DefinitionPremenstrual syndrome (PMS) refers to a wide range of physical or emotional symptoms that typically occur about 5 to 11 days before a woman starts her monthly menstrual cycle. The symptoms usually stop when menstruation begins, or shortly thereafter.See also: Premenstrual dysphoric disorder (PMDD)Alternative NamesPMSCauses, incidence, and risk factorsThe exact cause of PMS has not been identified. Changes in brain hormone levels may play a role, but this has not been proven. Women with premenstrual syndrome may also respond differently to these hormones.PMS may be related to social, cultural, biological, and psychological factors.The condition is estimated to affect up to 75% of women during their childbearing years.It occurs more often in women:Between their late 20s and early 4