disorder in first-degree relatives of probands with schizophrenia compared to first-degree relatives of control probands (λSCZ,BPD) of 2.1, which implies a maximum genetic correlation between the disorders of 0.3 (assuming that the disorder risks for schizophrenia and bipolar disorder are both 1% and their heritabilities are 81% and 75%, respectively; Table 1). However, a large-scale Swedish family and adoption study54 estimated the genetic correlation between schizophrenia and bipolar disorder to be +0.60, similar to that found here. Profiling scoring analysis using genome-wide SNPs32 was the first method to clearly demonstrate a genetic relationship based on molecular data, but quantification as a genetic correlation was not reported. The evidence of shared genetic risk factors for schizophrenia and bipolar disorder was strengthened by our analyses of the CNS+ gene set in which we saw a clear enrichment in variants shared by these two disorders.
