Adjunctive High-Definition Transcranial Direct Current Stimulation in Treatment of Resistant Auditory Verbal...

Resistant auditory verbal hallucination (AVH) remains a disabling symptom in schizophrenia. Transcranial direct current stimulation (tDCS) and its more targeted variant, high-definition tDCS (HD-tDCS), have shown promising results in reducing AVH. We aimed to determine the effects of adjunctive HD-tDCS on various dimensions of AVH in patients with schizophrenia.

This randomized controlled trial included 40 patients with schizophrenia with resistant AVH (20 patients each assigned to the active and sham group). A stimulation electrode was placed over the left temporoparietal junction at CP5 according to the 10-10 EEG montage, while return electrodes were positioned at C3, T7, P3, and P7. The active group received 2-mA current for 20 minutes, with a ramp-up and ramp-down of 3 seconds, whereas the sham group received 1-mA current for 30 seconds, with a 3-second ramp-up and ramp-down. AVH severity was assessed using the Psychotic Symptom Rating Scale-Auditory Hallucination at baseline, at the end of HD-tDCS sessions, and 4 weeks after completion.

Within-group comparisons revealed significant improvements in both groups. However, in time*group comparison, the group receiving active HD-tDCS showed a statistically significant improvement only in the frequency dimension of AVH over time ( p  = 0.011). No other dimensions of AVH improved significantly in the time*group comparison. The effects of HD-tDCS were sustained up to 4 weeks.

Active HD-tDCS over the left temporoparietal junction significantly reduced the frequency of AVH in patients with schizophrenia compared to sham stimulation. However, no significant improvements were observed in other domains of hallucination.