St. John’s Wort

Background

• St. John’s wort is a plant with yellow flowers that has been widely used in various systems of traditional medicine, including Greek, Islamic, and Chinese medicine. The name St. John’s wort apparently refers to John the Baptist, as the plant blooms around the time of the feast of St. John the Baptist in late June.
• Historically, St. John’s wort has been used for a variety of conditions, including depression, stomach ulcers, and colds, and to aid wound healing.
• Currently, St. John’s wort is most widely promoted for symptoms of depression. It is also promoted for menopause symptoms and other conditions. Topical use (application to the skin) of St. John’s wort is promoted for wounds and other skin conditions.

How Much Do We Know?

• Many studies have been done on the usefulness of St. John’s wort for depression, and their results indicate that it may be helpful for mild or moderate depression. For other conditions, the evidence is insufficient to allow definite conclusions about the usefulness of St. John’s wort to be reached.
• It has been clearly shown that St. John’s wort can interact in dangerous, sometimes life-threatening ways with a variety of medicines.

What Have We Learned?

• St. John’s wort appears to be more effective than a placebo (an inactive substance) and as effective as standard antidepressant medications for mild or moderate depression. It’s uncertain whether this is true for severe depression or for time periods longer than 12 weeks.
• Small numbers of studies suggest that St. John’s wort may be helpful for hot flashes associated with menopause and for somatic symptom disorder (a condition involving intense anxiety about physical symptoms).
• St. John’s wort has also been studied as a treatment for a variety of other conditions, including attention-deficit hyperactivity disorder (ADHD), irritable bowel syndrome, obsessive compulsive disorder, and premenstrual syndrome; as a possible aid to smoking cessation; and as an ingredient in topical preparations for wound healing. However, only a small amount of research has been done on the use of St. John’s wort for each of these purposes, and the evidence hasn’t clearly shown it to be helpful for any of them.

What Do We Know About Safety?

• For most adults who are not taking any kind of medicine, St. John’s wort appears to be safe when used for up to 12 weeks, and some studies indicate that it can be used safely for a year or more.
• If taken orally in large doses or applied to the skin, St. John’s wort might cause severe skin reactions after sun exposure. Other side effects can include diarrhea, dizziness, trouble sleeping, restlessness, and skin tingling.
• If you take any type of medicine, talk with your health care provider before using St. John’s wort or other herbal products; some herbs and medicines interact in harmful ways. 
  • For example, St. John’s wort can weaken the effects of many medicines, including crucially important medicines such as:
    • Some antidepressants, including amitriptyline and bupropion
    • Birth control pills
    • Cyclosporine, which prevents the body from rejecting transplanted organs
    • Some drugs used to prevent seizures, including phenytoin and carbamazepine
    • Some heart medications, including digoxin and ivabradine
    • Some HIV drugs, including indinavir and nevirapine
    • Some cancer medications, including irinotecan, imatinib, and docetaxel
    • Warfarin, an anticoagulant (blood thinner)
    • Certain statins, including simvastatin
• In addition, taking St. John’s wort with certain antidepressants or other drugs that affect serotonin (a substance produced by some nerve cells) may lead to increased serotonin-related side effects, which can be serious.
• It may be unsafe to use St. John’s wort during pregnancy because it may increase the risk of birth defects. Breastfeeding infants of mothers who take St. John’s wort can experience colic, drowsiness, and lethargy. 

Keep in Mind

• Depression can be a serious illness. If you or someone in your family may have depression, consult a health care provider.
• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions. Although it is important to tell your health care providers about any complementary health approaches you use, this is especially crucial for St. John’s wort because this herb interacts with so many medicines. Interactions with St. John’s wort can weaken the effects of life-saving medicines or cause dangerous side effects.
• Federal Regulation of Herbal Products
  • Depending on what’s in them, how they’re intended to be used, and how they’re administered (orally or topically), herbal products are regulated in a variety of ways. Many herbal products intended for oral use are marketed as dietary supplements. The regulatory paths for dietary supplements are different than those for drugs.
  • Unlike drugs, dietary supplements are not approved by the U.S. Food and Drug Administration (FDA) before they are sold to the public. When public health concerns arise about the safety of a dietary supplement or an ingredient including an herb, the FDA can take action to protect the public. Manufacturers and distributors of supplements are responsible for evaluating the safety and labeling of their products before marketing to ensure that they meet all regulatory requirements.

For More Information

• Using Dietary Supplements Wisely
• Know the Science: How Medications and Supplements Can Interact
• Know the Science: How To Make Sense of a Scientific Journal Article

Key References