Clinical and Electrophysiological Outcomes of tDCS in Patients With Treatment Resistant OCD

The aim of this study is to analyze the effectiveness of three different montages of transcranial direct current stimulation (tDCS) in treating treatment-resistant OCD.

Obsessive-compulsive disorder (OCD) typically starts between childhood and early adulthood and is characterized by the presence of obsessions and/or compulsions and a typically chronic clinical course. Around one-third of OCD patients fail to benefit significantly from first-line treatment, e.g., serotonin reuptake inhibitors (SRIs) or cognitive behavioral therapy (CBT). Combining, augmenting, and switching strategies as second-line treatments also fail to bring much benefit to these patients. When the first-line and second-line treatments fail, alternative treatments (e.g., non-invasive brain stimulation techniques) should be considered. A proposed pathophysiology of OCD is the dysfunction of cortico-striato-thalamo-cortical circuitry including the medial prefrontal cortex \[i.e., supplementary motor area (SMA) and anterior cingulate cortex (ACC)\], the dorso-lateral prefrontal cortex (DLPFC), the orbitofrontal cortex (OFC), and the basal ganglia. Among novel therapeutic options of non-invasive brain stimulation, transcranial direct current stimulation (tDCS) has shown positive results (e.g., cathodal tDCS over the pre-SMA, tDCS with the cathode over the left OFC and the anode over the right cerebellum, and tDCS with anode over Pre-SMA and cathode over right supra-orbital area) in treatment-resistant OCD. However, there is unclear evidence regarding the best tDCS montage for treatment-resistant OCD. This study investigates the effects of three different tDCS montages in reducing the symptoms of patients with treatment-resistant OCD. Eligible participants with treatment-resistant OCD will be allocated randomly into three groups of different tDCS montages \[1. The right cerebellum (anode) and the left OFC (cathode) tDCS; 2. The bilateral pre-SMA (cathode) and right deltoid (reference) tDCS; 3. The left OFC (cathode 1), bilateral pre-SMA (cathode 2), and right deltoid (reference) tDCS\]. Patients will receive twice-daily sessions separated by at least 1 h for 10 consecutive weekdays. One session of tDCS consists in delivering a direct current of 2 mA during 20 min. The primary outcome is the difference in the change of the score of the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) between three different montages of tDCS. Electrical activity of the brain as measured by EEG, autonomic function as measured by heart rate variability, and cognitive functioning as secondary outcomes will be measured before and after three different montages of tDCS.

Eligibility Criteria:
Inclusion Criteria:

* Eligible participants aged 20-65 with the primary clinical diagnosis of DSM-5-defined obsessive-compulsive disorder.
* Being treatment-resistant, as revealed by a Yale-Brown Obsessive and Compulsive Scale score (Y-BOCS) \>16 despite at least two selective serotonin reuptake inhibitor (SSRI) trials of adequate dose and duration (or refusal to take medication for personal choice) and having been offered prior cognitive behavior therapy (CBT) by a trained practitioner.
* The dosages of undergoing psychopharmacological medications having remained unchanged for 1 month before the beginning of the trial and remaining unchanged throughout the entire duration of the study.
* Agreement to participate in the study and provide the written informed consent.

Exclusion Criteria:

* Having contraindications for transcranial electrical stimulation or transcranial magnetic stimulation, e.g., pacemakers, metallic or magnetic pieces in the head/brain, ear implants and other implantable brain medical devices.
* Pregnancy or breastfeeding at enrollment.
* Having active substance use disorder (in exception to caffeine and/or tobacco).
* Having a history of seizures.
* Having a history of intracranial neoplasms or surgery, or a history of severe head injuries or cerebrovascular diseases.
* Skin lesions on scalp at the area of electrode application.
* Having unstable medical conditions at enrollment.