If IL-17 is critical for the immunedysregulation noted in patients with depression, it should be expected that patients with that disorder at early stages of the disease will have well documented increased expression of IL-17, and that over time, serum IL-17 levels as well as the levels of Th17 and other IL-17-producing cells will become significantly amplified, especially in those patients who become more depressed and more obese because of the underlying disease. This evidence concerns the gene IL17A and depressive disorder.