Is more better? Comparing 600, 1200 and 1800 pulses/session (p/s) of intermittent theta-burst stimulation (iTBS) for the treatment of depression.

Introduction: Repetitive Transcranial magnetic stimulation (rTMS) is a non-invasive therapy for treatment-resistant disorders. Intermittent theta-burst stimulation (iTBS) has emerged as a favorite treatment protocol for the treatment of therapy resistant depression, with the tendency to administer an increasing number of pulses/session (p/s).

Methods: We retrospectively analyzed the records of 215 in- and out-patients, suffering from unipolar or bipolar depressive disorder in a German tertiary care hospital between January 2021 and September 2024. All patients received left prefrontal iTBS with either 600 (n = 68), 1200 (n = 67) or 1800 (n = 80) p/s over the course of 15-20 days. Depressive symptoms were assessed with the 21-item Hamilton Depression Rating Scale (HAMD-21) and the Major Depression Inventory (MDI) before and at the end of the respective treatment. Side effects were quantified by the number of patients reporting a side effect in at least one of the rTMS sessions.

Results: In all groups, the HAMD-21 and MDI scores improved significantly. There was no significant difference between the three groups (HAMD-21: p = .198, MDI: p = .281). Further, this result equally applies to men and women (all p's > .145). No serious side effects occurred. Patients who were treated with 600 p/s reported most side effects.

Conclusion: Our retrospective analysis suggests that an increase of p/s from 600 to 1200 or 1800 does not result in more pronounced antidepressant effects.