an order of magnitude larger than the first generation of studies (which typically had under a thousand individuals per sample) will be needed to give some confidence in findings (esp. for interactions involving rare environmental exposures). Studies in the human experimental laboratory, using experimentally controlled stressors or other manipulations, with human subjects selected on the basis of a genetic variant, and perhaps stratified by early environmental exposure, offer some hope of furthering understanding interaction effects with known genetic variants. Yet, even here, likely modest gene effect sizes (c.f. Flint and Munafo, 2007), except for variables such as metabolism, and greater limitations on feasible sample size, will be an important limiting factor.
