Premenstrual syndrome (PMS) is characterized by emotional and physical symptoms that can be troubling and cause moderate discomfort for women the week or two before the onset of their menstrual cycle. PMS is estimated to affect up to 40 percent of reproductive-aged women. Approximately 5 to 10 percent of these women experience symptoms so severe that it totally impairs their everyday . This severe form of PMS is known as premenstrual dysphoric disorder (PMDD). The precise of PMS is still unknown; however, it is increasingly believed that the sensitive equilibrium between female sex (the and progesterone) and in the brain is altered in women with PMS.