As its Latin name cardiaca suggests, motherwort has traditionally been used to treat heart conditions. The ancient Greeks and Romans employed motherwort to treat heart palpitations as well as depression, which they considered a problem of the heart. Centuries later, Europeans would believe motherwort helpful for "infirmities of the heart" but also considered the herb to have strengthening and stimulating effects on the uterus, using it to bring on a delayed menstrual period, as an aid during labor, and to relax a woman's womb after childbirth.

These uses of motherwort correspond well with those in traditional Chinese medicine, which employs the Asian variety, Leonurus artemisia, to treat menstrual disorders or to help a woman expel a dead fetus and placenta from her womb.1In eastern China, women still drink a syrup made from motherwort to promote the recovery of the uterus after childbirth; the herb has a strong bitter taste, so visitors to a recovering mother often bring along sugar as a gift.2

Germany's Commission E has authorized motherwort for the treatment of rapid or irregular heatbeat caused by anxiety and stress, as well as part of an overall treatment plan for an overactive thyroid ( hyperthyroidism, a condition that also causes irregualr heartbeat).3

However, as yet there is no real evidence to support these uses of the herb. The best that can be said is that in one test tube studymotherwort slowed the beating of normal rat heart cells and inhibited the effects of substances that usually speed up heart cell contractions.4

Two other test tube studies suggest that leonurine, a compound found in some species of motherwort, may affect the uterus.5,6One of these studies found that low concentrations of leonurine induced uterine contractions, but that higher concentrations inhibited contractions.7 These opposing effects might explain how motherwort could induce both labor and menstruation, and yet could also relax the uterus after childbirth (as it is traditionally said to do). However, until properly designed human studies are performed, we won't have any clear idea whether motherwort is actually safe or effective for these traditional uses.

One poorly designed study suggests that motherwort might improve blood circulation.8 Another study of equally low quality hints that motherwort might protect brain tissue in people who have had a stroke.9

One component of motherwort, ursolic acid, has been found to possess possible antiviral and antitumor properties; however, this extremely preliminary preliminary information should not be taken to mean that motherwort can fight viral infections or help treat cancer.10,11