We are conducting a research study that aims to understand why some women develop postpartum depression or psychosis and others do not. The research is designed to test the idea that a genetic variation together with folate levels in a woman's blood can influence her risk for postpartum depression. The aim of the research is to find ways to help to reduce the risk for postpartum depression by using nutritional supplements. Women who are pregnant (at any stage of pregnancy) and who have a history of mental health problems are being recruited to participate in the study. The study involves a participant meeting with a researcher 4 times: once during the pregnancy, and 3 times over the first 3 months of the postpartum period. The researchers can cover costs of travel for women to participate in the research at either St. Paul's or Children's and Women's Hospitals. Alternatively, some study visits can be conducted at participants' homes or by email/phone. If you are interested in participating, please contact Jennifer Sloan at: 604.875.2000 ext.  4733 or by email at mental.illness@ubc.ca