Transcranial direct current stimulation (tDCS)
Stimulation was administered using a CE-certified microprocessor-controlled device (Sooma tDCS, Sooma Medical, Helsinki, Finland) that emitted a direct current (DC) with a maximum output of 2 mA. A pair of conductive rubber square electrodes (anode and cathode) with dimensions of 5 × 7 cm (35 cmThe four stimulation devices (A, B, C, and D) were preprogrammed to provide either real stimulation (devices A and C, with a DC of 2.00 mA) or sham stimulation (devices B and D, with a DC of 0.30 mA). In the sham stimulation mode, the devices initially provided DC of 2.00 mA, immediately ramping down to a DC of 0.30 mA and maintaining this current for 30 min (treatment duration), thereby producing sensations similar to real stimulation.Stimulation was carried out according to the manufacturer’s protocol, which entailed three weeks of treatment with daily 30-min stimulation sessions for 15 sessions. This protocol was used irrespective of the device mode (real or sham stimulation). In our trial, participants received tDCS or sham stimulation until the end of week 3, from Monday to Friday, between 2:00 and 4:00 PM, with stimulation pauses at weekends.