Additional Study Information: This NIH-funded research study uses brain imaging to explore the biological causes of major depression and suicide. We hope to develop a better understanding of how people who feel depressed and suicidal cope with their feelings so we can improve treatment and prevention. You may qualify as a healthy control if you do not have psychiatric illness. Participation involves a set of diagnostic interviews, brain imaging scans (MRI and PET) and neuropsychological tasks. Eligible individuals will be compensated up to $750. If you also sign up for our companion behavioral study, you could receive up to $1,250. Our rigorous safety protocols minimize the risk of COVID-19 exposure.