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St. John's wort (Hypericum perforatum) is a plant historically used in traditional European medicine, and is most known today as an herbal supplement for treating mild to moderate depression. However, it has numerous dangerous interactions with medications and should be used with caution and under medical supervision.
Uses and effectiveness
Likely effective:
Mild to moderate depression: Numerous studies indicate St. John's wort is effective for treating mild to moderate depression, performing as well as some prescription antidepressants with fewer side effects. However, results are inconsistent for severe depression.
Somatic symptom disorder: Some research shows that St. John's wort may help alleviate this disorder, which causes severe anxiety over physical symptoms.
Menopause symptoms: Some studies suggest it can reduce hot flashes and other symptoms of menopause.
Possibly effective (more research needed):
Wound healing: Historically used for minor wounds, burns, and bruises, St. John's wort can be applied topically to the skin as an oil, cream, or salve.
Obsessive-compulsive disorder (OCD): Preliminary evidence suggests it may help with OCD symptoms, but more research is needed.
Seasonal affective disorder (SAD): Some evidence suggests it may help with SAD, the "winter blues".
Anxiety and insomnia: Used as a mild tranquilizer to calm mood and help with sleep issues.
Premenstrual syndrome (PMS): May help alleviate PMS symptoms like mood swings and fatigue.
Psoriasis: Topical use has been studied for mild to moderate plaque-type psoriasis.
Side effects
While often considered generally well-tolerated, St. John's wort can cause side effects. Common side effects include:
Headache
Upset stomach, diarrhea, or constipation
Dizziness or fatigue
Dry mouth
Restlessness and trouble sleeping
Increased sensitivity to sunlight (photosensitivity), especially in fair-skinned individuals
Dangerous drug interactions
St. John's wort is known to have dangerous, and sometimes life-threatening, interactions with many medications. It can speed up drug metabolism in the body, reducing the effectiveness of other medications. A partial list of interacting medications includes:
Antidepressants and other serotonergic drugs: Combining St. John's wort with other antidepressants, including SSRIs, can lead to a dangerous buildup of serotonin, known as serotonin syndrome.
Birth control pills: St. John's wort can cause breakthrough bleeding and reduce the effectiveness of oral contraceptives, potentially leading to unintended pregnancy.
Blood thinners: It can decrease the effect of blood thinners like warfarin, increasing the risk of blood clots.
Immunosuppressants: It can reduce the blood levels of medications like cyclosporine and tacrolimus, which can lead to organ rejection in transplant patients.
HIV/AIDS medications: It can significantly reduce the effectiveness of many anti-HIV drugs.
Cancer chemotherapy drugs: St. John's wort can reduce the effectiveness of certain cancer treatments.
Heart medications: It can interact with medicines like digoxin.
Cholesterol-lowering medications: It can reduce the effectiveness of some statins.
Important safety warnings
Talk to your doctor first: Before taking St. John's wort, consult a healthcare provider, especially if you take any prescription medication. Inform all healthcare providers and pharmacists of any herbal supplements you are taking.
Not FDA regulated: In the U.S., St. John's wort is sold as a dietary supplement and is not approved by the FDA. Products can vary in purity and strength.
Not for everyone: Do not use St. John's wort if you are pregnant, breastfeeding, have severe depression, or have bipolar disorder, as it may trigger mania.
Avoid before surgery: Stop taking St. John's wort at least 5 to 10 days before any scheduled surgery.