A pragmatic randomized controlled trial exploring the relationship between pulse number and response to repetitive transcranial magnetic stimulation treatment in depression

Background: Repetitive transcranial magnetic stimulation treatment (rTMS) is an effective treatment for depression but the optimal methods of administration have yet to be determined. In particular, it is unclear whether there is a relationship between elements of the dose of stimulation (i.e., number of pulses) and clinical response. To address one aspect of dose, we conducted a trial comparing standard and high dose versions of high frequency left sided and low frequency right sided rTMS protocols (left standard = 50 trains, left high = 125 trains, right standard = 20 min, right high = 60 min, all per day in a single session). Method: 300 patients with treatment resistant depression were enrolled in a four arm randomized controlled trial across a four week time period. The primary outcome assessment was a comparison of response and remission rates on data from the 17-item Hamilton Rating Scale for Depression Rating Scale (HRSD-17). Results: The rate of response exceeded 45% in all groups. There was no significant difference between groups on initial analysis of the primary or secondary outcome measures (response rates: standard left = 52.5%, high left = 47.3%, standard right = 49.1%, high right = 48.4%). There was a greater remission rate with high compared to moderate dose left sided treatment when controlling for illness duration. We also found significant improvements in quality of life across all treatment groups. Illness duration was weakly associated with response. Conclusions: There was no consistent association between the antidepressant effect of rTMS and the number of TMS pulses provided across the ranges investigated in this study. Increasing TMS pulse number in individual sessions seems unlikely to be a method to substantially improve clinical outcomes, and future research should explore alternative means of improving clinical response. The study was registered on the Australian and New Zealand Clinical Trials Register (ACTRN12612000321842) https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=362063&isReview=true.