St John's wort
| St. John's wort | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Scientific classification | ||||||||||||||
| ||||||||||||||
| Binomial name | ||||||||||||||
| Hypericum perforatum L | ||||||||||||||
St John's wort used alone refers to the species Hypericum perforatum, also known as Klamath weed or Goat weed, but is used with qualifiers to refer to any species of the genus Hypericum. H. perforatum is sometimes called Common St. John's wort to distinguish it. The species of Hypericum have been placed by some in the family Hypericaceae, but more recently have been included in the Clusiaceae
Hypericum perforatum is a yellow-flowering, rhizomatous, perennial herb indigenous to Europe, which has been introduced to the Americas and grows wild in many meadows. The name comes from the fact that it traditionally flowers by and is harvested on St John's day; all above-ground parts are cut and dried for later use in the form of herbal tea, which has long been enjoyed both for its pleasant (though somewhat bitter) taste and for its medicinal properties.
The name perforatum refers to the small windows in the leaves, which can be seen when they are held against the light.
In modern medicine, standardized Hypericum extract (obtained from H. perforatum) is commonly used as a treatment for depression and anxiety disorders. In homeopathy, Hypericum is used in the treatment of numerous medical problems, yet the rate of success has not been adequately documented. Historically, the flowers and stems of St John's wort have also been used to produce red and yellow dye.
Although Hypericum perforatum is grown commercially in some regions, it is listed as a noxious weed in over twenty countries. Ingestion by livestock can cause photosensitization, central nervous system depression, spontaneous abortion, and can lead to death. Effective herbicides for control of Hypericum include 2,4-D, picloram, and glyphosate. In western North America three beetles Chrysolina quadrigemina, Chrysolina hyperici and Agrilus hyperici have been introduced as biocontrol agents.
The first recorded use of Hypericum for medicinal purposes dates back to ancient Greece, and it has been used ever since. The herb was also used by Native Americans internally as an abortifacient and externally as an anti-inflammatory, astringent, and antiseptic.
St. John's wort is today most famously known as a possible treatment for depression. It has been found to be of no noticeable effect in the treatment of more serious forms of depression as reported in a major NIH-funded study completed in 2002 [1], which concluded that "St. John's wort is not effective in treating major depression of moderate severity." A companion study on the wort's efficacy in alleviating mild depression is planned by the NIH. Another article in the Journal of the American Medical Association [1] also reported that, in a separate tudy of 340 patients diagnosed with severe depression, St. John's wort proved no more effective than placebo in alleviating "moderately severe" depression symptoms. Some US researchers have expressed skepticism about the earlier German studies [1], which were carried out by primary care physicians.
There is disagreement about the effects of St. John's wort on mild depression. Some clinical studies have found it to be effective in the treatment of mild to moderate depression, with fewer side effects than many conventional antidepressant medications. In some countries such as Germany, Hypericum is prescribed for mild depression, far more commonly than conventional antidepressant medication. Standardized extracts can be bought today as an over-the-counter remedy, usually in pill or capsule form. It is also widely sold in teabags. A early "meta-study", encompassing the results of a number of smaller studies and printed in the British Medical Journal in 1996 [1] did not unequivocally endorse the use of St. John's wort as a treatment for any kind of depression, but did note that "there is evidence that extracts of hypericum are more effective than placebo for the treatment of mild to moderately severe depressive disorders." This study, which covered the results from 23 smaller, earlier studies, is perhaps the most often mentioned by manufacturers and other supporters of St. John's wort. It is important to note that this BMJ article, in finding that St. John's wort is effective for both mild and "moderately severe" depression symptoms, is in conflict with the two more recent 2002 studies reported above.
Although the exact mechanism by which St. John's wort works is unclear, it is believed to involve slowing the disposal of serotonin, thus boosting serotonin levels. Common side effects are extraordinarily vivid dreams (especially if taken just before bedtime), somewhat increased appetite, and a heightened production of urine by the kidneys, thus requiring the patient to increase fluid intake to avoid dehydration.
The usual dosage is 900 mg of Hypericum extract per day, usually made up of three 300 mg capsules or tablets taken at different times of the day. The dosage might need to be varied according to the patient's body weight. Advocates recommend that, as with other antidepressants, Hypericum be taken for at least four weeks before judging its effectiveness.
In markets where standardized extracts are not available, the potency of samples can vary widely. Some brands of over-the-counter St. John's wort can be much more potent than others. The same can even be true of two dosage units from different batches of the same brand.
Casual use of Hypericum extracts in patients on other medication is not recommended as it can cause sometimes serious drug interactions, including preventing other antidepressants from functioning. It also is known to cause photosensitivity, i.e. increased sensitivity to light, which can lead to sunburns in situations that would not normally cause them.
Medicinal properties
External links