Additional Study Information: This research study uses brain imaging to explore the biological causes of major depression and why it sometimes causes suicidal thinking. We hope to improve treatment and prevention. You may qualify if you have depression with or without suicidal thoughts or suicide attempts. Participation involves detailed interviews, blood and hair sampling, brain imaging scans and a stress test (measuring the bodys response to stress during brief arithmetic and speech tasks). Eligible individuals will be compensated up to $1,350. We seek to minimize COVID-19 risk, by doing clinical assessments via televideo to minimize visits to the medical center. All standard safety precautions are employed to keep you as safe as possible at all times in this study.