An important corollary of the question “Which gene?” is “What is the mechanism of GxE?” (Shanahan & Hofer, 2005). The strong theoretical grounding of Schlomer et al.’s article is characteristic of family research and thus illustrates an approach that is much needed in cGxE research. The authors make specific hypotheses about the mechanisms linking interparental relationship characteristics and adolescent internalizing and how these associations may differ as a function of a (purported) differential susceptibility locus, DRD4. This theoretically informed approach is much richer than the typical cGxE study, in which the theory regarding the significance of the environment and hypotheses about the mechanism of the GxE effect are often not fully developed. We return to the strengths of this theory-driven approach, and the novel contributions that family researchers can make to this area, in our recommendations below.
