Improved decision-making in patients with mood disorders following Transcranial Direct Current Stimulation (tDCS) applied to the left orbitofrontal cortex: A proof-of-concept study

Deficits in decision-making is found in several mental disorders, including anorexia nervosa, addiction, mood disorders, and suicidal behavior. Improving decision-making is a relevant therapeutic objective to reduce vulnerability and risky behaviors. Transcranial Direct Current Stimulation (tDCS) is a simple and non-invasive technique that allows for the stimulation of a cortical area of interest. Previous studies have shown that tDCS of the orbitofrontal cortex (OFC) in healthy volunteers improves decision-making in the short-term. We aimed to demonstrate this short-term effect in patients with a mood disorder. This was a prospective, single-center, interventional, randomized controlled trial (ClinicalTrial.gov NCT06110559) with two parallel arms (active vs sham stimulation) in a single-blind design. tDCS was applied during 30 min over the left OFC (anode Fp1/cathode Fp2). The primary outcome was a change in the net score on the Iowa Gambling Task (IGT) measured immediately before and after stimulation. Sixty-two patients were randomized to receive active (N = 30) or sham (N = 32) stimulation. We observed a significant improvement in IGT net score in the active vs sham arm (time*arm interaction χ² = 4.10; p = .043). No significant change at other cognitive tasks (d2, Go/No-Go, Emotional Stroop) or self-rating perceived emotion questionnaires (PANAS, STAI-Y-A) was found. Patients did not correctly guess the treatment arm. These preliminary findings support the use of tDCS over the OFC to improve decision-making in patients with mood disorders. Future studies should assess the best strategies for sustained improvement, and the naturalistic consequences in terms of real-life decision-making and functioning.