The majority of participants with alcoholism in the COGA data set were male, and the majority of participants with depression were female. Of the sibling pairs added to the data set of alcoholic sibling pairs for the linkage analyses for the AorD phenotype, many consisted of a brother with alcoholism and a sister with depression. Consequently, the gene or genes contributing to these vulnerabilities may have variable expression in men and women. This result is reminiscent of the concept of depressive spectrum disease as postulated by Winokur and colleagues (1971).
