Deep Brain Stimulation in Treatment Refractory Depression

This study aims to investigate the effect of deep brain stimulation (DBS)in major depressive disorder (MDD). After implantation of the DBS system, the effects of deep brain stimulation in ITP and CI/BNST will be evaluated. The design of the study consists of two consecutive crossover phases, interspaced with 2 optimalisation episodes. After a period of optimalisation of CI/BNST stimulation parameters, patients will be randomised in two groups. Half of the group of patients will receive stimulation in CI/BNST. The other half will not. After one week both groups will switch conditions during a period of one week. This will give an idea of the effects of stimulation in CI/BNST on the outcome measures. Outcome measures will be evaluated after each week. After this first crossover patients will continue to an optimalisation phase of ITP stimulation parameters. A second crossover will then follow. The effects of ITP stimulation, CI/BNST stimulation and no stimulation will be compared. In this phase patients will again be randomised to receive one of the six possible combinations of three consecutive periods of two months for the three different stimulation conditions (ITP stimulation, CI/BNST stimulation and no stimulation). Evaluations of outcome measures will be performed by blinded evaluators. This design will limit the duration of periods in which these severly ill patients are not stimulated.