Most of the studies on paternalPPD have been done by using selfreport questionnaires. Studies onhormonal and physiological changesduring the postpartum period amongfathers would provide information onbiological factors of depression andbiological mechanisms of fatherinfant attachment. In addition, brainimaging studies of paternal PPD willenrich our understanding of differentbrain circuits and neurohormonalsystems that govern the processes ofparenting in health and, in particular,among fathers with PPD