Neurochemical Effects of Omega-3 Fatty Acids in Adolescents at Risk for Mania

The purpose of this study is to see if taking a substance called omega-3 fatty acids is effective, safe, and well-tolerated for treating adolescents with major depressive disorder (also called simply "depression" or "clinical depression"). Another purpose of this study is to see how much omega-3 fatty acids are in a patient's blood and if that makes the patient more or less likely to develop mania (i.e. periods of irritability or extreme silliness accompanied by decreased need for sleep, risky behaviors, feeling like the patient has special abilities, inability to sit still, and rapid speech) in the future. Yet another purpose of this study is to see how taking omega-3 fatty acids affect brain scans. Omega-3 fatty acids are not United States Food and Drug Administration (FDA)-approved to treat depression in adults or in children and adolescents. Omega-3 fatty acids can only be obtained through diet, most often from fish and other sea foods, though they are also found in other food sources such as flax seed. Omega-3 fatty acids have been shown to play a role in affecting brain chemicals responsible for regulating mood and have been found to reduce symptoms of depression in medicated-patients with major depressive disorder. By completing this study, the investigators hope to better understand who benefits from treatment, why they do or do not respond to medications, and who is at greater risk for developing further mental illness. With this information, the investigators hope to be able to improve treatment and outcome in people with major depressive disorder.