Premenstrual syndrome (PMS) is a disorder marked by physical and behavioral symptoms that occur in a cyclical pattern. They appear a week or two before an expected menstrual period and improve with the onset of menses. The nature and severity of symptoms vary. If your symptoms are so severe that they interfere with daily activities, talk to your doctor about treatment options.

Many women of reproductive age have discomfort prior to menses, but a small number cases are thought to be categorized as PMS. This problem is most commonly seen between the ages of 25-34. An even smaller percentage of women with PMS have a very severe form called premenstrual dysphoric disorder (PMDD).

Although the cause of PMS is not known, the cyclical pattern that parallels the menstrual cycle has directed the focus of study to hormonal changes. These changes are thought to act with other factors in the nervous system, as well as the environment, to trigger the symptoms of PMS.

Last Reviewed September 2012