Berlin Deep Brain Stimulation Depression Study

Inclusion Criteria: * patient is diagnosed with a severe major depressive episode * patient is in a chronic current MDE and/or has had a history of recurrent MDEs * patient has not had an acceptable clinical response due to failure with at least three antidepressant treatments during the current episode. * patient has a score \> 20 on the HAMD24 * patient is stable on current psychotropic medication for at least 6 weeks * patient is \>25 and \<80 years * Global Assessment of Function (GAF) score of \< 45 Exclusion Criteria: * Atypical Depression (according to DSM IV) * Other relevant psychiatric axis I or axis II diseases * Relevant neurological diseases * Relevant cardiac or pulmonary diseases with enhances anaesthesiological risk (ASA Score \> 3) * Patient is currently enrolled in another investigational study not associated with the current study * Patient has a history of, or evidence of, significant brain malformation or significant head injury * Patient is likely to require a whole body MRI after implantation