For the analyses presented here, participants were diagnosed with alcoholism (ALC) if they met the diagnostic criteria for alcohol dependence specified in the Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised (DSM–III–R) (American Psychiatric Association [APA] 1987) as well as the criteria for “definite alcoholism” established by Feighner and colleagues (1972). Participants were diagnosed with depression (DEP) if they met the DSM–III–R criteria for major depressive disorder or if they had “depressive syndrome.” (Subjects were classified as having depressive syndrome if they met all the criteria for major depressive disorder, except that the depression could have been caused by alcohol or other drug use or another illness.) Participants with both ALC and DEP were included in the phenotype “alcoholism and depression” (AAD). People meeting the criteria for either ALC or DEP were combined into a phenotype called “alcoholism or depression” (AorD). Separate analyses were conducted for participants with the DEP phenotype—that is, with depression or depressive syndrome (which can occur in both alcoholics and nonalcoholics). The COGA researchers performed statistical analyses of differences in the prevalence of alcoholism
