Major depressive disorder (MDD) severely limits a person’s psychosocial functioning and reduces quality of life. According to world statistics, about 3.8 percent of the population, or about 280 million people, suffer from depression. Approximately one-third of patients with MDD have treatment-resistant depression (TRD). Meanwhile, Vagus Nerve Stimulation (VNS) therapy was approved by the US Food and Drug Administration and received CE marking in Europe for the treatment of chronic or recurrent depression in the early 2000s. The aim of this analysis is to determine the impact of VNS use in the treatment of TRD.

A comprehensive literature search was performed in MEDLINE/PubMed and Google Scholar databases in order to estimate the clinical effectiveness of neurostimulator implantation for treatment of TRD. The main assessment methods were the Hamilton Rating Scale for Depression, the Montgomery-Asberg Depression Rating Scale and the Beck Depression Inventory.

In total, 6 systematic reviews with meta-analyses on the effectiveness of VNS in TRD were studied. The identified meta-analyses did not report any statistically significant differences in treatment outcomes favoring VNS compared to placebo and treatment as usual (TAU). However, the results of two studies demonstrate its positive clinical effect in the form of additional treatment to the TAU with longer follow-up period. An improvement in the clinical response is observed on average after 12 months as a decrease of about 50 percent in the initial estimates of depression.

Despite the lack of clinical evidence of the benefits of treating depression, VNS therapy should be used as a standard adjunct treatment to antidepressants or other treatments for people with TRD. Many studies tend to suggest that the efficacy and safety of VNC in depression is still unclear, and additional further research is still needed to establish clinically significant effects.