Anxiety & Depression Association of America

for: Accelerated TMS cohort - Adults aged 18-75 at the time of enrollment - Primary diagnosis of MDD as defined by the DSM-5 - Determined by the clinic to be eligible for accelerated rTMS treatment and agrees to receive accelerated rTMS treatment - Agrees to start accelerated rTMS treatment in conjunction with study participation to capture baseline measurements - Has not received rTMS treatment in the past 1 month - Has not received SPRAVATO treatment in the past 1 month - Can speak and understand English - Ability to provide informed consent Healthy controls cohort - Adults aged 18-75 at time of enrollment - Can speak and understand English - Ability to provide informed consent

for: All cohorts - Pregnant or may become pregnant during the treatment course - Unable or unwilling to wear the fNIRS headset - Has had electroconvulsive therapy (ECT) in the past 3 months - Major medical illnesses including neurological and psychiatric conditions such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, epilepsy, schizophrenia, or stroke. - Any other clinically significant medical condition that in the opinion of the clinician or study team, could affect patient safety, wellbeing, or the participant's ability to comply with study procedures. - Not an appropriate candidate for the study based on the discretion of the study investigator(s). Healthy controls cohort only - Clinical diagnosis of depression in the past year - Undergoing any treatments for depression in the past year