In summary, we report results from the first GWAS of a comorbid depressive syndrome/alcohol dependence phenotype. Although we did not identify markers meeting genome-wide significance criteria, nominally significant markers implicate genes that have been previously implicated in alcohol dependence, depression, and other psychiatric disorders. Multiple genes involved in glutamate function are associated with case/control status in our sample, as are other genes involved in neural processes. These results suggest that the comorbid phenotype is influenced by genetic variants somewhat distinct from those influencing alcohol dependence on its own. We feel that these results provide an important step toward understanding the genetic influences on comorbidity between depressive syndrome and alcohol dependence, and more generally toward our understanding of the biological etiology of these disorders.
