Premenstrual syndrome (PMS) is a term used to describe a wide range of recurrent symptoms many women experience in the two weeks before menstruation (the luteal phase). Symptoms may be mild or severe. They are physical, emotional or behavioral and usually stop when menstruation begins, or shortly thereafter.

PMS can appear at any time between puberty and menopause. Symptoms usually recur in a predictable pattern, but may worsen with age or stress. PMS often increases during times of hormonal turbulence, such as puberty, after childbirth, after miscarriage or abortion and with changes that may occur with contraception use.

PMS is common among women of childbearing age. Most women experience some of the symptoms associated with PMS at some point in their lives, but not all women have the syndrome. Estimates of the exact percentage of women that have PMS vary widely. According to the National Institutes of Health, an estimated 75 percent of menstruating women experience some form of PMS.

A smaller percentage (less than 10 percent) of women experience symptoms so severe that it disrupts their daily lives. This more severe condition is called premenstrual dysphoric disorder (PMDD). Patients with this disorder are diagnosed under stringent guidelines issued by the American College of Obstetricians and Gynecologists (ACOG).

Although it was first identified in 1931, PMS remains a poorly understood condition because there are differing opinions about its cause, diagnosis and treatment. PMS is a syndrome, meaning that it is a group of related symptoms, but has no known cause. As such, management of PMS focuses on alleviating these symptoms rather than curing their underlying cause.