Within-Session Mood Changes From TMS in Depressed Patients

Abstract

Transcranial magnetic stimulation has become an increasingly well studied tool in neuropsychiatry. It has been applied in neurophysiology and as a treatment modality in various neurological and psychiatric disorders. Regarding the treatment of major depressive disorder, several meta-analyses of a number of randomized sham-controlled trials using repetitive transcranial magnetic stimulation (TMS), 1–6 have produced a significant body of evidence supporting its efficacy. Target areas of repetitive TMS in the treatment of mood disorders are the left and the right prefrontal cortex. The selection of these areas is based on evidence from neuroimaging and neuropsychological studies that suggest that prefrontal cortical areas show significant abnormalities in mood disorders. 7–10 During treatment with TMS, magnetic pulses are applied to the scalp. These pulses induce an electrical current in the underlying cortical tissue which results in depolarization of cortical neurons. Indirectly TMS also has effects on related cortical and subcortical areas as evidenced by studies of the motor cortex. 11,12 TMS studies regarding mood disorders have focused largely on depressed patients during a course of TMS, which usually consists of multiple treatment sessions conducted over several weeks. In contrast, studies regarding immediate effects of TMS on mood and on neural networks have mostly assessed healthy subjects. Reasons for studying healthy subjects rather than depressed patients include concerns about symptom heterogeneity in depression and the impact of psychotropic medications. 13,14