This lack of positive results from GWAS is most likely due to low statistical power to detect small effects(Visscher, Brown, McCarthy, & Yang, 2012). For example, recent work of the Schizophrenia Working Group of the Psychiatric Genomics Consortium (PGC) illustrated the direct relationship between sample size and success in detecting genetic variants. Their latest GWAS, including 36,989 cases and 113,075 controls, identified 108 genome-wide significant independent genomic loci, providing new insights in the pathology of schizophrenia(Schizophrenia Working Group of the Psychiatric Genomics Consortium, 2014), while earlier studies (2009, 2013) detected 1 and 13 genome-wide significant SNPs, with total sample sizes of 6909 (Ncases=3322) and 59,318 (Ncases=21,246), respectively(Purcell et al., 2009; Ripke et al., 2013).
