Deep Brain Stimulation: A promising therapeutic approach to the treatment of severe depressed patients. Current evidences and intrinsic mechanisms.

Abstract

Major depressive disorder represents one of the most severe disabling disorders which affects around 4.7% in the worldwide population. Many patients suffering this neuropsychiatric illness are successfully treated with various treatments including antidepressant drugs and psychotherapy but also physical measures (electroconvulsive therapy, repetitive transcranial magnetic stimulation, vagal nerve stimulation). Despite the different treatment approaches available, unfortunately 30–40% of the patients fail to respond to most first­line treatments, and between 5 and 10% do not respond to conventional therapy. Thus, a considerable number of patients have a poor outcome and unfortunately fail to reach sustained remission. These data highlight the need to find new therapeutic approaches especially focused on refractory patients. In this context, deep brain stimulation (DBS) emerges as an innovative physical treatment for refractory depressed patients. DBS has been successfully used for years in some neurological disorders such as Parkinson’s disease. Currently, in addition to its use in treating depression, DBS is also tested in other psychiatric illness such as obsessive–compulsive disorder. Most studies on DBS have focused on efficiency and efficacy, or improvement in the technique, and a few were devoted to understanding the intrinsic responsible mechanisms. To understand the molecular mechanism of the action of DBS is currently considered as crucial, not only in order to understand its efficacy but also to propose new mechanisms of action for future antidepressant approaches. The aim of this chapter is to review the foundations, the efficacy, and the efficiency of DBS in depression, and to provide a view about the intrinsic mechanisms of action described until now. In addition, a perspective of future developments will be discussed.