St. John's Wort

On this page:

• What the Science Says
• Side Effects and Cautions
• Sources
• For More Information

Introduction

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.

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.

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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.

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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:
  • Antidepressants
  • Birth control pills
  • Cyclosporine, which prevents the body from rejecting transplanted organs
  • Digoxin, a heart medication
  • Indinavir and possibly other drugs used to control HIV infection
  • Irinotecan and possibly other drugs used to treat cancer
  • Seizure-control drugs, such as phenytoin and phenobarbital
  • 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.

Search the scientific literature for potential herb-drug interactions

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