Mood disorders, such as depression and bipolar disorder, are difficult to treat. One reason is that there are no objective ways to measure how these disorders affect the body and respond to different treatments. In this study, researchers want to perform tests on people undergoing clinical care for mood disorders. The purpose is to understand the experience of receiving treatment for depression, bipolar disorder, and suicide risk. We also hope that this study will help us to predict which medications will improve thoughts of suicide. People 18 years or older who are receiving treatment for depression, bipolar disorder, or suicide risk may take part in this study. Participants must have also been enrolled in protocol 01-M-0254. This study will be conducted at the NIH Clinical Center in Bethesda, MD. The study typically lasts up to 12 weeks, but may last longer if a participant s treatment continues past that time. Participants will have weekly interviews and questionnaires while they are being treated for their mood disorder. Other tests are optional and include psychological testing, blood draws, sleep tests, and imaging scans. These will be done at the start and the end of research participation.