RecruitingClinical trialPrediction of REsponse to Depression Interventions (Accelerated rTMS) Using Clinical and TD-fNIRS MeasurementsThis observational, longitudinal, multi-cohort study aims to evaluate functional brain activity in adults undergoing treatment for Major Depressive Disorder (MDD) at participating clinical sites. A separate cohort of healthy adults will be enrolled as a control group. All data collected in this study are for research purposes only and will not influence clinical decision-making or treatment plans. This study will use TD-fNIRS to measure hemodynamic brain responses at rest and/or during tasks in patients receiving accelerated transcranial magnetic stimulation (TMS). Imaging will occur at multiple timepoints (pre-treatment, post-treatment, and follow-ups). Healthy control participants will complete similar measurements at one visit, with the option for a follow-up visit. The primary objectives are to assess feasibility, characterize brain activity patterns, and explore potential biomarkers associated with treatment response.