Recapturing the Initial Clinical Benefit of TMS in a Major Depressive Episode: a Retrospective Analysis in a Veteran Cohort

Background: Repetitive transcranial magnetic stimulation (TMS) is now widely accepted as an effective non-pharmacologic treatment for treatment-resistant depression. However, whether repeated acute TMS courses can recapture the antidepressant effects of the initial acute course is still an open question, especially in the Veteran population. We present here a retrospective analysis of a specialty clinic within the Veteran Affairs Hospital System to help address this question. Aims: Following an acute treatment course of TMS, we sought to determine the treatment response of a subsequent TMS course. We hypothesized that those who responded to an initial acute TMS course would respond in a similar manner to a subsequent treatment course. Methods: 116 cases referred for evaluation for TMS between September 2017 to April 2021 were reviewed. 63 Veterans completed at least one acute course of TMS and 12 completed at least two courses and met inclusion criteria for this review. Symptoms were evaluated via self-reported scales at baseline and weekly throughout treatment. Clinical response to subsequent treatment (>50% symptom reduction as measured by the PHQ-9) was compared to initial treatment response. Results: Of the initial treatment responders (n = 6), all six responded to a second acute course, with an 85.3% symptom reduction. Of the initial treatment non-responders (n = 6), three responded to a second acute course. Exploratory regression analysis predicted change in depression symptoms (PHQ-9) during a second TMS course using initial treatment response, time into treatment, and baseline symptom severity. Together, these factors explained 72% of the variance. No adverse events were reported in those who completed a second course, and the Veterans tolerated the treatment well. Conclusions: Our findings support the growing understanding that a second acute TMS treatment course for treatment-resistant depression is safe, well-tolerated, and effective in initial responders and some non-responders. Despite multiple confounders in a naturalistic setting, robust initial treatment response was sustained in a second acute course. Low power limits generalizability, and larger powered, prospective studies are needed.