Transcranial direct current stimulation (tDCS) as treatment for major depression–analysis of the first technical data from a blind selection of active tDCS sessions

Abstract

Introduction Transcranial direct current stimulation (tDCS) has been proposed as novel treatment for major depressive disorder (MDD), based on clinical pilot studies as well as randomized controlled monocentric trials. Methods The DepressionDC study investigates efficacy and tolerability of prefrontal tDCS used as an additive therapy to an antidepressant medication (SSRI) as treatment for major depression in a double-blinded, randomized, placebo-controlled multicenter trial [1] . There is a consensus on parameters like electrical current (1–2 mA) and the critical impedance values are known from safety-studies, but the in vivo stability of these technical parameters over the stimulation period has not been investigated yet. For the DepressionDC study a novel system for recording and monitoring of technical data has been established in order to continuously control tDCS quality and allow posthoc analysis of technical data in conjunction with clinical outcome criteria. Here, we present a blind analysis of the technical data of 280 active tDCS sessions from multiple centers in order to monitor tDCS quality at this stage of the study. The descriptive analysis showed high homogeneity and stability of the technical parameters over the time of the tDCS session in 120 active stimulations from a single center, as well as in 160 active stimulations across different study sites. To determine tDCS-affected brain areas we leveraged the freely available Simnibs 2.0.1. software to develop subject-specific head model based on MRI data and calculate electric fields (and current density) induced by tDCS. Calculating the electric field, the peak electric field strength as well as activation graduation by percentiles in every single subject, revealed stable and homogenous activation patterns in all participants. Online recording of technical parameters across centers and individual e-field modelling for defining tDCS dosage at target sites are promising deliverables from the DepressionDC trial for further clinical applications.