Genetic correlation analyses supported a high consistency in the phenotype across cohorts (rg ranging from 0.82 to 0.93, Supplementary Table 5), and between iPSYCH1 and iPSYCH2 (rg = 0.97; s.e. = 0.06). None of the genetic correlations were significantly different from 1. LD score regression analysis found an intercept of 1.04 (s.e. = 0.009) and ratio of 0.092 (s.e. = 0.02), the latter indicating that around 90% of the deviation from null, in the distribution of the test statistics, reflects polygenicity (QQ-plot shown in Supplementary Fig. 2). The SNP heritability (h2SNP) was estimated to 0.14 (s.e. = 0.01), which is lower than the previously reported h2SNP of 0.2214. The h2SNP for iPSYCH (h2SNP = 0.23; s.e. = 0.01) was in line with the previous finding, but lower h2SNP was observed for PGC (h2SNP = 0.12; s.e. = 0.03) and deCODE (h2SNP = 0.08; s.e. = 0.014). The difference in h2SNP was not caused by different sex distributions across cohorts as there were no significant differences in h2SNP between males and females in the iPSYCH and deCODE cohorts (Supplementary Table 5). Between-cohort heterogeneity in h2SNP is not unusual and has been observed in other diagnoses such as major depressive disorder22.
