Two loci have been reported to harbor common alleles showing genome-wide significant association with both schizophrenia and bipolar disorder13, 16, 23, 24. In addition, several common variants initially displaying genome-wide significant association with one of the disorders have been shown, in subsequent studies, to confer risk of the other31, 32. Investigations considering schizophrenia and bipolar disorder as a single phenotype also support shared risk alleles16, 19, 22, and an overlapping polygenetic component has been described by several studies21, 28. These genetic data are consistent with current epidemiological investigations, which predict shared genetic risk factors for schizophrenia and bipolar disorder33.
