Repetitive transcranial magnetic stimulation (rTMS) has emerged as a promising intervention for treatment-resistant depression (TRD), yet substantial uncertainties persist regarding its efficacy as a maintenance treatment. This prospective study seeks to investigate the efficacy of maintenance rTMS in individuals with TRD who have previously responded to an acute course of rTMS. In the R61 phase of the study, we will recruit 75 participants across three study sites, the University of California San Diego, Weill Cornell Medicine, and Australian National University, into a double-blind, three-arm maintenance treatment trial. In this trial, participants will be randomized to receive either standard maintenance rTMS, clustered maintenance rTMS, or sham maintenance rTMS for a duration of 6 months. Our primary aim is to examine the efficacy of maintenance rTMS on sustaining connectivity between the dorsolateral prefrontal cortex (DLPFC) and subgenual cingulate cortex (SGC) measured through concurrent TMS and electroencephalography (TMS-EEG) at baseline and every six weeks throughout the 6-month treatment period. We will also assess changes in depressive symptom severity using clinical scales, including the Montgomery-Asberg Depression Rating Scale (MADRS) as a secondary outcome measure. It is hypothesized that stimulation with clustered maintenance rTMS will demonstrate superiority in sustaining DLPFC-SGC connectivity compared with standard maintenance rTMS and sham maintenance rTMS

Inclusion Criteria:

1. They met criteria for a DSM-5 diagnosis of a Major Depressive Episode (MDE) during the index episode of depression for which they have received an acute rTMS treatment course.
2. Meet criteria for either response or remission from their initial depressive illness. The MINI assessment timeline will be adjusted to allow scoring of illness symptoms prior to rTMS response. Response to acute course of treatment is defined as either a MADRS score of <10, or a MADRS score of 10-19, plus evidence of having met response criteria on either the MADRS or another structured depression rating scale. The response is defined as a >50% reduction in the total score from the start to the end of treatment.
3. Their initial rTMS treatment course must have consisted of at least 15 rTMS treatment sessions.
4. People between the ages of 18 and 80 at the time of screening. A written statement from the referring physician will be required to confirm that the participant demonstrates the capacity to consent.
5. Able to read, understand, and provide written, dated informed consent prior to screening. Proficiency in English sufficient to complete questionnaires / follow instructions during TMS-EEG assessments and iTBS interventions. Stated willingness to comply with all study procedures, including availability for the duration of the study, and to communicate with study personnel about adverse events and other clinically important information.
6. In good general health, as evidenced by medical history.
7. Agreement to adhere to Lifestyle Considerations throughout study duration.
8. If a person of child-bearing potential is: must take a pregnancy test at the screening visit, with results confirmed as negative by study staff

Exclusion Criteria:

• 1. Pregnancy 2. History of or current psychotic disorder or depression with psychotic features 3. Severe borderline personality disorder based on clinical assessment. 4. Diagnosis of Intellectual Disability or Autism Spectrum Disorder 5. Current moderate or severe substance use disorder or demonstrating signs of acute substance withdrawal 6. Clinically significant suicidal ideation with plan 7. Any history of ECT (greater than 8 sessions) without a clinical meaningful response in the current episode.

  8. Recent (during the current depressive episode) or concurrent use of rapid-acting antidepressant agent (i.e., ketamine or a course of ECT) in the last 30 days 9. History of significant neurologic disease, including dementia, Parkinson's or Huntington's disease, brain tumor, seizure disorder, subdural hematoma, multiple sclerosis, or history of significant head trauma 10. Untreated or insufficiently treated endocrine disorder. 11. Contraindications to receiving rTMS (e.g., metal in head, history of seizure, known brain lesion) 12. Treatment with an investigational drug or other intervention within the study period 13. The patient experiences a relapse between baseline and screening, defined as a moderate depression (MADRS >=20) and a 25% increase from screening to baseline 14. Require a benzodiazepine with a dose > lorazepam 2 mg/day or equivalent or any anticonvulsant (with the exception of Gabapentin, pregabalin, and lamotrigine).