Premenstrual syndrome, or PMS, occurs in women before their menstrual cycles. Normal premenstrual symptoms in women include bloating, uterine cramping, headaches, tender breasts, sleep problems, low sex drive, lower back discomfort, constipation, and weight gain. Normal symptoms of PMS will also have some mood and behavioral symptoms. These PMS symptoms include low mood, irritability, anxiousness, decreased alertness, and withdrawal from family and friends. All normal PMS symptoms should not be severe or long-lasting enough to significantly impact the quality of a woman’s life. PMS occurs in the second half of the menstrual cycle, between ovulation and the beginning of menstrual bleeding. For many women, there will be a difference between cycles in the quantity of menstrual blood and the severity of PMS symptoms.