IL-17, a pro-inflammatory cytokine, is a member of the cytokine family comprising IL-17A, IL-17B, IL-17C, IL-17D, IL-17E (IL-25) and IL-17F [22,23,24] and it was found before, to be elevated in the serum of patients suffering from depression. The gene discussed is IL17A; the disease is depressive symptom measurement.