It is important to note that even the highest priority candidate variants may be difficult to study. If the follow-up study involves association analysis of the candidate variant with another complex (endo) phenotype samples of over 1000 unrelated individuals will be required to obtain sufficient power (see Table 3). Molecular work, for example studies of gene expression or cellular processes affected by a candidate variant, may result in much larger expected effect sizes and require a fraction of the observations as for complex phenotypes. In either case recent success in GWAS will only spur additional focused analyses of candidate genes and genomic regions, except now we will know that these regions harbor genetic variation that actually affect disorder risk in humans, a critical advance in genetic research.
