The risk variants implicated here confer small risks (odds ratios ~1.10), but the polygenic analysis shows many more susceptibility variants with effects for which our sample is underpowered (Supplementary Table 12). At every stage where samples were added, we found an increase in the number of genome-wide significant loci and enhancement of signals at CACNA1C, ANK3 and ITIH3-ITIH4 when schizophrenia and bipolar disorder were jointly analyzed. Thus, gains in power offset any penalty for increased heterogeneity.
