Obsessive-Compulsive DisorderNCT05907369
Disgust Reduction Through Evaluative Conditioning (DREC) and tDCS in Contamination-Based OCD
A study testing Active EC training and Active tDCS in people with Obsessive-Compulsive Disorder, run by Ferdowsi University of Mashhad at 1 site in Iran.
Trial 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. Read more about this study
- Who is it for?
- Ages 18 to 55 years
- Conditions the study is for
- Obsessive-Compulsive Disorder
- What is being tested?
- Active EC training and Active tDCS
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 55 participants
- Where
- 1 siteIran
- Study dates
- 20 Jan 2023to 29 Mar 2024
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 55 years
- All sexes
- No healthy volunteers
- Adult
Who may be able to join
- The Diagnostic criteria of OCD in the Diagnostic and Statistical Manual of Mental Disorders 5th edition (DSM-5-TR) with the symptoms of contamination subtype
- Able to read, write and do computerized tasks
- Stable medication for at least the last three months
- Filling out the written consent
Who cannot join
- Severe physical illness
- Severe other mental disorders
- Alcohol and drug dependence
- A history of epilepsy or seizure
- Have metal or electronic implants in the head or use a cardiac pacemaker
- History of head trauma or neurological disorders
- Women who are pregnant or may be pregnant
- Unable to complete questionnaires, computerized tasks, or informed consent
Trial locations and contacts
1 site in 1 country.
Iran1 site, 1 recruiting
- Recruiting
Ferdowsi University of Mashhad
Mashhad, Razavi Khorasan Province, 91779 48974
Ali Moghimi, PhD, 0098 09153176390, moghimi@um.ac.ir
Faezeh Raeisalmohaddesin, MsC, 0098 09151232724, fh.raeesi@gmail.com
About this study
Official title: Disgust Reduction Through Evaluative Conditioning and tDCS in Patients With Contamination-Based OCD
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.
Read the 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
- Being tested
- Active EC training, Sham EC training, Active tDCS, Sham tDCS
- Keywords
- Obsessive-Compulsive Disorder, Contamination symptoms, Disgust, Evaluative Conditioning, Transcranial Direct Current Stimulation, Orbitofrontal Cortex
- Medical subject headings
- Obsessive-Compulsive Disorder
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Active EC trainingOther
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.
Sham EC trainingOther
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.
Active tDCSOther
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).
Sham tDCSOther
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).
| Study group | Role | What they receive |
|---|---|---|
| aEC/ stDCS | Experimental | Participants in this group receive active EC training but sham tDCS. Receives: Other: Active EC training; Other: Sham tDCS |
| sEC/atDCS | Active comparator | Participants in this group receive active tDCS training but sham EC training. Receives: Other: Sham EC training; Other: Active tDCS |
| aEC/atDCS | Experimental | Participants in this group receive both active EC training and active tDCS. Receives: Other: Active EC training; Other: Active tDCS |
| sEC/stDCS | Sham comparator | Participants in this group receive the sham EC training and also sham tDCS. Receives: Other: Sham EC training; Other: Sham tDCS |
What is being measured
The primary outcome is the main question the study is designed to answer.
Disgust Feeling
Effect of evaluative conditioning, cathodal tDCS over OFC, and both on changing disgust feeling intensity measured by disgust rating scale. The scale rates from 0 (not disgusting) to 10 (very disgusting). Lower scores show less disgust feeling.
Measured: From pre- to post-assessment (2 weeks after baseline assessment) and from pre- to follow-up assessment (10 weeks after baseline assessment)
Clinical Symptoms Severity of Contamination-Based OCD
Change in Clinical symptoms of contamination-based OCD after evaluative conditioning, cathodal tDCS over OFC, and both, measured by Yale-Brown Obsessive-Compulsive scale. It is scored on a 5-point rating. The lower scores show less symptom severity.
Measured: From pre- to post-assessment (2 weeks after baseline assessment) and from pre- to follow-up assessment (10 weeks after baseline assessment)
Secondary outcomes (3)
The power spectrum of brain waves based on quantitative electroencephalogram
Effect of evaluative conditioning, cathodal tDCS over OFC, and both on power spectrum of recorded brain waves.
