Vagus nerve stimulation (VNS) for major depressive episodes: one year outcomes

Background: Vagus nerve stimulation has shown promising results in an open, acute phase pilot study of adults in a treatment-resistant major depressive episode. This open, naturalistic follow-up study was conducted to determine whether the initial promising effects were sustained, and whether changes in function would be observed. Methods: Thirty adult outpatients in a treatment-resistant, nonpsychotic major depressive episode received an additional 9 months of vagus nerve stimulation treatment following exit from the 3-month acute study. Changes in psychotropic medications and vagus nerve stimulation stimulus parameters were allowed during this longer-term follow-up study. A priori definitions were used to define response (≥ 50% reduction in baseline Hamilton Rating Scale for Depression total score) and remission (Hamilton Rating Scale for Depression ≤ 10). Results: The response rate was sustained [40% (12/30) to 46% (13/28); p = .317] and the remission rate significantly increased [17% (5/30) to 29% (8/28); p = .045] with an additional 9 months of long-term vagus nerve stimulation treatment after exit from the acute study (1 year total vagus nerve stimulation treatment). Significant improvements in function between acute study exit and the 1-year follow-up assessment as measured by the Medical Outcomes Study Short Form-36 were observed. Conclusions: Longer-term vagus nerve stimulation treatment was associated with sustained symptomatic benefit and sustained or enhanced functional status in this naturalistic follow-up study.