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St. John's Wort
What is it? Overview Usage Side Effects and Warnings

What is St. John's Wort?

St. John's wort is a common perennial herb of many branches and bright yellow flowers that grows wild in much of the world. Its name derives from the herb's tendency to flower around the feast of St. John. (A wort simply means plant in Old English.) The species name perforatumderives from the watermarking of translucent dots that can be seen when the leaf is held up to the sun.

St. John's wort has a long history of use in treating emotional disorders. During the Middle Ages, St. John's wort was popular for "casting out demons." In the 1800s, the herb was classified as a nervine, or a treatment for "nervous disorders." When pharmaceutical antidepressants were invented, German researchers began to look for similar properties in St. John's wort.

Today, St. John's wort is a widely used treatment for depression in Germany, other parts of Europe, and the United States. The evidence-base for its use approaches that of many modern prescription drugs at the time of their first approval.

Most studies of St. John's wort have evaluated individuals with major depression of mild to moderate intensity. This contradictory-sounding language indicates that the level of depression is more severe than simply feeling "blue." However, it is not as severe as the most severe forms of depression. Typical symptoms include depressed mood, lack of energy, sleep problems, anxiety, appetite disturbance, difficulty concentrating, and poor stress tolerance. Irritability can also be a sign of depression.

Taken as a whole, research suggests that St. John's...

Safety Issues

St. John's wort taken alone usually does not cause immediate side effects. In a study designed to look for side effects, 3,250 people took St. John's wort for 4 weeks. 1 Overall, about 2.4% reported problems. The most common complaints were mild stomach discomfort (0.6%), allergic reactions—primarily rash—(0.5%), tiredness (0.4%), and restlessness (0.3%). Another study followed 313 individuals treated with St. John's wort for 1 year. 2 The results showed a similarly low incidence of adverse effects.

In the extensive German experience with St. John's wort as a treatment for depression, there have been no published reports of serious adverse consequences from taking the herb alone. 3 Animal studies involving enormous doses of St. John's wort extracts for 26 weeks...