The results of this study illustrate what the advocates of GWAS anticipated: as sample sizes get large, thousands of lead SNPs will be identified, and polygenic predictors will attain non-trivial levels of predictive power. However, theoretical projections that failed to consider heterogeneity of effect sizes were optimistic4. Our and others’ findings16,17 suggest that imperfect genetic correlation across cohorts will be the norm for phenotypes that, like EA, are environmentally contingent.
