Fronto-extracephalic transcranial direct current stimulation as a treatment for major depression: An open-label pilot study

Background: Several recent trials have reported transcranial direct current stimulation (tDCS) to be effective in treating depression, though the relative benefits of different electrode montages remain unexplored. Whereas all recent studies have used a bifrontal (BF) electrode montage, studies published in the 1960s and 1970s placed one electrode in an extracephalic position, with some positive reports of efficacy. This study investigated the efficacy and safety of tDCS given with a fronto-extracephalic (F-EX) montage. Methods: 2 mA tDCS was administered for 20 min every weekday over four weeks in 11 participants with a Major Depressive Episode who had previously shown inadequate response to, or relapsed following, a course of BF tDCS. For F-EX tDCS the anode was placed on the left dorsolateral prefrontal cortex and the cathode on the right upper arm. Depression severity and neuropsychological function were assessed before and after the treatment course. Antidepressant response was compared across an equivalent treatment period for both montages. Results: F-EX tDCS was shown to be safe and well tolerated. Depression ratings improved after acute treatment on the Montgomery Asberg Depression Rating Scale (p<0.001). Participants showed greater initial treatment response with F-EX tDCS than with BF tDCS (p<0.001). Limitations: This was an open label pilot study. The two comparison treatments were applied consecutively. Conclusion: F-EX tDCS appears to be safe and to have antidepressant effects, and may lead to more rapid improvement than tDCS given with a BF montage.