Vagus nerve stimulation (vns) for the treatment of refractory depression

Major depressive disorder represents one of the most prevalent psychiatric disorders with a high socioeconomic impact in the contemporary world, leading to severe impairment of quality of life, chronic functional disability, and an elevated risk of suicidal behavior. Although the current psychopharmacological arsenal and psychotherapeutic interventions offer effective support for a substantial portion of patients, it is estimated that approximately one-third of individuals present treatment-resistant depression (TRD), clinically defined by the absence of a satisfactory response to at least two antidepressant regimens of distinct chemical classes administered in adequate doses and durations. Faced with this scenario of high vulnerability and chronicity, the development of invasive and non-invasive neuromodulation strategies revolutionized the perspectives of interventionist psychiatry, allowing to act directly on dysregulated neural circuits. Given this challenging clinical reality, the objective of this systematic literature review was to analyze the efficacy, safety, neurobiological mechanisms, and tolerability profile of vagus nerve stimulation (VNS) in the management of refractory major depressive disorder, mapping the scientific evidence published in Brazil regarding this technology. The systematic data search was conducted in the SciELO, LILACS, and CAPES Journals Portal databases, identifying clinical trials, prospective cohort studies, and national neuromodulation guidelines. The results demonstrated that chronic treatment with VNS promotes progressive and sustained improvements in depression response and remission rates in the long term, with significant reductions in standardized depression scale scores (such as Hamilton and Montgomery-Åsberg). The mechanisms of action correlate with the modulation of central monoaminergic pathways from the nucleus of the solitary tract and with increased blood flow in the prefrontal cortex and amygdala. It is concluded that vagus nerve stimulation establishes itself as a first-line adjuvant therapeutic strategy that is highly effective and safe for the long-term management of refractory depression, minimizing the morbidity associated with treatment resistance and humanizing the assistance journey of patients in the country.(AU)