Measured: From pre- to post-assessment (2 weeks after baseline assessment) and from pre- to follow-up assessment (10 weeks after baseline assessment)
Attentional bias
Change in attentional bias toward contamination stimuli, measured by Dot-prob test, comparing evaluative conditioning, cathodal tDCS over OFC, and both.
Measured: From pre- to post-assessment (2 weeks after baseline assessment) and from pre- to follow-up assessment (10 weeks after baseline assessment)
Inhibitory control
Change in inhibitory control, measured by go/nogo and stop-signal tests, comparing evaluative conditioning, cathodal tDCS over OFC, and both.
Measured: From pre- to post-assessment (2 weeks after baseline assessment) and from pre- to follow-up assessment (10 weeks after baseline assessment)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted18 Jun 2023
- Study start20 Jan 2023
- Primary completion30 Dec 2023
- Study completion29 Mar 2024 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (2)Papers the sponsor has linked to this study.
- Other trials for Obsessive-Compulsive DisorderStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Factorial
- Model description
- The two interventions include evaluative conditioning (EC) training and cathodal tDCS over OFC. Each is present in two forms: active and sham. So, there are four interventional conditions, including sham EC-sham tDCS, active EC- sham tDCS, sham EC-active tDCS, and active EC-active tDCS.
- Masking
- Single blind
- Who is masked
- Participant
- Enrolment
- 55 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Ferdowsi University of Mashhad
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Ali Moghimi, Ferdowsi University of Mashhad
- Investigators
- Ali Moghimi, PhD, Study director, Ferdowsi University of Mashhad
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05907369
- Sponsor's protocol ID
- 3/56765
- Other IDs
- 100/18979
- Status last verified
- Sep 2023
- First submitted
- 15 May 2023
- Last updated
- 28 Feb 2024
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Raeis Al Mohaddesin F, Moghimi A, Kobravi H, Yaghoubian E, Salehi Fadardi J. Disgust-reduction evaluative conditioning (DREC) and tDCS in contamination-based OCD: a randomized controlled trial. BMC Psychiatry. 2026 Apr 6;26(1):414. doi: 10.1186/s12888-026-07934-0.
PubMed 41942946Al Mohaddesin FR, Moghimi A, Fadardi JS. Disgust-reduction evaluative conditioning (DREC) and brain stimulation in patients with contamination-based obsessive-compulsive disorder: a protocol for a randomized control trial. Trials. 2023 Nov 24;24(1):750. doi: 10.1186/s13063-023-07791-2.
PubMed 38001473
Study at a glance
From the registry record, last updated by the sponsor on 28 Feb 2024. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Disgust Reduction Through Evaluative Conditioning and tDCS in Patients With Contamination-Based OCD
- ClinicalTrials.gov ID
- NCT05907369
- Acronym / sponsor ID
- 3/56765
- Conditions
- Obsessive-Compulsive Disorder
- Keywords
- Obsessive-Compulsive Disorder, Contamination symptoms, Disgust, Evaluative Conditioning, Transcranial Direct Current Stimulation, Orbitofrontal Cortex
- Study type
- Interventional
- Recruitment status
- Unknown status
- Enrolment
- 55 participants (estimated)
- Lead sponsor
- Ferdowsi University of MashhadUniversity, hospital or other
- Study start
- 20 Jan 2023 (actual)
- Primary completion
- 30 Dec 2023 (actual)
- Study completion
- 29 Mar 2024 (estimated)
- First posted
- 18 Jun 2023 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Factorial
- Masking
- Single blind (participant)
- Number of arms
- 4
- Model description
- The two interventions include evaluative conditioning (EC) training and cathodal tDCS over OFC. Each is present in two forms: active and sham. So, there are four interventional conditions, including sham EC-sham tDCS, active EC- sham tDCS, sham EC-active tDCS, and active EC-active tDCS.
