The Role of Brain Derived Neurotrophic Factor Polymorphism in Transcranial Magnetic Stimulation Response for Major Depressive Disorder.

Objectives: Repetitive transcranial magnetic stimulation (rTMS) is a safe and effective therapy for treatment-resistant depression (TRD). A crucial next step in improving rTMS therapy is to identify response predictors to inform patient selection criteria. Brain-derived neurotrophic factor (BDNF) exerts influence over TRD treatment modalities. BDNF polymorphism, Val66Met, has shown altered cortical plasticity after single-session rTMS in healthy subjects and clinical response in noninvasive brain stimulation methods in major depressive disorder, stroke, Alzheimer's, and cerebral palsy. We sought to evaluate the effect of this BDNF polymorphism on clinical response in a standard course of rTMS therapy for TRD.

Methods: In this naturalistic study, 75 patients with TRD completed a standard course of rTMS with weekly clinical assessments via the Inventory of Depressive Symptomatology Self-Report (IDS-SR). BDNF polymorphisms were retrospectively compared in respect to treatment response and remission, baseline and final scores, percent change scores, and scores across the 6-week treatment course.

Results: As expected, rTMS significantly decreased depressive symptoms as measured by IDS-SR scores. No difference was found in baseline, final, or percent change IDS-SR scores between polymorphism types. There was no difference between polymorphisms in IDS-SR scores across the treatment course. Response and remission rates did not differ between genotypes.

Conclusions: In contrast to previous research highlighting differential response between BDNF polymorphisms to motor plasticity and clinical rTMS outcomes, our data suggest that BDNF polymorphism status may not influence the response to a standard course of 10-Hz rTMS for major depressive disorder. Differences in TMS protocol, target, or BDNF serum levels may underlie our results.