Patients with a clinical diagnosis of severe depression including suicidal ideation; Prior neurosurgical procedure; Past history of epilepsy or family history of epilepsy; Previous head injury; Metal located in the head, i.e. shrapnel, surgical clips, or fragments from welding; Signs of increased intracranial pressure; Stroke; Chronic treatment with epileptogenic medications; Abnormal neurological examination other than as signs of the condition studied in the present protocol; Implanted pacemaker; Medication pump; Vagal stimulator; Deep brain stimulator; Transcutaneous electrical stimulation (TENS) unit and ventriculo-peritoneal shunt; Pregnancy; Other chronic medical conditions and history of substance abuse; History of medical and surgical therapies for pain within 3 months.