Deep Brain Stimulation for Treatment Resistant Depression

Inclusion criteria: * Ability to provide written informed consent. * Current Major Depressive Episode (MDE), secondary to either Major Depressive Disorder or Bipolar Disorder (I, II or NOS), diagnosed by structured clinical interview for Diagnostic and Statistical Manual of Mental Disorders-IV-text revision (DSM-IV-TR). * Current MDE at least two years duration OR a history of more than 4 lifetime depressive episodes. * Minimum score at study entry of 20 on the 17-item Hamilton Depression Rating Scale (HDRS-17). * Average pre-operative HDRS-17 score of 20 or greater (averaged over four weekly pre-surgical evaluations during the four weeks prior to surgery) and an average pre-operative HDRS-17 score no more than 30% lower than the baseline screening HDRS-17 score. * A maximum Global Assessment of Functioning of 50. * Treatment-resistant depression defined as: * Failure to respond to a minimum of four different antidepressant treatments, including at least three medications from at least three different classes, evidence-based psychotherapy or electroconvulsive therapy (ECT) administered at adequate doses and duration during the current episode. * Failure or intolerance of an adequate course of electroconvulsive therapy (ECT) during any episode (confirmed by medical records), or refusal of ECT due to a reason considered to be valid by the study psychiatrist. * A patient may remain on psychotropic medications during this study. However, doses must remain stable during the …