| Arm | Type | Receives |
|---|---|---|
| aEC/ stDCS | Experimental | Other: Active EC training, Other: Sham tDCSParticipants in this group receive active EC training but sham tDCS. |
| sEC/atDCS | Active comparator | Other: Sham EC training, Other: Active tDCSParticipants in this group receive active tDCS training but sham EC training. |
| aEC/atDCS | Experimental | Other: Active EC training, Other: Active tDCSParticipants in this group receive both active EC training and active tDCS. |
| sEC/stDCS | Sham comparator | Other: Sham EC training, Other: Sham tDCSParticipants in this group receive the sham EC training and also sham tDCS. |
Who may qualify
- Ages
- 18 to 55 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult
Key inclusion criteria (4 listed)
- The Diagnostic criteria of OCD in the Diagnostic and Statistical Manual of Mental Disorders 5th edition (DSM-5-TR) with the symptoms of contamination subtype
- Able to read, write and do computerized tasks
- Stable medication for at least the last three months
- Filling out the written consent
Key exclusion criteria (8 listed)
- Severe physical illness
- Severe other mental disorders
- Alcohol and drug dependence
- A history of epilepsy or seizure
- Have metal or electronic implants in the head or use a cardiac pacemaker
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Active EC trainingThe 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 | aEC/ stDCS, aEC/atDCS |
| Sham EC trainingThe 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 | sEC/atDCS, sEC/stDCS |
| Active tDCSFor 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 | aEC/atDCS, sEC/atDCS |
| Sham tDCSFor 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). | Other | aEC/ stDCS, sEC/stDCS |
Primary outcome
Disgust Feeling
Time frame: From pre- to post-assessment (2 weeks after baseline assessment) and from pre- to follow-up assessment (10 weeks after baseline assessment)
Effect of evaluative conditioning, cathodal tDCS over OFC, and both on changing disgust feeling intensity measured by disgust rating scale. The scale rates from 0 (not disgusting) to 10 (very disgusting). Lower scores show less disgust feeling.
Clinical Symptoms Severity of Contamination-Based OCD
Time frame: From pre- to post-assessment (2 weeks after baseline assessment) and from pre- to follow-up assessment (10 weeks after baseline assessment)
Change in Clinical symptoms of contamination-based OCD after evaluative conditioning, cathodal tDCS over OFC, and both, measured by Yale-Brown Obsessive-Compulsive scale. It is scored on a 5-point rating. The lower scores show less symptom severity.
3 secondary outcomes
The power spectrum of brain waves based on quantitative electroencephalogram
Time frame: From pre- to post-assessment (2 weeks after baseline assessment) and from pre- to follow-up assessment (10 weeks after baseline assessment)
Attentional bias
Time frame: From pre- to post-assessment (2 weeks after baseline assessment) and from pre- to follow-up assessment (10 weeks after baseline assessment)
Inhibitory control
Time frame: From pre- to post-assessment (2 weeks after baseline assessment) and from pre- to follow-up assessment (10 weeks after baseline assessment)
Results and safety
Results are not available in the source record.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 28 Feb 2024.
- Derived from this study: PubMed 41942946Raeis Al Mohaddesin F, Moghimi A, Kobravi H, Yaghoubian E, Salehi Fadardi J. Disgust-reduction evaluative conditioning (DREC) and tDCS in contamination-based OCD: a randomized controlled trial. BMC Psychiatry. 2026 Apr 6;26(1):414. doi: 10.1186/s12888-026-07934-0.
- Derived from this study: PubMed 38001473Al Mohaddesin FR, Moghimi A, Fadardi JS. Disgust-reduction evaluative conditioning (DREC) and brain stimulation in patients with contamination-based obsessive-compulsive disorder: a protocol for a randomized control trial. Trials. 2023 Nov 24;24(1):750. doi: 10.1186/s13063-023-07791-2.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Ali Moghimi, PhD study director
Ferdowsi University of Mashhad
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Active EC training and Active tDCS in people with Obsessive-Compulsive Disorder, run by Ferdowsi University of Mashhad at 1 site in Iran.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: status not confirmed, as of the sponsor's last update on 28 Feb 2024. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Iran. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
Results are not available in the source record.
How can a doctor refer a patient or contact the research team?
Contact Ali Moghimi, PhD (0098 09153176390, moghimi@um.ac.ir), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Disgust Feeling (time frame: From pre- to post-assessment (2 weeks after baseline assessment) and from pre- to follow-up assessment (10 weeks after baseline assessment)). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT05907369, which also lists 2 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 28 Feb 2024; AzTrials last refreshed its copy on 30 Oct 2026.