The underrepresentation of Blacks in genetic studies of major depression is particularly important because differences in rates of disorders suggest possible genetic and/or social differences in causes. Compared with Whites, Blacks suffer higher rates of many serious physical illnesses such as hypertension and diabetes, (Williams, 1999), but paradoxically have lower rates of major depression (Breslau et al., 2006; Williams & Earl, 2007). Several community-based epidemiological studies in the United States over the last 20 years show similar patterns of racial/ethnic differences, with Blacks reporting lower rates of major depression than Whites (Somervile et al., 1989; Kessler et al., 1994; Jackson et al., 2004; Hasin et al., 2005). Whether the difference is an artifact of sampling or reporting, is unclear. Assuming that the difference is nonartifactual, the mechanisms responsible for this persistent finding, genetic, environmental, or a combination of both, are poorly understood. Although preliminary research has suggested possible genetic differences between Blacks and Whites with regard to depression risk and the response to pharmacological treatments of depression (Lotrich et al., 1997; Gelertner et al., 1998; Gelertner et al., 1999; Lotrich
