Optimized multichannel tDCS protocol for clinical use in patients with major depressive disorder

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). Sixty patients with unipolar depression received 30 sessions of conventional, optimized multichannel, or sham tDCS in parallel groups. In the multichannel optimized tDCS, electrical current was delivered via 7 small electrodes while in the conventional and sham tDCS large anodal and cathodal electrodes were used. Intervention efficacy and treatment response were evaluated before treatment and after the 10th, 20th, 30th sessions, and 1- and 3-months post-intervention. Cognitive functions and brain connectivity were also assessed. 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.