While schizophrenia is highly polygenic, DISC1 is an example of a rare schizophrenia-associated gene, which was discovered in a large Scottish family where a balanced chromosomal translocation segregated with schizophrenia and other psychiatric disorders (schizoaffective disorder, bipolar disorder, major depressive disorder; Millar et al., 2000). This evidence concerns the gene DISC1 and bipolar disorder.