An antidepressant is a psychiatric medication used to alleviate mood disorders, such as major depression and dysthymia. These medications are among those most commonly prescribed by psychiatrists and other physicians, and their effectiveness and adverse effects are the subject of many studies and competing claims. This book presents topical data on antidepressants including neuroplasticity hypothesis and depression; monitoring antidepressant therapy using heart rate variability; the role of antidepressant pharmacotherapy in the prevention of suicide; a new approach to treatment strategy of depressive disorders based on modulation of PEP activity with synthetic inhibitors and understanding the pathogenesis of depression and the mechanism of action of clinically effective antidepressants.