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 or chronic, treatment-resistant depression is well established. Methods This naturalistic follow-up describes outpatients with nonpsychotic major depressive (n = 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) (n = 95). The 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 Äsberg 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.