Clinical Research Directory

Inclusion Criteria: * Patients diagnosed with Major Depressive Disorder as certified by a SCID 5 (Structured Clinical Interview for DSM-5) for DSM-S for adults and K-SADS-PL-DSM 5 (Kiddie Schedule for Affective Disorders and Schizophrenia - Present and Lifetime for DSM 5) for adolescents. * Currently experiencing a major depressive episode with a HAM-D (Hamilton Depression) score of 18 or greater, or alternatively, a MADRS (Montgomery-Asberg Depression Rating Scale) score of 18 or greater. * About to start a new antidepressant. * Not concurrently starting a new psychotropic medication. * Age 14-50 years. * Able to use mobile devices (smart phone, tablet). * Willingness to provide written informed consent to participate. Exclusion Criteria: * Intellectual disability. * Neurological disease (multiple sclerosis, severe neurocognitive disorder, epilepsy). * Current psychotic disorder or mood disorder with psychotic features. * Primary diagnosis of alcohol or substance use disorder (DSM-5). * Patients who started concomitant psychotropic medications less than one week ago. * Active, ongoing inflammatory diseases (such as rheumatoid arthritis and rheumatic polymyalgia). or severe and unstable physical illness (such as recent myocardial infarction). * A history of hepatitis B or C, human immunodeficiency virus, or evidence of active tuberculosis infection or any active systemic infection within 2 weeks prior to the start of the study. * Use of antibiotics or other medications that may have affected the composition of the microbiota during the 30 days prior to baseline. * Pregnancy and lactation.