As efforts to characterize how polygenic predispositions influence complex behavioral outcomes increase in popularity [16], we believe that environmentally-informed designs such as sibling comparisons will become a particularly useful tool to illuminate the “chains of risk” from genotype to phenotype. For example, sibling differences can be elaborated upon to include examination of how subtle differences in polygenic loading between siblings impact individual differences or selection into particular environments. In turn, these mediating phenotypes may be particularly actionable targets for prevention and intervention efforts.
