Though it may be surprising, cramps are not typically associated with PMS. Painful periods, known as dysmenorrhea, are quite they are caused by uterine contractions, which is how the expels the endometrial lining. In other words, the uterus contracts order to shed the endometrial lining and thus causes cramps.

In contrast, premenstrual syndrome is related to hormone and may be aggravated by vitamin and mineral deficiencies, depressive disorders, stress, and multiple psychological disturbances. A woman can have primary dysmenorrhea, which means there is no underlying cause for the pain, or secondary dysmenorrhea, in which pain is caused by another medical condition such as endometriosis or fibroids.

Many women experience cramping during their periods without the bloating, depression, anxiety, or headaches that are more common to PMS. Some women are more disposed to cramping simply because their uterus contracts more than the next woman’s. Cramps may also be related to low levels of calcium. Experts believe that prostaglandins, which are hormone-like substances involved in pain and inflammation, may trigger menstrual cramps. (Chapters 5, 6, 7, and 18 also discuss prostaglandins.) Women with PMS may or may not experience cramps.