The goal of this clinical trial is to learn how different types of non-invasive brain stimulation affect mood and brain function in adults with major depressive disorder (MDD). It will also study how brain stimulation may work together with antidepressant treatments.

The main questions this study aims to answer are:

How do different patterns of brain stimulation affect mood in people with depression?

Do brain networks involved in emotion and self-reflection respond differently depending on the type of stimulation?

What are the combined effects of brain stimulation and antidepressant treatments on mood and brain activity?

Researchers will compare different brain stimulation patterns and target areas to understand their individual and combined effects.

Participants will:

Receive three types of brain stimulation (intermittent, continuous, and sham) in different sessions

Undergo MRI scans during the administration of either a fast-acting or conventional antidepressant.

Complete mood assessments during the scan and for one week after each session

This study may help identify brain-based strategies to improve treatment for depression.

In addition, a subset of participants (~10) will complete a reward-guided decision-making fMRI task for feasibility purposes.

This mechanistic clinical trial will investigate the role of large-scale brain networks in modulating mood responses in adults with major depressive disorder (MDD) using non-invasive neuromodulation and neuroimaging. The study will focus on the salience network (SN), default mode network (DMN), and functional connectivity (FC) between them, given prior evidence linking these systems to mood regulation and antidepressant response.

Using a 2x3 factorial design, 200 participants with MDD will be randomized to receive theta burst stimulation (TBS) targeting either the SN or the DMN (between-subject factor). Each participant will complete three within-subject TBS sessions one week apart: intermittent TBS (iTBS), continuous TBS (cTBS), and sham stimulation. TBS will be delivered over individualized fMRI-based targets derived from prior resting-state connectivity maps.

Following each stimulation session, participants will complete an MRI protocol that includes administration of either a fast-acting or conventional antidepressant, as well as resting-state functional imaging. In addition, a subset of participants (~10) will complete a reward learning fMRI task, a reward-guided decision-making, designed to capture value-based decision-making processes.

Primary neural outcomes include changes in activation and connectivity within and between SN and DMN regions, measured using task-based and resting-state fMRI. Behavioral outcomes include mood ratings acquired repeatedly during the scanning session and via daily remote assessments for one week post-stimulation.

This design allows for within-subject comparison of the acute and sub-acute effects of different TBS patterns, and between-subject comparison of SN- vs. DMN-targeted stimulation. The study aims to identify brain circuits that can be engaged or modulated to enhance treatment response in depression, with the longer-term goal of informing precision neuromodulation strategies.

Note: Certain information is withheld to protect the scientific integrity of the study design.

Inclusion criteria:

1. Adults ages 18-55 (~60% female).
2. Diagnosis of Major Depressive Disorder (MDD) with or without comorbid anxiety disorders (e.g., panic disorder) or Axis II disorders.
3. Psychotropic-free at enrollment.

Exclusion Criteria:

1. being pregnant or breastfeeding;
2. diagnosis of psychotic depression, schizophrenia, bipolar disorder, or other Axis I disorders, except for anxiety disorders;
3. severe substance use (excluding nicotine) in the last 2 months as determined by using the MINI, a structured interview that uses the Diagnostic and Statistical Manual of Mental Disorders;
4. requiring immediate hospitalization;
5. epilepsy or conditions requiring an anticonvulsant;
6. receiving vagus nerve stimulation, electroconvulsive therapy (ECT), or TMS in the last 2 months;
7. currently taking or have taken within the last 21 days psychiatric medication or augmenting agents;
8. receiving depression-specific psychotherapy;
9. actively suicidal or considered a high suicide risk;
10. enrolled in another study; or
11. MRI/TMS contraindication as determined by the fMRI and TMS screening questionnaires

Consistent with NIMH Data Archive (NDA) policies, the investigators will obtain relevant GUIDs and experiment IDs in order to upload all relevant data biannually. The investigators will use the Validation and Upload Tool for CSV files from behavior during the fMRI experiment, and NIfTI-formatted images for imaging. The investigators will upload study data cumulatively every 6 months per NDA guidelines, with the exception of imaging data, which are will be uploaded in installments.

The final research data will not contain any identifiable information and will be deposited in the NIMH Data Archive (NDA). While data is submitted biannually, the complete dataset will be made available for sharing with the research community 24 months after the original study end date. Furthermore, the specific data used for primary analyses will be shared via an NDA Study DOI prior to the acceptance for publication of the main findings.

Supporting documentation, including the Study Protocol, Statistical Analysis Plan, Informed Consent Form, and Analytic Code, will be made available upon reasonable request from the journal or other investigators. Furthermore, analytic code and study protocols will be provided as supplemental material at the time of publication of the main findings as deemed appropriate.

Anyone who wishes to access the data.