Accelerated high-capacity 6 mA transcranial direct current stimulation for major depression

Home-based 2 mA transcranial direct current stimulation (tDCS) is FDA-approved for depression, but amplitude has been limited largely by skin tolerance. This study evaluated the safety, tolerability, and feasibility of accelerated high-capacity tDCS (HC-tDCS) at 6 mA.

In this open-label pilot study, 20 patients with major depressive disorder received 20-minute bifrontal 6 mA sessions twice daily for five days using a high-capacity stimulator and hydrogel electrodes. A Safety Review Committee reviewed data from the first three participants before the remaining 17 were enrolled.

Retention and adherence were 100% (203 of 203 sessions); 17 of 20 received 6 mA throughout, with amplitude reduced for intolerance in one and limited by an electrode fault in two. There were no serious adverse events. The most common symptoms were fatigue (49% of sessions), burning (46%) and tingling (43%) at the electrode, and difficulty concentrating (40%). Electrode-site erythema occurred in all participants, with no severe reactions. At 1 week, 7 of 20 reported a residual skin change, none painful; at 1 month, spots of residual pigmentation were observed at the electrode site in 2 participants, both Black. In five days, mean PHQ-9 scores decreased from 15.8 to 7.2 (Hedges g=1.62); 50% of participants responded, 45% remitted, and improvement was maintained at 1 month. Anhedonia, mindfulness, and self-reported cognitive function also improved (g=0.76 to 1.23), with gains maintained at 1 month.

Accelerated 6 mA HC-tDCS was feasible, well tolerated, and warrants a sham-controlled trial.