Effects of 12 months of vagus nerve stimulation in treatment-resistant depression: A naturalistic study

Background: The need for effective, long-term treatment for recurrent for chronic, treatment-assitant depression is well established. Methods. This naturalistic follow-up describes outpatients with nonpsychotic major depressive (h = 185) or bipolar (I or II) disorder, depressed phase (n = 20) who initially received 10 weeks of active (n = 110) or sham vagus nerve stimulation (VNS) (it = 95). 7-be initial active group received another 9 months, while the initial sham group received 12 months of VNS. Participants received antidepressant treatments and VNS, both of which could be adjusted. Results: The primary analysis (repeated measures linear regression) revealed a significant reduction in 24-item Hamilton Rating Scale for Depression (HRSD24) scores (average improvement, .45 points [SE =.05] per month (p < .001). At exit, HRSD24 response rate was 27.2% (55/202); remission rate (HRSD24 <= 9) was 15.8% (32/202). Montgomery Asberg Depression Rating Scale (28.2% [57/202]) and Clinical Global Impression-Improvement (34.0% [68/200]) showed similar response rates. Voice alteration, dyspnea, and neck pain were the most frequently reported adverse events. Conclusions. These 1-year open trial data found VNS to be well tolerated, suggesting a potential long-term, growing benefit in treatment-resistant depression, albeit in the context of changes in depression treatments. Comparative long-term data are needed to determine whether these benefits can be attributed to VNS.