Brain scans reveal new clues to Depression's inner workings

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria for all participants: * All genders, races, and ethnic origins, aged between 18 and 45 * Capable of providing written informed consent, and fluent in English * Right-handed * Absence of any psychotropic medications for at least 2 weeks * Has a smartphone (iPhone or Android) (needed for Ecological Momentary Assessment) Inclusion Criteria for "Remitted MDD" group: * Meets inclusion criteria for all subjects, plus: * History of MDD as defined by DSM-5 * Absence of anxiety disorder for the past two months Inclusion Criteria for "Current MDD" group: * Meets inclusion criteria for all subjects, plus: * Presence of MDD as defined by DSM-5 * Absence of anxiety disorder for the past two months Exclusion Criteria for all participants: * Subjects with suicidal ideation where outpatient treatment is determined unsafe by the study clinician. These patients will be immediately referred to appropriate clinical treatment * Pregnant women or women of childbearing potential who are not using a medically accepted means of contraception (defined as oral contraceptive pill or implant, condom, diaphragm, spermicide, IUD, s/p tubal ligation, or partner with vasectomy) * Serious or unstable medical illness, including cardiovascular, hepatic, renal, respiratory, endocrine, neurologic or hematologic disease * History of seizure disorder * History of psychiatric illnesses, other than depression or anxiety disorders among the Current MDD and Remitted MDD groups * History of substance use disorder or alcohol use disorder (as these terms are defined by DSM-5); except depressed subjects may have a history of 'Mild' substance/alcohol use disorder only if it ended as least 12 months ago * History of cocaine or stimulant use or dopaminergic drugs * History or current diagnosis of dementia, or a score of \< 26 on the Mini Mental State Examination at the screening visit; * Patients with mood congruent or mood incongruent psychotic features * Current use of other psychotropic drugs * Clinical or laboratory evidence of hypothyroidism * Patients with a lifetime history of electroconvulsive therapy (ECT) * Failure to meet standard MRI safety requirements * Abnormal ECG and lab results * History of seizure disorder * Contraindications for arterial line (e.g., abnormal result on Allen test, Raynaud's syndrome, history of anemia or bleeding disorder, history of fainting from blood draws).