Depression is a common illness worldwide, with an estimated 3.8% of the population affected; by 2030 it will be the leading cause of disease burden globally. Depression has been associated with more prolonged hospital stays, increased physical distress, poorer treatment compliance, lower quality of life, and increased desire for hastened death. A meta-analysis revealed that minor or major depression increases the rate of mortality by up to 39%; in addition, patients displaying even a few depressive symptoms may be at a 25% increased risk of mortality. The monoamine hypothesis is the most extensively studied etiologic theory of depression and virtually all available antidepressants act, at least in part, by increasing monoaminergic transmission.