All the common disorders considered here have both genetic and environmental risk factors. Another area of exploration in PRS is possible gene-environment interaction, which implies that the effect of the disease PRS would depend on the level of the environmental risk factor. This interaction model contrasts with an additive model, where PRS and environment contribute independently to disease risk. With a positive interaction, the effect of a high PRS would be amplified in the presence of an environmental risk factor (E), putting this subgroup of the population (G+, E+) at particularly high risk of disease. These individuals could form a specific target group for interventions, identified by either PRS or environment, or both.
