Electrophysiological Biomarkers and Treatment Response to Accelerated Transcranial Magnetic Stimulation in Patients With Obsessive-Compulsive Disorder (TMS-OCD-EEG)

May 7, 2026 updated by: Sarp Yoldas, Istanbul University - Cerrahpasa

Investigation of the Relationship Between Electrophysiological Biomarkers and Treatment Response in Patients Diagnosed With Obsessive-Compulsive Disorder Undergoing Transcranial Magnetic Stimulation Therapy

Purpose:

This study aims to evaluate the effectiveness of an accelerated intermittent Theta Burst Stimulation (iTBS) protocol-a non-invasive brain stimulation technique-targeted at the dorsomedial prefrontal cortex (dmPFC) and anterior cingulate cortex (ACC) in patients with treatment-resistant Obsessive-Compulsive Disorder (OCD). Additionally, the study seeks to identify electrophysiological biomarkers (such as EEG microstates and heart rate variability) that may predict which patients are most likely to benefit from the treatment.

Methodology:

The study will include 30 patients aged 18-65 diagnosed with OCD according to DSM-5 criteria who have not responded sufficiently to standard treatments. Participants will undergo an intensive 7-day treatment program consisting of 4 iTBS sessions per day (totaling 28 sessions). Clinical symptoms will be assessed before and after the treatment using standardized scales, including the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), Hamilton Depression Rating Scale (HAM-D), and Hamilton Anxiety Rating Scale (HAM-A). Resting-state EEG measurements and heart rate data will be recorded during and after the sessions to analyze physiological changes.

Goal:

The findings are expected to contribute to the development of personalized neuromodulation protocols and help identify predictors of treatment response for OCD patients.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

30

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • Turkey (Türkiye)
    • Bakirkoy
      • Istanbul, Bakirkoy, Turkey (Türkiye), 34153
        • Recruiting
        • Cerrahpaşa Tıp Fakültesi Prof. Dr. Murat Dilmener Hastanesi
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Being between 18 and 65 years of age.
  • Being diagnosed with Obsessive-Compulsive Disorder (OCD) according to DSM-5 criteria.
  • Non-responsiveness to at least one Selective Serotonin Reuptake Inhibitor (SSRI) treatment at an adequate dose and duration.
  • Having a Y-BOCS score of ≥20 following the initial evaluation.
  • No change in the current medications within the last 2 months and a commitment to maintaining stable doses throughout the study.
  • Providing informed consent and having no contraindications for TMS.

Exclusion Criteria:

  • Severe neurological disorders or neurodegenerative diseases.
  • Any condition associated with increased seizure risk
  • History of cochlear implants, metal implants in the head and neck area, cardiac pacemakers, deep brain stimulation, or vagus nerve stimulation.
  • History of neurosurgical intervention.
  • General contraindications for Transcranial Magnetic Stimulation therapy.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: TMS Treatment Arm
Device: iTBS TMS

Accelerated intermittent Theta Burst Stimulation (iTBS) will be delivered using a MagVenture MagPro R30 stimulator with a Cool D-B80 double cone coil. The stimulation is targeted at the dorsomedial prefrontal cortex (dmPFC) and anterior cingulate cortex (ACC), specifically 25.8% anterior of the nasion-inion distance. The treatment will be applied at 100% of the motor threshold, which is determined via the Extensor Hallucis Longus muscle.

The protocol consists of an intensive 7-day program with 4 sessions per day, totaling 28 sessions. Each session delivers 1,800 pulses and lasts approximately 9 minutes. Patients will continue their stable dose of Selective Serotonin Reuptake Inhibitors (SSRIs) throughout the study.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) Total Score
Time Frame: Change from baseline in clinical scales at the end of the 7-day treatment and at follow-up points (1, 3, and 6 months post-treatment)"
The Y-BOCS is a 10-item clinician-administered scale used to assess the severity of obsessive-compulsive symptoms. Each item is rated from 0 to 4. The total score ranges from 0 to 40, where higher scores indicate greater symptom severity (32-40: extreme, 24-31: severe, 16-23: moderate, 8-15: mild, 0-7: subclinical).
Change from baseline in clinical scales at the end of the 7-day treatment and at follow-up points (1, 3, and 6 months post-treatment)"

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
EEG Microstate Analysis Parameters
Time Frame: Baseline, Day 7 (after treatment)
Resting-state EEG data will be analyzed using the MICROSTATELAB v2.1 extension for EEGLAB focusing on the four canonical microstate classes labeled A, B, C, and D. For each participant, four specific spatio-temporal parameters will be calculated to evaluate neural dynamics. These include Mean Duration which measures the average lifespan of a specific microstate in milliseconds to represent the stability of neural generators, and Occurrence which measures the average frequency of each microstate per second in Hz to reflect activation tendencies. Additionally, Time Coverage will be calculated as the percentage of total analysis time during which a specific class is dominant, and Transition Probability will be determined to show the likelihood of one microstate class transitioning into another, providing insight into the sequential activation dynamics of the underlying neural networks.
Baseline, Day 7 (after treatment)
Frontal-Vagal Activity via Heart Rate Deceleration (HRD)
Time Frame: During each of the 28 iTBS sessions over the 7-day treatment period
Heart rate data will be recorded using a Polar H10 sensor during iTBS sessions. HRD will be calculated as the change in heart rate (beats per minute - bpm) during the stimulation period compared to the pre-stimulation baseline. Lower heart rate (greater deceleration) is investigated as a predictor of higher fronto-vagal activation and treatment response.
During each of the 28 iTBS sessions over the 7-day treatment period

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Istanbul University - Cerrahpasa

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

January 1, 2026

Primary Completion (Estimated)

February 1, 2027

Study Completion (Estimated)

April 1, 2027

Study Registration Dates

First Submitted

April 26, 2026

First Submitted That Met QC Criteria

April 26, 2026

First Posted (Actual)

May 1, 2026

Study Record Updates

Last Update Posted (Actual)

May 8, 2026

Last Update Submitted That Met QC Criteria

May 7, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 1395891
  • 38661 (Other Grant/Funding Number: İstanbul Üniversitesi-Cerrahpaşa Rektörlüğü, Bilimsel Araştırma Projeleri)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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