The ISC further tested the schizophrenia-derived score against bipolar disorder, to test for a common genetic basis to those conditions. Their strongest result was with the Wellcome Trust Case-Control Consortium (WTCCC) sample of 1829 cases and 2935 controls, obtaining with an inclusion threshold of . Assume similar heritability for bipolar disorder as for schizophrenia [28] and the same genetic variance explained by the markers, estimated above to be 28.7%. Then using equation 5, the study had 80% power at nominal significance if the correlation is 28% between genetic effects on schizophrenia and bipolar disorder. Using equation 6, the estimated correlation given the observed association statistic is 70.6% (95%CI: 51.3%–89.7%) assuming that all SNPs have effects with explained variance 28.7% in both samples. If 99% of SNPs are assumed null, the estimated correlation reduces to 66.2% (95%CI: 48.1%–84.1%).
