How does St. John's wort work?

St. John's wort is an herbal remedy that some people believe can be used to treat depression. They are turning to St. John's wort because many of the psychotropic drugs used to treat depression have some severe side effects, and they hope that a medicine derived from a plant will cause fewer problems.

About 17 million Americans suffer from depression. Depression can be treated in a number of ways, most commonly by the use of anti-depressant drugs, such as Prozac, Paxil, Elavil and Nardil. The possible side effects of these drugs include sleeplessness, headaches, gastrointestinal disturbances and changes in sexual desire or activity. A 1994 study, reported in the British Medical Journal, indicated that St. John's wort was about as effective as standard anti-depressants -- better than sugar pill placebos in treating mild to moderate depression.


St. John's wort (hypericum perforatum) is a perennial shrubby plant with golden flowers. The active therapeutic ingredients in St. John's wort are hypericin, pseudohypericin and xanthones, although other components may support the action of these compounds. St. John's wort extract preparations are standardized to 0.3 percent hypericin. The typical adult dosage is 300 milligrams taken three times a day, and that means that a person taking St. John's wort gets 2.7 milligrams of hypericin a day.

It is not clear how St. John's wort works to treat depression. Most likely, hypericin helps to elevate the biochemicals in the brain that affect mood, namely dopamine and serotonin, and to reduce andrenal activity, which is increased in depression. St. John's wort has side effects, too. The most common are light-sensitivity, dry mouth, stomach irritations, dizziness and tiredness.

St. John's wort may help with the treatment of some retroviruses, such as herpes, HIV and friend leukemia virus, and could help in treating some cancers; however, the evidence is not nearly as conclusive for the treatment of these conditions as it is for depression.

Clinical trial studies are under way in the United States to determine just how effective St. John's wort is for treating depression. Because St. John's wort is marketed as a dietary supplement, it is not regulated by the U.S. Food and Drug Administration. Any use of this substance should be done under a doctor's supervision. Check out How St. John's Wort Works for a longer discussion of this topic.

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