Multiple lines of evidence suggest that both genetic factor and environmental factor are associated with the onset of depression. Cohort studies are necessary for comprehensive investigation of interaction between genetic and environmental factor. However, in these studies, it is usually difficult to identify the stressor that may be important for of development of symptoms. This problem is less prominent in the study of if the postpartum depression where the relationship between stressor (i. e. pregnancy and childbirth), and development of the symptoms has already been established. Postpartum depression is suicide risk factor and affects mother’s Quality of life (QOL). In addition, maternal depression have a bad influence on the new- born child. Therefore, it’s imperative to establishment of an effective prevention and treatment protocols. In order to address these issues, we are performing prospective genome cohort study focused the pregnant woman who consulted obstetric service. At this point we have collected data from more than 600 women and we are expanding the number of participants In this article, we discuss the importance of the genome cohort study in depression research, and introduce a some of the data from our current research.