Repetitive transcranial magnetic stimulation shows longitudinal improvements in memory in patients with treatment-resistant depression

Abstract

Background Cognitive dysfunction (CD) is a commonly reported symptom of major depressive disorder (MDD). Patients with treatment-resistant depression (TRD) tend to experience greater rates of CD; however, treatment options are limited. Repetitive transcranial magnetic stimulation (rTMS) is effective in treating affective symptoms in patients with TRD, but its potential effect on CD in TRD has not been established. Objectives This study sought to establish the potential cognitive benefits of rTMS in patients with TRD. Materials and methods This study used data from a noninferiority clinical trial investigating two excitatory rTMS protocols to the left dorsolateral prefrontal cortex in unipolar outpatients with TRD. Cognitive testing was performed at baseline and three months posttreatment in 47 patients and a demographically matched cohort of 22 healthy volunteers. Changes in cognitive performance from baseline to posttreatment were assessed using repeated-measures analysis of variance, using both normative and individualized cognitive scoring methods. Results Patients with baseline neurocognitive dysfunction showed significant changes in verbal memory at three months posttreatment when using individualized cognitive scoring. Furthermore, improvement in verbal memory within this subset was associated with improvements in affective symptoms. Limitations This analysis was performed on a relatively small sample of patients with TRD who were not prescreened for CD and did not include a clinical comparator group. Conclusions rTMS may be associated with improvements in verbal memory in patients with TRD who present with global CD and who are clinical responders to the treatment. These findings warrant replication in a larger sample as well as further investigations into the neural mechanisms of cognitive improvement after rTMS.