Passive rGE is a second way in which children’s inherited qualities can be correlated with their environment. Passive rGE occurs when genes are shared between a rearing parent and a child. Quantitative genetic studies have identified passive rGE influences during middle childhood (e.g., Lemery-Chalfant, et al., 2013) and adolescence (e.g., Neiderhiser, et al., 2007). Concerns that passive rGE confounds our understanding of intergenerational transmission has inspired designs like the children of twins (COT) design, which can control for passive rGE while also estimating direct environmental effects. Studies using the COT approach have found that the intergenerational transmission of anxiety symptoms, for example, is best explained by direct environmental effects, not passive rGE (Eley et al., 2015). Natural experimental designs that include genetically unrelated parent-child dyads eliminate the effects of passive rGE on associations between parent and child behavior, and therefore provide more direct estimates of environmental influences on child psychopathology that can be targeted in intervention research. The first naturalistic experimental design we present offers unique strengths in this regard: the full parent-offspring adoption design.
