The discoveries from these large GWAS studies are robust and replicable, and for certain phenotypes, the amount of variance explained in total from genome-wide significant SNPs is becoming non-trivial (e.g., 60% for type-I diabetes; 10% for height; Visscher et al., 2012). In the area of psychiatric genetics, studies of the genetic basis of schizophrenia are currently enjoying the most success, where sample sizes on the order of >13,800 cases and >18,000 controls have now been accumulated, leading to the detection of >3500 loci in 12 genomic regions that contribute to the disorder (Ripke et al., 2013). It is noteworthy, however, that even with such impressive sample sizes, the Ripke et al. (2013) landmark study (which is undergoing a further growth in sample size) acknowledged the lack of power to detect genotype relative risks less than 1.1.
