St. John’s Wort 

This fact sheet provides basic information about the herb St. John’s wort— 

common names, uses, potential side effects, and resources for more 

information. St. John’s wort is a plant with yellow flowers whose medicinal uses 

were first recorded in ancient Greece. 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. 

Common Names—St. John’s wort, hypericum, Klamath weed, goat weed 

Latin Name—Hypericum perforatum 

What It Is Used For 

•	 St. John’s wort has been used for centuries to treat mental disorders and 

nerve pain. 

•	 St. John’s wort has also been used as a sedative and a treatment for malaria, 

as well as a balm for wounds, burns, and insect bites. 

•	 Today, St. John’s wort is used by some for depression, anxiety, and/or 

sleep disorders. 

How It Is Used 

The flowering tops of St. John’s wort are used to prepare teas and tablets 

containing concentrated extracts. 

What the Science Says 

•	 There is some scientific evidence that St. John’s wort is useful for treating 

mild to moderate depression. However, two large studies, one sponsored by 

NCCAM, showed that the herb was no more effective than placebo in 

treating major depression of moderate severity. 

•	 NCCAM is studying the use of St. John’s wort in a wider spectrum of mood 

disorders, including minor depression. 

Side Effects and Cautions 

•	 St. John’s wort may cause increased sensitivity to sunlight. Other side effects 

can include anxiety, dry mouth, dizziness, gastrointestinal symptoms, 

fatigue, headache, or sexual dysfunction. 

•	 Research shows that St. John’s wort interacts with some drugs. The herb affects 

the way the body processes or breaks down many drugs; in some cases, it may 

speed or slow a drug’s breakdown. Drugs that can be affected include: 

o	 Antidepressants 

o	 Birth control pills 

o	 Cyclosporine, which prevents the body from rejecting transplanted organs 
 

 

o	 Digoxin, which strengthens heart muscle contractions 

o	 Indinavir and possibly other drugs used to control HIV infection 

o	 Irinotecan and possibly other drugs used to treat cancer 

o	 Warfarin and related anticoagulants. 

•	 When combined with certain antidepressants, St. John’s wort may increase side effects 

such as nausea, anxiety, headache, and confusion. 

•	 St. John’s wort is not a proven therapy for depression. If depression is not adequately 

treated, it can become severe. Anyone who may have depression should see a health care 

provider. There are effective proven therapies available. 

•	 Tell your health care providers about any complementary and alternative practices you 

use. Give them a full picture of what you do to manage your health. This will help ensure 

coordinated and safe care. 

Sources 

National Center for Complementary and Alternative Medicine. St. John’s Wort and the Treatment of Depression. National 


Center for Complementary and Alternative Medicine Web site. Accessed at http://nccam.nih.gov/health/stjohnswort 


on June 29, 2007. 


St. John’s wort. Natural Medicines Comprehensive Database Web site. Accessed at http://www.naturaldatabase.com on 


June 29, 2007. 


St. John’s wort (Hypericum perforatum L.). Natural Standard Database Web site. Accessed at http://www.naturalstandard.com 


on June 28, 2007. 


St. John’s wort. In: Blumenthal M, Goldberg A, Brinckman J, eds. Herbal Medicine: Expanded Commission E Monographs.
 

Newton, MA: Lippincott Williams & Wilkins; 2000:359-366. 


De Smet PA. Herbal remedies. New England Journal of Medicine. 2002;347(25):2046-2056. 


Hypericum Depression Trial Study Group. Effect of Hypericum perforatum (St. John’s wort) in major depressive disorder: 


a randomized controlled trial. Journal of the American Medical Association. 2002;287(14):1807-1814. 


For More Information 

Visit the NCCAM Web site at nccam.nih.gov and view: 

•	 What’s in the Bottle? An Introduction to Dietary Supplements at nccam.nih.gov/health/bottle/ 

•	 Herbal Supplements: Consider Safety, Too at nccam.nih.gov/health/supplement-safety/ 

NCCAM Clearinghouse 

Toll-free in the U.S.: 1-888-644-6226 

TTY (for deaf and hard-of-hearing callers): 1-866-464-3615 

E-mail: info@nccam.nih.gov 

CAM on PubMed 

Web site: nccam.nih.gov/camonpubmed/ 

NIH Office of Dietary Supplements 

Web site: www.ods.od.nih.gov 

NIH National Library of Medicine’s MedlinePlus 

St. John’s Wort Listing: www.nlm.nih.gov/medlineplus/druginfo/natural/patient-stjohnswort.html 

This publication is not copyrighted and is in the public domain. Duplication is encouraged. 

NCCAM has provided this material for your information. It is not intended to substitute for the medical 

expertise and advice of your primary health care provider. We encourage you to discuss any decisions 

about treatment or care with your health care provider. The mention of any product, service, or therapy 

is not an endorsement by NCCAM. 

National Institutes of Health 

♦♦♦

U.S. Department of Health and Human Services 

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Created July 2005 

Updated March 2008 

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