Vagus nerve stimulation (VNS) for treatment-resistant depressions: a multicenter study

Background: Vagus Nerve Stimulation (VNS) delivered by the NeuroCybernetic Prosthesis (NCP) System was examined for its potential antidepressant effects. Methods: Adult outpatients (n = 30) with nonpsychotic, treatment-resistant major depressive (n = 21) or bipolar I (n = 4) or II (n = 5; depressed phase) disorders who had failed at least two robust medication trials in the current major depressive episode (MDE) while on stable medication regimens completed a baseline period followed by NCP System implantation. A 2-week, single-blind recovery period (no stimulation) was followed by 10 weeks of VNS. Results: In the current MDE (median length = 4.7 years), patients had not adequately responded to two (n = 9), three (n = 2), four (n = 6), or five or more (n = 13) robust antidepressant medication trials or electroconvulsive therapy (n = 17). Baseline 28-item Hamilton Depression Rating Scale (HDRS28) scores averaged 38.0. Response rates (≥50% reduction in baseline scores) were 40% for both the HDRS28 and the Clinical Global Impressions—Improvement index (score of 1 or 2) and 50% for the Montgomery–Åsberg Depression Rating Scale. Symptomatic responses (accompanied by substantial functional improvement) have been largely sustained during long-term follow-up to date. Conclusions: These open trial results suggest that VNS has antidepressant effects in treatment-resistant depressions.