The Schizophrenia Psychiatric Genome-Wide Association Study Consortium (PGC) 
highlighted 81 single-nucleotide polymorphisms (SNPs) with moderate evidence for 
association to schizophrenia. After follow-up in independent samples, seven loci 
attained genome-wide significance (GWS), but multi-locus tests suggested some 
SNPs that did not do so represented true associations. We tested 78 of the 81 
SNPs in 2640 individuals with a clinical diagnosis of schizophrenia attending a 
clozapine clinic (CLOZUK), 2504 cases with a research diagnosis of bipolar 
disorder, and 2878 controls. In CLOZUK, we obtained significant replication to 
the PGC-associated allele for no fewer than 37 (47%) of the SNPs, including many 
prior GWS major histocompatibility complex (MHC) SNPs as well as 3/6 non-MHC 
SNPs for which we had data that were reported as GWS by the PGC. After combining 
the new schizophrenia data with those of the PGC, variants at three loci 
(ITIH3/4, CACNA1C and SDCCAG8) that had not previously been GWS in schizophrenia 
attained that level of support. In bipolar disorder, we also obtained 
significant evidence for association for 21% of the alleles that had been 
associated with schizophrenia in the PGC. Our study independently confirms 
association to three loci previously reported to be GWS in schizophrenia, and 
identifies the first GWS evidence in schizophrenia for a further three loci. 
Given the number of independent replications and the power of our sample, we 
estimate 98% (confidence interval (CI) 78-100%) of the original set of 78 SNPs 
represent true associations. We also provide strong evidence for overlap in 
genetic risk between schizophrenia and bipolar disorder.