Premenstrual syndrome (PMS) is a group of symptoms linked to the menstrual cycle. These symptoms include mood swings, bloating, acne, tender breasts, food cravings, fatigue, headache, irritability and depression. It's estimated that as many as three of every four menstruating women have experienced some form of PMS. Symptoms may start a week or two before the period and can be mild to severe. Changes in hormones during the menstrual cycle seem to be an important cause; chemical changes in the brain may also be involved. Stress and emotional problems do not seem to cause PMS, but they may make it worse. About 3 to 8 percent of women have a more severe form of PMS, called premenstrual dysphoric disorder (PMDD), which can be debilitating. The good news is that if you improve your diet, manage stress and implement natural remedies, you can experience significant improvements in the symptoms associated with PMS.