Psychoneuroimmunological mechanisms contribute to the onset and persistence of stress-induced gastric ulcers by delaying wound healing and exacerbating gastric inflammation. Anodal transcranial direct current stimulation (tDCS) targeting the left dorsolateral prefrontal cortex has demonstrated promising effects in modulating central pain processing and emotional regulation across various chronic pain conditions. This quasi-experimental study with a repeated-measures design aimed to evaluate the efficacy of 30 sessions of anodal transcranial direct current stimulation (tDCS) targeting the left dorsolateral prefrontal cortex (L-DLPFC; electrode position F3) versus placebo in alleviating pain and psychological distress among patients with chronic gastric pain. A total of 50 patients (aged 14-80 years) with chronic gastric pain and no severe structural pathology were recruited from Tehran and Bonab, Iran, and randomly assigned to active tDCS (n = 25) or sham stimulation (n = 25) after matching. The intervention consisted of 30 sessions of anodal tDCS (2 mA, 20 min per session) over 6 weeks. Outcome measures included the visual analog scale (VAS) for pain intensity and the Kessler Psychological Distress Scale (K10). Data were analyzed using split-plot analysis of variance (SPANOVA). Results showed that anodal tDCS over the L-DLPFC produced significant improvements in psychological status and a substantial reduction in gastric pain compared to the sham group. In the experimental group, mean pain scores decreased from 7.41 ± 0.96 at baseline to 3.40 ± 1.82 postintervention and 2.23 ± 1.86 at 2-month follow-up. K10 scores declined from 32.4 ± 8.25 to 18.51 ± 7.02 and 17.00 ± 8.49, respectively. These findings indicate that noninvasive neuromodulation via anodal tDCS targeting the L-DLPFC may offer a promising adjunctive therapeutic approach for chronic gastric pain by modulating central pain processing and the gut-brain axis, with potential implications for advancing the understanding and clinical management of psychosomatic gastrointestinal disorders.
