To benchmark the estimates of genetic sharing across disorders, we estimated sharing between data subsets for the same disorder. We split the data for each disorder into two or three independent sets and estimated hSNP2 values for each subset and the SNP-based coher-itability between each pair of subsets within a disorder (Fig. 3a and Supplementary Table 5). The estimates of hSNP2 from the data subsets were typically higher than the hSNP2 estimate from the combined sample; we note that published estimates from individual cohorts of bipolar disorder18, major depressive disorder36 and ASD37 were also higher. Because both traits in these data subset bivariate analyses are for the same disorder, the SNP-based coheritability is also an estimate of hSNP2 for the disorder, but these estimates were generally lower than the estimates of SNP-based heritability from individual data subsets. These results generated SNP-based correlations that were less than 1, sometimes significantly so (Supplementary Table 5). The SNP-based correlation between schizophrenia and bipolar disorder (0.68, 0.04 s.e.) was of comparable magnitude to the SNP-based correlations between bipolar disorder data sets (0.63, 0.11 s.e.;
