Major depression and anxiety are common psychiatric illnesses whose etiology remains incompletely understood. This review highlights progress in understanding the etiology of these illnesses through genetic strategies and looks forward to their impact on geriatric psychiatry. We briefly address three broad domains of progress, namely 1) genetic approaches to etiology, including linkage and association studies, pharmacogenetics ("personalized medicine"), and gene x environment interactions; 2) mechanisms of thyroid and testosterone action via nuclear receptors, given these hormones' status as possible augmenters of antidepressants; and 3) the role of the neuroimmune system as a contributor to the stress response. Genetic strategies offer one path for converting correlational findings into causal pathways while complementing studies of a gene's function at the molecular, cellular, network, and whole-organismal levels. Neuroendocrine supplementation (thyroid and testosterone) has a long history and tradition. A molecular understanding of nuclear receptor pathways and their coactivators, the mediator complex proteins, provides a rationale for improved targeting of hormonal action in a tissue-selective manner, yielding drugs with improved safety and efficacy. Neural-immune interactions in psychiatric illness remain tantalizing topics. Research suggests that cytokine pathways may contribute to the maintenance or susceptibility to stress, anxiety, and depressive disorders. The reciprocal and recursive interactions among basic science, drug discovery, and clinical science will continue to provide hopeful themes for improving the lives of patients with treatment-refractive psychiatric illness.