Stress vulnerability effects on gene-environment correlation over time

People select environments nonrandomly, in part because people match to environments based on their enduring genetic predispositions and existing environmental access. Previous research has demonstrated how person-environment... [ view full abstract ]

People select environments nonrandomly, in part because people match to environments based on their enduring genetic predispositions and existing environmental access. Previous research has demonstrated how person-environment matching processes can be parameterized in longitudinal twin studies (Beam CR, Turkheimer E. Dev Psychopathol 2013;25:7–16; de Kort JM, Dolan C V, Boomsma DI. Neth J Psychol 2012;67:81–90). These studies have shown that gene-environment correlation can be estimated to quantify the strength of the match between people and their environments over time. Using a reciprocal effects framework (Bronfenbrenner U, Ceci SJ. Psychol Rev 1994;101:568–86; Dickens WT, Flynn JR. Psychol Rev 2001;108:346–69), people actively seek out and are reinforced by their subsequent environmental exposure based on their genetic and environmentally influenced behavior. One statistical consequence of this process is that gene-environment correlation increases over time. Yet, whether stress conditions affect the degree to which people pursue environments that are a stronger match for them has not been explored. In this study, we test the hypothesis that person-environment matching is stronger in high stress vulnerability periods compared to low stress vulnerability periods.

We present a longitudinal twin study of positive affect (PA) and negative affect (NA) using a sample of normal menstrual cycling MZ and DZ female twin pairs from the Michigan State University Twin Registry (Klump et al.,Twin Res 2006, 9:971–977) across 25 days of the menstrual cycle (MZ pairs = 250; DZ pairs = 191). We used a genetic simplex model that allows for estimation of gene-environment correlation parameters over 25 days. Specifically, the parameter allows for the accrual of within-family gene-environment correlation (rGE) in DZ twins, which is used to test whether gene-environment correlation is stronger during high stress vulnerability periods versus low stress vulnerable periods. High stress vulnerability period was defined as the second half (luteal phase) of the menstrual cycle while low stress vulnerability was defined as the first half (follicular phase) of the cycle. We observed no systematic rGE pattern during the first-half of these twins’ menstrual cycles whereas rGE for both PA and NA increased steadily during the luteal phase. Additionally, we note that heritability of PA and NA increased slightly during this same period. Persistence of nonshared environmental effects were not observed. We conclude with a discussion about why gene-environment correlation is stronger during high stress vulnerability periods compared to low stress vulnerability periods.