Repetitive transcranial magnetic stimulation: perspectives for application in the treatment of bipolar and unipolar disorders

Objectives: Transcranial magnetic stimulation (TMS) affects the brain by non-invasively stimulating the cerebral cortex and inducing electrical currents in neurons. The powerful magnetic field acts as a vector that passes across the scalp and the skull, and then converts into an electrical energy within the brain. Originally used in neurophysiology, TMS has since been applied in a variety of neuropsychiatric conditions, including mood disorders. Imaging studies in mood-disordered patients have pointed to dysfunctional limbic and prefrontal cortex activity. TMS researchers have thus postulated that dorsolateral prefrontal cortex (DLPFC) stimulation might change brain activity both locally and in paralimbic areas through transynaptic connections, and alter mood. Methods: We will describe the technology of TMS, its applications to date, and explore its mechanisms of action. Results: Several clinical trials have demonstrated TMS effects on mood in health and disease. There is a growing consensus that TMS has antidepressant effects, although little is known about the role played by a variety of stimulation parameters such as the intensity or frequency of stimulation. One study has found an antimanic effect of right prefrontal TMS. Conclusion: TMS is relatively safe; however, much more research is needed before TMS can be integrated into routine clinical practice.