St. John's Wort

Dear Alice,

What is the most recent information on the beneficial effects of St. John's wort and possible side effects? What is the recommended dose?


Dear M, 

What’s the word on St. John’s wort? Named because it usually blooms around John the Baptist's birthday, the plant is also known by its botanical name, Hypericum perforatum. This supplement is derived from a yellow flowering plant native to Europe, parts of Asia and Africa, and the western United States. It has been used—with mixed results—as an herbal remedy for a wide range of physical and emotional ailments. The active ingredients in St. John's wort include hypericin and pseudohypericin, but it is unknown whether these components cause the healing properties of St. John's wort. More research is needed to better understand how this herb works and its potential health benefits and side effects. The usual dose for adults is 300 milligrams (mg) with 0.3 percent hypericin extract, taken three times a day with food—effects are typically felt within three to six weeks of taking the supplement. How much of the supplement to take and the number of times you'll need to take it daily will vary depending on the condition you wish to treat. 

St. John’s wort is thought to treat a number of health concerns including mild to moderate depression, menopausal symptoms, somatization disorder (when mental experiences are converted into physical symptoms in the body), wound and minor burn healing, seasonal affective disorder (SAD), eczema, hemorrhoids, obsessive-compulsive disorder, and even social phobias. Research suggests that St. John's wort raises levels of serotonin, norepinephrine, and dopamine (different neurotransmitters that help boost morale and mood). 

Although the evidence is mixed, there are a number of studies that suggest St. John’s wort can be effective in treating mild to moderate depression without the side effects common to traditional anti-depressant medications. That being said, it’s not recommended for treating severe depression. Unlike prescription anti-depressants, which can cause side effects such as lowered sex drive and delayed ejaculation or orgasm, the same sexual side effects haven’t been associated with the use of St. John's wort. 

However, this doesn’t mean that the supplement is free from potential adverse side effects, some of which include: 

  • Fatigue 
  • Dry mouth 
  • Dizziness 
  • Vivid dreams 
  • Headache 
  • Skin rash 
  • Gastrointestinal discomfort, such as diarrhea 
  • Allergic reactions 
  • Irritability 
  • Restlessness 
  • Increased sensitivity to sunlight 
  • Confusion 
  • Anxiety 

If you experience side-effects or choose to stop taking St. John's wort for any reason, quitting cold turkey isn’t recommended. It’s best to speak with your health care provider to help you decide how to stop, but generally speaking it's best to gradually lower your dose before stopping. 

Due to the lack of scientific evidence, it’s hard to know how taking St. John’s wort may affect different individuals. You may want to be especially wary of taking this supplement if you: 

  • Are taking prescription medications. Anti-depressant medications, monoamine oxidase inhibitors (MAOIs), and HIV/AIDS medications combined with St. John’s wort can lead to possibly dangerous interactions. Combined with anti-depressants, St. John's wort could make life-threateningly high levels of serotonin. Additionally, St. John’s wort can affect how the body metabolizes medicine, which may make certain medications less effective. But if you’re using any other medications, prescription or otherwise, it’s best to let your health care provider know before taking St. John’s wort. 
  • Are pregnant or breastfeeding. Limited research has been done on individuals who are pregnant or breastfeeding. Until more is known, those who are pregnant or breastfeeding are advised not to take St. John's wort. 
  • Do you have or are you at risk of high blood pressure. Components of St. John's wort may raise blood pressure, possibly resulting in a stroke. It's critical that those who are already at risk of high blood pressure be especially cautious. 
  • Have certain mental health conditions. People with ADD/ADHD, bipolar disorder, or schizophrenia can experience worse symptoms as a result of St. John's wort, but more research is needed to understand why this happens. 

As a rule, it’s helpful to remember that "natural" doesn’t necessarily mean safe. Since St. John's wort is an herbal supplement and not regulated by the U.S. Food and Drug Administration (FDA), the quality of the supplement may vary. For more information on the topic, consider visiting the National Center for Complementary and Integrative Health website. Before trying St. John's wort, or any other natural supplement, it’s recommended that you talk with your health care provider. Doing so may help you gather information to help you decide wort the best course of action is for you. 

Last updated Apr 28, 2023
Originally published Aug 28, 1998

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