The effects of vagus nerve stimulation on sleep EEG in depression: A preliminary report

Objective: The present study evaluated the effects of vagus nerve stimulation (VNS) on sleep in seven treatment-resistant depressed outpatients. Methods: Sleep studies were conducted in the laboratory at baseline and 10-12 weeks after VNS implantation while the concomitant psychotropic medication regimen was unchanged. Standard sleep macroarchitecture based on visual stage and assessment of ultradian sleep electroencephalographic (EEG) rhythms were measured on all nights. Results: An overall significant treatment effect on sleep macroarchitecture was obtained by MANOVA. Decreased awake time, decreased Stage 1 sleep and increased Stage 2 sleep were evident post-VNS, although univariate analyses did not reach significance. In addition, the strength or amplitude of ultradian sleep EEG rhythms more than doubled on VNS and was restored to within normal range. Conclusion: VNS improved the clinical symptoms of depression and sleep architecture. Results suggest that treatment-resistant depressed patients have dampened sleep EEG rhythms that are restored to near-normal amplitudes with VNS treatment.