Premenstrual syndrome (PMS) is a set of emotional and physical symptoms that regularly occur in the one to two weeks before menstruation begins. Common symptoms include breast tenderness, bloating, headaches, and mood swings like depression and irritability. PMS is caused by fluctuations in hormones like progesterone and estrogen as well as other factors like genetics, stress, and chemical changes in the brain. Treatment options include antidepressants, anti-inflammatory drugs, diuretics, birth control, and supplements like calcium, vitamin B6, and magnesium.