Premenstrual syndrome, or PMS, is a group of unpleasant symptoms linked to a woman's menstrual cycle, typically occurring one to two weeks before the menstrual period begins. PMS symptoms vary widely among women and range in severity from mild to debilitating. PMS typically includes physical and emotional symptoms. Some of the most common symptoms of PMS include abdominal pain, mood changes, tiredness, anxiety, headache, backache, depression, bloating, and constipation or diarrhea. Other symptoms often reported are joint pain, sleep disturbances, appetite changes, food cravings, tension, crying spells, and tenderness or pain in the breasts. Sometimes women who suffer from PMS note that they have difficulty concentrating or problems with memory when symptoms are present.