Optimized multichannel tDCS protocol for clinical use in patients with major depressive disorder: A randomized, controlled trial

Application of transcranial direct current stimulation (tDCS) has been increased in neuropsychiatric disorders, especially depression, in the last decade. Despite promising results, the clinical efficacy of tDCS is still under debate and researchers and clinicians try to maximize efficacy by developing optimized/individualized protocols. In this randomized sham-controlled, parallel-group clinical trial, we optimized a stimulation protocol for increasing and decreasing activity in the left and right dorsolateral prefrontal cortex (DLPFC). 60 patients with major depression were recruited and randomly assigned to active conventional tDCS (N=20), active multichannel tDCS (N=20), or sham tDCS (N=20) groups. Patients in each group received 30 sessions of active or sham tDCS for 5 days per week. In the multichannel optimized tDCS, electrical current was delivered via 7 small electrodes (11 mm in diameter) with 2 mA intensity with a maximum total injected current set to 4.0 mA. In the conventional tDCS (2 mA intensity, electrode size of 35 cm2) and sham Tdcs, anodal and cathodal electrodes were placed over the left and right DLPFC respectively. Symptoms severity (measured by the Hamilton Depression Rating Scale- HDRS, Beck Depression Inventory- BDI-II, and Montgomery–Åsberg Depression Rating Scale- MADRS) were assessed before the intervention, after sessions 10th, 20th, and right after the intervention (session 30th), and 1 and 3 months following the intervention. Compared to the sham group, both active tDCS groups significantly reduced depressive symptoms up to 3 months following the intervention, and the therapeutic effects were observed from session 10th only in the multichannel tDCS groups. Furthermore, the effect size from the optimized multichannel protocol was significantly larger than the conventional tDCS. These data suggest that optimized multichannel tDCS might maximize therapeutic efficacy in major depression.