Transcranial direct current stimulation improve symptoms and modulates cortical inhibition in obsessive-compulsive disorder: A TMS-EEG study

Background: Obsessive-compulsive disorder (OCD) is a disabling condition for which approximately 40% of patients do not respond to first-line treatment. Transcranial direct current stimulation (tDCS) is a safe and accessible technique that modulates cortical excitability and inhibition, but evidence of its efficacy for OCD is insufficient. Objective: To investigate the efficacy of tDCS for OCD and alterations of cortical excitability and inhibition after treatment measured by concurrent transcranial magnetic stimulation-electroencephalography (TMS-EEG). Methods: Twenty-four OCD patients underwent 10 20-min sessions of 1.5 mA high-definition tDCS with a cathode placed over the right orbitofrontal cortex (OFC) and anode electrodes set around the cathodal electrode. TMSEEG was performed before and after tDCS treatment. OCD symptom severitys was assessed using Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), and the Beck Depression Inventory-II (BDI-II), and Beck Anxiety Inventory (BAI) were used to assess the severity of depression and anxiety symptoms. Twenty-seven healthy controls were recruited with TMS-EEG recorded. Results: Following tDCS, the Y-BOCS, BDI-II, and BAI scores decreased significantly (all p = 0.000). TMS-evoked N100 amplitude, thought to be related to GABAB receptor function, was significantly reduced after tDCS (Z =-2.143, p = 0.032) which was higher in OCD patients than in healthy controls at baseline (Z =-2.151, p = 0.031). Limitations: Pharmacotherapy during tDCS treatment may influence the effect of tDCS and EEG. Conclusions: Cathodal high-definition tDCS applied over the OFC could improve OCD, depression, and anxiety symptoms along with alleviation of GABAB receptor function.