• Hamilton Depression Rating Scale (HDRS28) [ Time Frame: 8 weeks after implant surgery ]
  

• 10-item Montgomery-Asberg Depression Rating Scale (MADRS) [ Time Frame: 8 weeks after implant surgery ]
  

Major depressive disorders are the most common of all psychiatric disorders. The World Health Organization estimates that 340 million people worldwide suffer from an episode of major depression each year, accounting for 4.4% of the overall global disease burden. In the United States, about 9.5% or 19 million people are affected by a depressive disorder, with a lifetime risk of about 17% for a major depressive disorder.

While depression can be effectively treated in the majority of patients by medication and psychotherapy, up to 20% of patients fail to respond. Electroconvulsive Therapy (ECT) is effective in approximately 70% of cases where antidepressant medications do not provide sufficient relief of symptoms. However, as many as 20-50% of the people who respond well to a course of ECT relapse within 6 months, therefore, periodic maintenance therapy is often required.

For those patients who are resistant to the therapies noted above, more invasive approaches have been used, including Vagus Nerve Stimulation (VNS) and more recently Deep Brain Stimulation (DBS).

Direct cortical stimulation of the cortex via an implanted device system may provide long lasting benefit with minimal side effects. The current study seeks to assess in a feasibility study the safety and efficacy of stimulating the prefrontal cortex in patients with major depressive disorder.