Dosing transcranial magnetic stimulation in major depressive disorder: Relations between number of treatment sessions and effectiveness in a large patient registry

Abstract

BackgroundThe number of sessions in an acute TMS course for major depressive disorder (MDD) is greater than in the earlier randomized controlled trials. ObjectiveTo compare clinical outcomes in groups that received differing numbers of TMS sessions. MethodsFrom a registry sample (N = 13,732), data were extracted for 7215 patients treated for MDD with PHQ-9 assessments before and after their TMS course. Groups were defined by number of acute course treatment sessions: 1–19 (N = 658), 20–29 (N = 616), 30–35 (N = 1375), 36 (N = 3591), 37–41 (N = 626), or >41 (N = 349) and compared in clinical outcomes at endpoint and at fixed intervals (after 10, 20, 30, and 36 sessions). The impact of additional treatments beyond 36 sessions was also examined. ResultsGroups that received fewer than 30 sessions had inferior endpoint outcomes than all other groups. PHQ-9 symptom reduction was greatest in the group that ended treatment at 36 sessions. The extended treatment groups (>36 sessions) differed from all other groups by manifesting less antidepressant response early in the course and had a slower but steady rate of improvement over time. Extending treatment beyond 36 sessions was associated with further improvement without evidence of a plateau. ConclusionsIn real-world practice, there are strong relations between the number of TMS sessions in a course and the magnitude of symptom reduction. Courses with less than 30 sessions are associated with diminished benefit. Patients with longer than standard courses typically show less initial improvement and a more gradual trajectory, but meaningful benefit accrues with treatment beyond 36 sessions.