Repetitive transcranial magnetic stimulation (rTMS) of the dorsolateral-prefrontal cortex (DLPFC) with conventional figure-of-8 (=butterfly) coils has been used as an antidepressant therapeutic tool for almost twenty years. Very recently, an innovative rTMS coil, the so-called double cone coil (DC), was introduced allowing the modulation of the anterior cingulate cortex (AC). We investigated safety and therapeutic effectiveness of this stimulation in a naturalistic clinical setting.

Forty-five patients suffering a moderate to severe depressive episode were randomized to receive 15 sessions of either conventional rTMS of the left DLPFC (“butterfly-rTMS”; 10 Hz; 2000 stimuli/day, RMT 110%), mediofrontal double cone coil stimulation of the anterior cingulate cortex (“ACDC-rTMS” with equal parameters), or sham-stimulation. The primary outcome was the change in the 21-items Hamilton Rating Scale for Depression (HAMD) from baseline to the end of treatment. Secondary outcome measures were changes over the course of the trial regarding the HAMD, the Beck Depression Inventory (BDI), the Clinical Global Impression (CGI) and the Global Assessment of Functioning (GAF) scales.

There was a significant group × time interaction effect regarding the primary outcome (F = 3.269; df = 2,37; P = 0.049). Post-hoc t-testing revealed a significant effect for the comparison ACDC vs. butterfly at week 3/end of treatment (T = 2.646; df = 26; P = 0.014). No severe adverse events occurred during the study. ACDC-stimulation was well tolerated by the majority of patients similar like butterfly-rTMS and sham-stimulation.

This pilot study demonstrated the feasibility of ACDC-rTMS-stimulation as an add-on-treatment for depression. Its clinical effects warrant further investigation in the future.