Higher neutrophil-lymphocyte ratio predicts poor response to repetetive transcranial magnetic stimulation(rTMS) in treatment resistant depression

Repetitive transcranial magnetic stimulation (rTMS) has emerged as a noninvasive therapy for treatment resistant depression (TRD). The results of studies on the mechanism of rTMS and the predictive parameters for determining which patients will respond to rTMS are inconclusive. This study aims to investigate the relationship between pre-treatment systemic inflammatory markers and the response to rTMS in TRD patients. We retrospectively reviewed 86 patients with TRD who received 10 Hz rTMS to the left dorsolateral prefrontal cortex (DLPFC) at Gazi University between June 2017 and June 2023. Inflammatory markers, including neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), and systemic immune-inflammatory index (SII), were evaluated. Treatment response was assessed using the Montgomery-Åsberg Depression Rating Scale (MADRS), with a ≥50% reduction in MADRS score and a score ≤8 at the end of treatment considered as a positive response. Patients divided in to two groups accoording to rTMS response. 53 patients were responders and 33 patients were non-responders. Significant differences in inflammatory parameters were observed, with non-responders showing higher NLR (p=0.001), PLR (p=0.008), and SII (p=0.002) values. Logistic regression analysis revealed that higher NLR was significantly associated with a poorer response to rTMS (OR=0.373, p=0.022). Additionally, early improvement in MADRS score in the first week predicted overall treatment outcome (OR=1.070, p<0.001). Our findings suggest that systemic inflammation plays a role in TRD and that higher pre-treatment NLR is associated with a poorer response to rTMS. Largerscale studies are needed to further understand the mechanisms and improve treatment strategies for TRD patients.