Vagus nerve stimulation (VNS (TM)) for treatment-resistant depression: Efficacy, side effects, and predictors of outcome

This open pilot study of vagus nerve stimulation (VNS (TM)) in 60 patients with treatment-resistant major depressive episodes (MDEs) aimed to: 1) defi ne the response rate; 2) determine the profile of side effects; and, most i mportantly; 3) establish predictors of clinical outcome. Participants were outpatients with nonatypical, nonpsychotic, major depressive or bipolar dis order who had not responded to at least two medication trials from differen t antidepressant classes in the current MDE. While on stable medication reg imens, the patients completed a baseline period followed by device implanta tion. A 2-week, single blind, recovery period (no stimulation) was followed by 10 weeks of VNS. Of 59 completers (one patient improved during the reco very period), the response rate was 30.5% for the primary HRSD28 measure, 3 4.0% for the Montgomery-Asberg Depression Rating Scale (MADRAS), and 37.3% for the Clinical Global Impression-Improvement Score (CGI-1 of 1 or 2). The most common side effect was voice alteration or hoarseness, 55.0% (33/60), which was generally mild and related to output current intensity. History of treatment resistance was predictive of VNS outcome. Patients who had nev er received ECT (lifetime) were 3.9 times more likely to respond. Of the 13 patients who had not responded to more than seven adequate antidepressant trials in the current MDE, none responded, compared to 39.1% of the remaini ng 46 patients (p = .0057), Thus, VNS appears to be most effective in patie nts with low to moderate, but not extreme, antidepressant resistance. Evide nce concerning VNS' long-term therapeutic bene fits and tolerability will b e critical in determining its role in treatment-resistant depression. (C) 2 001 American College of Neuropsychopharmacology. Published by Elsevier Scie nce Inc.