MDD case/control status (Figure 1A; full results available in eTable 1) was significantly predicted by the GPRS of psychiatric traits, especially at liberal Pts. Psychiatric GPRS including all independent SNPs (Pt<1) were significantly, although not strongly, correlated (MDD-BIP r=0.22; MDD-SCZ2 r=0.16; BIP-SCZ2 r=0.27; all p<0.0001). When including all three scores in the same model for Pt bins <0.05, <0.01, <0.5 and <1 only GPRS-MDD and GPRS-SCZ2 remained independently associated with MDD. Analyses were repeated including dummy covariates indexing the different genotyping batches and results were essentially unchanged (data not shown). The variance explained on the liability scale for MDD is shown in Figure 2A. GPRS-SCZ2 explained the higher proportion of variance, up to 1.6%, while GPRS-MDD and GPRS-BIP explained up to, respectively, 0.6% and 0.3%. The figure includes also GPRS-SCZ1 derived from the first PGC-GWAS on schizophrenia(42) (~9K cases, ~12K controls) in order to highlight the importance of discovery sample size in GPRS predictive performance(43): GPRS-SCZ1 predicted at best up to 0.5% of the variance on MDD liability. In order to further confirm these findings, we used the equations based
