Using a Siblings Reared Apart and Together Design to Study Associations Between Parenting and Child Behavior Problems

There is a large body of research documenting the association between parenting practices and child behavior problems. A range of mechanisms have been posited for this association, including shared genetic factors (passive... [ view full abstract ]

There is a large body of research documenting the association between parenting practices and child behavior problems. A range of mechanisms have been posited for this association, including shared genetic factors (passive gene-environment correlation), child evocative effects on parenting, and child modeling of parental behavior. Genetically-sensitive studies are uniquely suited to separate genetic and environmental factors that underlie associations between parenting practices and child problems, and intervention studies are uniquely suited to isolate malleable environmental influences on child problems. However, the principles underlying these two paradigms are seldom used in concert with one another, hampering the identification of malleable mechanisms for intervention research. The purpose of this study was to address this gap through the use of a natural experimental design facilitated by an adoption-sibling study. We expected to replicate the well-known association between parenting practices and child behavior problems, to demonstrate that this correlation remains significant in unrelated adoptive parent-child dyads (e.g., passive gene-environment correlation alone cannot explain the association), and to replicate prior studies indicating that child behavior problems are partially heritable using a sibling analysis. 

Participants were drawn from the Early Growth and Development Study, a prospective adoption-sibling study that includes over 500 adoptees who were placed with genetically unrelated adoptive families at birth, and their siblings who either resided in the same home as the adoptee or who had been reared apart since birth. In addition, in some families, there were additional children in the birth parent home who were not genetically related to the adoptee. Thus, the design includes siblings living in the same or different homes since birth who are either genetically-related or genetically unrelated (n = 1285 children, M age = 11.35 yrs, SD = 4.3 years). Mothers completed the Strengths and Difficulties Questionnaire (total behavior problem scale) individually about each of her children and also reported her warm and harsh parenting to each child using the Iowa Family Interaction Rating Scales. Cross-sectional analyses indicated a positive association between child behavior problems and harsh parenting (r = .47) and a negative association between child behavior problems and warm parenting (r = -.19) that was similar when the parent was genetically-related (r = .41 for hostility and r = -.17 for warmth) or unrelated to the child (r = .51 for hostility and r = -.19 for warmth; all p’s < .01 after correcting for multiple testing), suggesting negligible effects of passive gene-environment correlation. Sibling models controlling for age and sex indicated significant heritable (.34) and nonshared environmental variance components (.60) of child behavior problems. Regression analyses predicting parental hostility indicated a significant effect of genetic relatedness of child to parent in the adoptive home, where mothers reported less hostility to children who were genetically related to them, and more hostility toward their adoptee. Results were discussed in terms of the ability of natural experimental designs to provide insights into environmental mechanisms and intervention targets.