Estimating the proportion of variation in susceptibility to schizophrenia captured by common SNPs

Schizophrenia is a complex disorder caused by both genetic and environmental factors. Using 9,087 cases, 12,171 controls and 915,354 imputed SNPs from the Psychiatric GWA Consortium for schizophrenia (PGC-SCZ) we estimate that 23% (s.e. 1%) of variation in liability to schizophrenia is captured by SNPs. We show that an important proportion of this variation must be due to common causal variants, that the variance explained by each chromosome is linearly related to its length (r = 0.89, p = 2.6 × 10(−8)), that the genetic basis of schizophrenia is the same in males and females, and that a disproportionate proportion of variation is attributable to a set of 2725 genes expressed in the central nervous system (CNS) (p = 7.6 ×10(−8)). These results are consistent with a polygenic genetic architecture and imply more individual SNP associations will be detected for this disease as sample size increases.