A review of transcranial direct current stimulation (tDCS) for the individualized treatment of depressive symptoms - PubMed (original) (raw)

A review of transcranial direct current stimulation (tDCS) for the individualized treatment of depressive symptoms

Mayank V Jog et al. Pers Med Psychiatry. 2019 Nov-Dec.

Abstract

Transcranial direct current stimulation (tDCS) is a low intensity neuromodulation technique shown to elicit therapeutic effects in a number of neuropsychological conditions. Independent randomized sham-controlled trials and meta- and mega-analyses demonstrate that tDCS targeted to the left dorsolateral prefrontal cortex can produce a clinically meaningful response in patients with major depressive disorder (MDD), but effects are small to moderate in size. However, the heterogeneous presentation, and the neurobiology underlying particular features of depression suggest clinical outcomes might benefit from empirically informed patient selection. In this review, we summarize the status of tDCS research in MDD with focus on the clinical, biological, and intrinsic and extrinsic factors shown to enhance or predict antidepressant response. We also discuss research strategies for optimizing tDCS to improve patient-specific clinical outcomes. TDCS appears suited for both bipolar and unipolar depression, but is less effective in treatment resistant depression. TDCS may also better target core aspects of depressed mood over vegetative symptoms, while pretreatment patient characteristics might inform subsequent response. Peripheral blood markers of gene and immune system function have not yet proven useful as predictors or correlates of tDCS response. Though further research is needed, several lines of evidence suggest that tDCS administered in combination with pharmacological and cognitive behavioral interventions can improve outcomes. Tailoring stimulation to the functional and structural anatomy and/or connectivity of individual patients can maximize physiological response in targeted networks, which in turn could translate to therapeutic benefits.

Keywords: Transcranial electrical stimulation (TES); antidepressant treatment; direct current; major depression; neuromodulation.

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Conflict of interest statement

Declarations of interest: none

Figures

Figure 1.

Figure 1.. Simultaneous mapping of tDCS electric currents and functional changes in a sample subject.

Concurrent tDCS-MRI data can be acquired as shown, with the phase and magnitude of the MR signal encoding the current induced magnetic field (along Bz) and BOLD-contrast respectively. While the former is linearly proportional to tDCS electric currents along an orthogonal direction (Ampere’s Law), the latter is an established marker for tracking brain activity. An ICA analysis on the BOLD-data identified brain networks including the default mode network (green) and the executive networks (brown). The analysis also identified two regions underneath the anode and cathode electrodes (labelled "anodal" and "cathodal"), which were found to correlate significantly with the applied tDCS current.

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