Background Although there is a clear phenotypic relationship between the quality of the inter-parental or marital relationship and child conduct problems (CP), the etiology of this association is as yet unclear. One possibility is that this association takes the form of a genotype-environment interaction (GxE), whereby the quality of the inter-parental relationship acts to moderate the etiology of child CP. The current study sought to evaluate this possibility. Methods We examined multiple measures and informant-reports of the quality of the inter-parental relationship in a sample of more than 700 child twin families from the Michigan State University Twin Registry (MSUTR). Analyses consisted of a series of latent GxE models. Results The ‘no moderation’ model provided the best fit to the data in nearly all cases, findings that collectively provide strong evidence against the possibility that the etiology of CP is moderated by the quality of the interparental relationship. Conclusions Such findings suggest that, contrary to implicit (and sometimes explicit) assumptions in the field, it is not the case that every environmental risk (or protective) factor exacerbates (or suppresses) genetic influences on CP. Future research should seek to delineate the specific environmental experiences that do serve as etiologic moderators of CP, and to clarify how this gene-environment interplay might change over the course of development.

The current study evaluated associations among externalizing psychopathology, personality, and relationship quality in a sample of 794 couples. Personality and psychopathology were assessed using dimensional measures, and relationship attributes were assessed with both self-report and observer reports of videotaped interactions. Results were consistent with prior work (i.e., Humbad, Donnellan, Iacono, & Burt, 2010) such that greater externalizing psychopathology remained a significant predictor of lower relationship adjustment, while controlling for personality traits. Importantly, dimensional measures of externalizing psychopathology showed stronger associations with relationship adjustment when compared to symptom count measures used in Humbad et al. (2010). These results highlight the importance of replication and extension studies, the usefulness of dimensional measures of psychopathology, and the value of multiple methods of assessment to increase confidence in the robustness of associations between pathological attributes of personality and features of romantic relationships.

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