Transcranial magnetic stimulation in major depressive disorder: Response modulation and state dependency

Background: Transcranial Magnetic Stimulation (TMS) has emerged as a valid therapeutic option in the treatment of depression, especially in cases of inadequate response to antidepressant agents. Despite the recognized efficacy of this technique, its mechanisms of action are still debated and optimal protocols have not yet been established. Methods: The present review focuses on TMS protocols that either engage the targeted brain circuits or synchronize the stimulation frequency to individual neuronal oscillations to increase the antidepressant efficacy. Results: TMS efficacy was found to be enhanced by preliminary or concomitant modulation of the functional state of the targeted brain networks. Conversely, there is not enough evidence of higher efficacy of TMS protocols with individual selection of the stimulation frequency compared to standard ones. Limitations: Most studies included small patient samples. Conclusions: Our results suggest that a good option to enhance rTMS efficacy might be to follow synaptic potentiation and depression rules.