is an intermediate phenotype for brain-related clinical endpoints, reported genome-wide significant associations using just 322 participants [23]. Furthermore, acute responses to pharmacological perturbations often yield alleles of relatively large effects [24]. Association studies of the response to cisplatin [25], warfarin [26], nortriptyline [27], radiation therapy [28], pegylated interferon and ribavirin [29], and interferon-β [30] have all identified genome-wide significant associations using small samples sizes.
