Bipolar Proteomic Assay Validation Study

Inclusion Criteria: * Diagnosed with BDI, BDII, or MDD, confirmed with the Structured Clinical Interview for DSM-5 (SCID). * Currently depressed for ≥4 weeks and ≤104 weeks, without psychotic features, * MADRS score ≥ 20 (consistent with at least moderately-severe depression) * YMRS score ≤ 8 (consistent with the absence of hypomanic symptoms) Exclusion Criteria: * At high risk for suicide, defined as a score ≥4 on item 10 of the MADRS * Current depression has psychotic features, diagnosed with the SCID * Meeting criteria for severe alcohol, cannabis, or THC use disorders, as defined by DSM-5 and confirmed by the SCID, in the past 3 months, or meeting criteria for other substance use disorders of any severity (eg. cocaine use disorder). For substances other than alcohol, cannabis, and opioids, a positive drug screen at both the screening and baseline visits is also exclusionary. Caffeine and nicotine use disorders of any severity will not be exclusionary. * Diagnosis of borderline personality disorder, diagnosed with the Zanarini Rating Scale for Borderline Personality Disorder. * Medical conditions with neurological sequelae (eg. stroke, brain cancer, multiple sclerosis, loss of consciousness \> 30 min, HIV) * Severe chronic pain, at the discretion of the investigator * Receiving treatment with high-potency immune-modulating medications, such as corticosteroids, chemotherapy, monoclonal antibodies, or disease-modifying agents for arthritis, multiple sclerosis * Any acute unstable medical illness (at the discretion of the site investigator) * In MDD patients: strong risk factors for bipolarity, including 1) short (1-3 day) mood elevations not meeting DSM-5 time criteria for hypomania; 2) a family history of BDI or BDII in a first-degree relative; and 3) a history of antidepressant-induced symptoms suggestive of bipolarity, particularly antidepressant-induced hypo/mania.