St. John's Wort (Hypericum perforatum) is a wild-growing plant that has been used as a sedative and treatment for malaria, wounds, burns, and insect bites since the time of Hippocrates. Today, St. John's Wort is used by some people to treat mild to moderate depression, anxiety, or sleep disorders.
The active ingredients that produce the herb's effects probably include the compounds hypericin and hyperforin. Preliminary studies suggest that St. John's Wort might work by preventing nerve cells in the brain from reabsorbing the chemical messenger serotonin.
In 1996, the British Medical Journal Review, Ed. 23, clinical studies suggested that St. John's Wort might be useful in cases of mild depression; however, none of these studies lasted more than six weeks, and the diagnosis was not always well established. A recent randomized, double-blind trial funded by the National Institutes of Health found that an extract of St. John's Wort was no more effective for treating major depression of moderate severity than placebo. (JAMA 2002; 287:1807).
Side effects from St. John's Wort include dry mouth, dizziness, gastrointestinal symptoms, increased sensitivity to sunlight, and fatigue. St. John's Wort interacts with antidepressant drugs, dextromethorphan, tetracycline, Indinavir, digoxin and warfarin. Women who are pregnant or are breastfeeding should not use it.