive symptoms are linked to child internalizing and externalizing behaviors. Path analyses were used to analyze data from 541 adoptive mother–adopted child (AM–AC) dyads and 126 biological mother–biological child (BM–BC) dyads; the two family types were linked through the same biological mother. Rearing mother’s trauma was associated with child internalizing and externalizing behaviors in AM–AC and BM–BC dyads, and this association was mediated by rearing mothers’ depressive symptoms, with the exception of biological child externalizing behavior, for which biological mother trauma had a direct influence only. Significant associations between maternal trauma and child behavior in dyads that share only environment (i.e., AM–AC dyads) suggest an environmental mechanism of influence for maternal trauma. Significant associations were also observed between maternal depressive symptoms and child internalizing and externalizing behavior in dyads that were only genetically related, with no shared environment (i.e., BM–AC dyads), suggesting a heritable pathway of influence via maternal depressive symptoms

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

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), 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