To the extent that resources are available, we encourage a long-term view, avoiding the well-known pattern of initial exuberance followed by disillusionment. The logic of GWAS has been clear for over ten years. (23) Results have been remarkably consistent with expectations, in the sense that common SNP associations have been discovered for many common disorders, particularly those that have been studied with larger sample sizes. It is true that initial GWAS results have explained only a small part of the etiologic variance for each disease, and it seems certain that studies of CNVs and rare SNPs will also be critical in elucidating disease mechanisms. But it is likely that common SNPs explain a larger portion of the variance than can be determined with existing sample sizes, with many common SNPs, each with small effects, contributing collectively to a major portion of genetic risk (24). As the number of associations increases, the biological pathways underlying risk for each disease become more clear. GWAS methods should be applied systematically to major psychiatric disorders in large samples.
