First, it is now clear that historical candidate gene association studies for common genetic variation had grossly inadequate statistical power. For example, a candidate gene study of 1,000 cases and 1,000 controls has 0.03% power 22 to detect a genotypic relative risk (GRR) of 1.15 (assuming a log-additive model, lifetime prevalence=0.007, minor allele frequency=0.3, and α=5x10−8). A GRR of 1.15 is large for schizophrenia, and only 10 of 128 SNPs 11 reaching genome-wide significance had GRR > 1.15. When power is so low, the probability that a “significant” finding is a false positive is overwhelming. 23, 24
