THURSDAY, Jan. 22, 2026 (HealthDay News) -- Among patients with treatment-resistant major depressive disorder (MDD), most of those who achieve benefit with 12 months of adjunctive vagus nerve stimulation (VNS) maintain that benefit at 18 and 24 months, according to a study published in the January issue of the International Journal of Neuropsychopharmacology.Charles R. Conway, M.D., from Washington University in St. Louis, and colleagues characterized depression symptoms, function, and quality of life over 24 months of adjunctive VNS in a prospective, open-label, long-term extension study involving adults with moderate-to-severe MDD with four or more failed antidepressant trials. After receipt of blinded adjunctive VHS for 12 months, 214 patients received open-label, adjunctive VNS for 12 additional months. For depressive symptoms, the durability of benefit achieved at 12 months was assessed at 18 and 24 months.The researchers found that benefit was maintained for most participants with substantial benefit (18- and 24-month median, 78.8 and 79.0 percent, respectively, across five measures) and for participants with at least meaningful benefit at 12 months (18- and 24-month median, 83.1 and 81.3 percent, respectively, across seven measures). Many participants who did not achieve meaningful benefit at 12 months achieved it at 18 and 24 months (median, 30.6 and 37.8 percent, respectively). Changes in psychotropic medications or interventional psychiatric modalities did not account for the strong maintenance of benefit."These results are highly atypical, as most studies of markedly treatment-resistant depression have very poor sustainability of benefit, certainly not at two years," Conway said in a statement. "We're seeing people getting better and staying better."Several authors disclosed ties to biopharmaceutical companies, including LivaNova, which is developing and manufacturing the Vagus Nerve Simulation therapy system and funded the study.Abstract/Full Text.Sign up for our weekly HealthDay newsletter