Although genetic studies indicating an association between MDD and bipolar disorder and Wfs1 have not been consistently confirmed (Ohtsuki et al., 2000; Koido et al., 2005), investigation of Wfs1 carriers and family members has provided strong evidence that Wfs1 mutations can lead to an increased incidence of psychiatric admissions for hospitalization (Swift et al., 1991). The gene discussed is WFS1; the disease is major depressive disorder.