Postpartum psychosis is a rare but severe psychiatric disorder. Its diagnostic status remains controversial, but several studies have shown that the majority of patients who develop psychosis immediately following childbirth suffer from bipolar disorder. The pathophysiology of postpartum psychosis is poorly understood, but factors such as primiparity, difficult labor, genetic predisposition, and hormonal changes have been suggested as etiological factors. This paper reviews the literature on the relationship of sleep disruption and postpartum psychosis. It is argued that sleep loss resulting from the interaction of various putative causal factors may be the final common pathway in the development of psychosis in susceptible women. Clinical significance of these findings, including strategies to prevent postpartum psychosis, are discussed and suggestions are made for future research directions.