Additional Study Information: This research study uses brain imaging to explore the biological causes of depression and of suicidal behavior. Suicidal behavior and major depression are transmitted in families. Some family members are at risk and others are resilient. We hope to develop a better understanding of how those family members at risk differ from those who are resilient. We hope to figure out how to make those at risk more like those who are resilient. This is real prevention because we want to prevent people from ever becoming depressed in the first place. Participation involves a detailed diagnostic set of interviews, brain imaging scans (MRI and PET) and neuropsychological tasks. Eligible individuals will be compensated up to $475.