NCT05907369

Disgust Reduction Through Evaluative Conditioning (DREC) and tDCS in Contamination-Based OCD

Disgust Reduction Through Evaluative Conditioning and tDCS in Patients With Contamination-Based OCD

• Status: Unknown
• Phase: N/A
• Study type: Interventional
• Enrollment: 55 (estimated)
• Sponsor: Ferdowsi University of Mashhad · Academic / Other
• Sex: All
• Age: 18 Years – 55 Years
• Healthy volunteers: Not accepted

Summary

Obsessive-compulsive disorder (OCD) is a debilitating health condition that is known by intrusive and unwanted thoughts and repetitive behavioral or mental acts. 2-3% of the population suffers from OCD in their lifetime. The most common OCD subtype is contamination. The Serotonin-selective reuptake inhibitors (SSRIs) and cognitive-behavioral therapy (CBT) based on exposure and response prevention (ERP) technique are the first-line treatments for OCD. The challenge is that nearly half do not respond to the first-line treatments or have residual symptoms after completion of treatments. However, the prevalence of the disorder, diversity of symptoms, inadequate response rate, and necessity of having long-lasting treatment effects make the treatments of OCD more challenging. It seems that abnormal, more intense disgust experience has a prominent role in developing and maintaining OCD symptoms, particularly the contamination subtype. Evaluative conditioning (EC), defined as transferring the value of the US to the CS through pairing them, is the most common way of establishing disgust responses. The present study aims to develop an emotion-based intervention technique using EC targeting disgust emotion in contamination-based OCD (C-OCD). The hypothesis is that EC training may modify disgust experiences. Disgust may be the culprit, at least in part, of cognitive deficiencies in OCD. The other hypothesis is whether disgust reduction-focused EC may improve cognitive function, such as attention bias and inhibitory control. The orbitofrontal cortex (OFC) is one of the brain areas engaged in disgust processing and is mostly hyperactive in OCD patients. Cathodal transcranial direct current stimulation (tDCS) over OFC is one of the helpful neuromodulation methods in treating OCD. We aim to see if this method may help to regulate disgust experiences in combination with EC. The participants may be referred by psychiatrists or psychotherapists or be self-referred due to online advertisements or paper flyers. They will be randomly assigned to one of for arms of the study for sham or active EC training along with sham or active tDCS, to which they are blind. The novelty of the present study is the application of EC training in the clinical OCD population in combination with a neuromodulation method.

Detailed description

Disgust as a primary emotion has evolved to protect our lives by driving dirt and disease avoidance behaviors and motivating for cleaning and hygienic behaviors. In recent years, many studies have focused on the role of disgust in psychiatric disorders such as anxiety disorders, eating disorders, body dysmorphic disorders, and phobias. Nowadays, we have robust evidence of the correlation between disgust and the etiology and treatment of OCD symptoms, particularly the contamination subtype. The principal explanation for the insufficient treatment effect of ERP is that disgust is resistant to extinction. Since evaluative conditioning is one of the main sources of disgust feeling, the same process may effectively reduce disgust. The present trial will try to pair contamination-related pictures that are disgust-eliciting with positive, pleasant pictures in order to modify their disgust valence. We also will administer this EC training plus to OFC cathodal tDCS to see if the EC effect becomes more significant than EC alone.

Conditions

• Obsessive-Compulsive Disorder

Interventions

Type	Name	Description
OTHER	Active EC training	The active EC includes pairing contamination-related pictures (CSs) with pleasant pictures (USs). The EC training takes about 15 minutes and is administered for ten sessions (5 days a week) in 4 difficulty levels.
OTHER	Sham EC training	The active EC includes pairing contamination-related pictures (CSs) with neutral pictures (USs). The EC training takes about 15 minutes and is administered for ten sessions (5 days a week) in 4 difficulty levels, the same as active EC training.
OTHER	Active tDCS	For the active tDCS, the cathode is placed over the left OFC and the anode over the right cerebellum. The brain stimulation is delivered with a 2mA current intensity for 20 minutes in 10 sessions (5 days a week).
OTHER	Sham tDCS	For the sham tDCS, the cathode is placed over the left OFC and the anode over the right cerebellum, the same as active tDCS. The device is on for 20 minutes, but the current intensity is under the threshold of affecting cortical activity modulation. The participants receive the sham tDCS in 10 sessions (5 days a week).

Timeline

• Start date: 2023-01-20
• Primary completion: 2023-12-30
• Completion: 2024-03-29
• First posted: 2023-06-18
• Last updated: 2024-02-28

Locations

1 site across 1 country: Iran