The distinction between additive and interactive effects of genetic and environmental influence is relevant to preventive intervention strategies. Additive effects represent simple arithmetic accumulations of risk, such that mitigation of any single risk factor can only reduce the likelihood of an associated adverse outcome to the extent of that single factor’s contribution. Interactive effects are, in contrast, multiplicative in nature, such that mitigation of a given risk factor simultaneously dismantles risk incurred by any other factor(s) with which it interacts to exert an effect on outcome.
