individuals with self-reported European ancestry confirmed by genome-wide principal components, as described previously (Miller et al., 2012). The GEDI sample was selected in an attempt to maximize power to detect associations with measures of alcohol use and externalizing psychopathology (see details in online supporting information). BRIDGES samples had been selected from the MCTFR cohorts to serve as additional controls in a case-control genetic association study of bipolar disorder. As such, these samples happened to have been screened for major forms of psychopathology to be included in the BRIDGES study. BRIDGES selection criteria were at least 23 years of age; no history of mania, major depression, or alcohol dependence; and no first-degree relative with a history of bipolar disorder or major depressive disorder. In addition, the samples were matched for northern European ancestry to other BRIDGES bipolar cases using genetic principal components. Not all of these GEDI- and BRIDGES-selected individuals participated in the psychophysiology lab.
