Cathodal tDCS in obsessive-compulsive disorder: cognitive and neurophysiological outcomes in a double-blind sham-controlled trial

Abstract

Objective This preliminary study examined the efficacy of cathodal transcranial direct current stimulation (tDCS) targeting the medial prefrontal cortex (mPFC) in reducing symptom severity, enhancing cognitive flexibility, and modulating brain-derived neurotrophic factor (BDNF) levels in individuals with obsessive-compulsive disorder (OCD). Methods A double-blind, randomized, sham-controlled trial was conducted with 20 patients meeting DSM-V criteria for OCD, of whom 15 completed the intervention and were included in the final analysis. Participants received cathodal mPFC-tDCS (2 mA, 20 min, 10 sessions) or sham stimulation. Symptom severity (Y-BOCS), cognitive flexibility (task-switching), salivary BDNF, and frontal alpha activity (qEEG at Fz) were measured at baseline, post-treatment, and follow-up. Results The tDCS group exhibited greater reductions in Y-BOCS scores over time (F(2, 26) = 12.562, p < 0.001, partial η2 = 0.425). Task-switching performance improved in the experimental group compared with controls (F(2, 26) = 20.351, p < 0.001, partial η2 = 0.531). Salivary BDNF levels increased significantly in the tDCS group at follow-up (F(2, 16) = 6.086, p = 0.01, partial η2 = 0.432). Trends toward normalization of frontal alpha activity were observed, but did not reach statistical significance. Conclusions Cathodal mPFC-tDCS was associated with reduced OCD symptom severity, improved cognitive flexibility, and increased salivary BDNF. These preliminary findings warrant replication in larger controlled samples. Significance This study extends previous tDCS research in OCD by integrating clinical outcomes with cognitive performance and a peripheral marker of neuroplasticity. It provides preliminary support for mPFC-targeted tDCS as a potential intervention for OCD.