Neural-Derived Plasma Exosomal MicroRNAs As Promising Novel Biomarkers for Suicidality and Treatment Outcome in Adolescents

This study is looking at whether specific molecules found in blood plasma — called microRNAs from nerve-derived particles — can serve as early markers to predict suicidal thoughts, suicide attempts, and treatment outcomes in teenagers with depression. The goal is to develop a blood test that could help clinicians identify at-risk young people. **You may be eligible if:** - You are physically healthy and willing to provide consent (and parental consent if under 18) - You are a teenager with a diagnosis of major depressive disorder (MDD), OR you have had suicidal thoughts or a recent suicide attempt requiring medical attention, OR you are a healthy teenager with no history of mental illness **You may NOT be eligible if:** - You have a health condition that would make participation unsafe - (Healthy controls) You have any history of a major mental illness or substance use disorder Talk to your doctor to see if this trial is right for you.