With a few exceptions, Blacks or African Americans are underrepresented in genetic studies of psychiatric disorders. Non-Hispanic Whites have typically comprised 90% or more of samples in U.S.-based family history studies (Gershon et al., 1982; Sullivan, Neale, & Kendler, 2000; Tsuang, Winokur, & Crowe, 1980; Weissman, Gershon et al., 1984; Weissman et al., 1986), adoption and/ or twin studies (Cadoret, O’Gorman, Heywood, & Troughton, 1985; Kendler, 2001; Kendler & Prescott, 1999; 2000; Lyons et al., 1998; Wender et al., 1986), and genetic linkage studies (Camp et al., 2005; Holmans et al., 2007; Levinson et al., 2007; McGuffin et al., 2005; Zubenko et al., 2003). On the other hand, non-Hispanic Blacks, who approximated 11–13% of the U.S. population between 1980 and 2006 (U.S. Census Bureau, 1980; 1990; 2006), have made up 0% to less than 5% of the sample in such studies. Furthermore, among Blacks, there are no within-group formal family history studies of major depression.
