St. John’s Wort

© Steven Foster

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

common names, what the science says, potential side effects and 

cautions, and resources for more information.

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

goatweed.

Latin Name—Hypericum perforatum

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. Historically, St. John’s wort has been 

used for centuries to treat mental disorders and nerve pain. St. John’s wort 

has also been used for malaria, as a sedative, and as a balm for wounds, 

burns, and insect bites. Today, St. John’s wort is used as a folk or 

traditional remedy for depression, anxiety, and/or sleep disorders.

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

and capsules containing concentrated extracts. Liquid extracts and 

topical preparations are also used.

What the Science Says 

Although some studies of St. John’s wort have reported benefits for 

depression, others have not. For example, a large study sponsored by 

NCCAM found that the herb was no more effective than placebo in 

treating major depression of moderate severity, and a study co-funded 

by NCCAM and the National Institute of Mental Health found that 

neither St. John’s wort nor a standard antidepressant medication 

relieved symptoms of minor depression better than a placebo. 

Side Effects and Cautions

• Research has shown that St. John’s wort interacts with many 

medications in ways that can interfere with their intended effects. 

Examples of medications that can be affected include:

o Antidepressants

o Birth control pills

o Cyclosporine, which prevents the body from rejecting 

transplanted organs
o Digoxin, a heart medication

o Indinavir and possibly other drugs used to control HIV infection

o Irinotecan and possibly other drugs used to treat cancer

o Seizure-control drugs, such as phenytoin and phenobarbital

o Warfarin and related anticoagulants.

• 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.

• Taking St. John’s wort with certain antidepressants may lead to increased serotonin-related side effects, 

which may be potentially serious.

• 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 all your health care providers about any complementary health practices you use. Give them a full 

picture of what you do to manage your health. This will help ensure coordinated and safe care. For tips 

about talking with your health care providers about complementary and alternative medicine, see 

NCCAM’s Time to Talk campaign at nccam.nih.gov/timetotalk/. 

Sources

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.

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

Alternative Medicine Web site. Accessed at nccam.nih.gov/health/stjohnswort/sjw-and-depression.htm on June 3, 2010.

Rapaport MH, Nierenberg AA, Howland R, et al. The treatment of minor depression with St. John’s wort or citalopram: Failure to show 

benefit over placebo. Journal of Psychiatric Research. 2011;45(7):931-941.

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.

St. John’s wort. Natural Medicines Comprehensive Database Web site. Accessed at www.naturaldatabase.com on February 15, 2010.

St. John’s wort (Hypericum perforatum L.). Natural Standard Database Web site. Accessed at www.naturalstandard.com on February 15, 2010.

For More Information

Visit the NCCAM Web site at nccam.nih.gov and view Using Dietary Supplements Wisely (nccam.nih.gov/health/supplements/wiseuse.htm).

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

PubMed®

Web site: www.ncbi.nlm.nih.gov/sites/entrez

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/329.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

D269

Created July 2005

Updated April 2012