Motor threshold parameters do not predict repetitive Transcranial Magnetic Stimulation and intermittent Theta Burst Stimulation outcomes in major depressive disorder.

Background: Repetitive Transcranial Magnetic Stimulation (rTMS) and intermittent Theta Burst Stimulation (iTBS) are non-invasive treatments for major depressive disorder (MDD). While effective, variability in outcomes necessitates identifying predictors of therapeutic response. This study examined whether motor threshold (MT), percentage of motor threshold (%MT), and treatment intensity could predict clinical outcomes in MDD patients undergoing rTMS and iTBS.

Methods: Adult MDD patients treated with NeuroStar rTMS or iTBS at Mayo Clinic from February 2016 to April 2024 were included. MT, %MT, and treatment intensity were recorded. Clinical outcomes were assessed via Patient Health Questionnaire-9 (PHQ-9) score changes, response (PHQ-9 change ≥50 %), remission (PHQ-9 < 5), and a patient-reported outcome (PRO) on treatment helpfulness. Linear and logistic regression models were used to assess predictors of clinical outcomes.

Results: Among 149 patients analyzed (mean age 45.7, 67.8 % female), response rate was 43.0 % and remission rate was 16.8 %. MT and %MT did not significantly correlate with clinical outcomes. Treatment intensity and TMS type did not predict PHQ-9 score changes. Higher treatment intensity was associated with decreased odds of positive PRO responses. Linear regression showed that age and gender significantly predicted PHQ-9 score changes, with older patients and females showing greater improvement. MT was significantly lower in men and with iTBS compared to rTMS.

Conclusion: MT, %MT, and treatment intensity did not reliably predict outcomes. Higher intensity was linked to reduced patient-reported helpfulness, suggesting that patient comfort is crucial. iTBS's lower MT may benefit those needing less stimulation. Future research should identify better predictors to improve TMS outcomes.