St John's wort

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St. John's Wort
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Scientific classification
Species:H. perforatum
Binomial name
Hypericum perforatum

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


The plant

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 common name comes from the fact that it traditionally flowers by and is harvested on St John's day, 24 June. The genus name "hypericum" is derived from the Greek words hyper (above) and eikon (picture) in reference to the traditional use of the plant to ward off evil, by hanging plants over a picture in the house during St John's day. The species name "perforatum" refers to the small windows in the leaves, which can be seen when they are held against the light.

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.

Uses of the herb

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. The aerial parts of the plant can be 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.

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.

St. John's wort is today most widely known as a possible treatment for depression. 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 tablet or capsule form. It is also available in teabags and tinctures to be diluted in water.

Clinical evidence

Plantlets of St. John's wort
Plantlets of St. John's wort

Clinical studies of St John's wort preparations have mainly focused on the efficacy of the herb in clinical depression. There have been mixed results over the efficacy of St. John's wort in clinical depression. Some studies have found it to be effective in the treatment of mild to moderate depression, with fewer side effects than many conventional antidepressants, while others show no benefit over placebo.

Evidence for efficacy

An early meta-study indicated that extracts of hypericum may be more effective than placebo for the treatment of mild to moderately severe depressive disorders. (Linde et al., 1996) This study, which covered the results from 23 smaller, earlier studies, is perhaps the most often cited by manufacturers and other supporters of St. John's wort.

This meta-analysis study was later updated to include further studies, for a total of 27, to form a Cochrane Review. The updated review found that Hypericum preparations were significantly superior to placebo (rate ratio 2.47; 95% confidence interval 1.69 to 3.61) and similarly effective as standard antidepressants (single preparations 1.01; 0.87 to 1.16, combinations 1.52; 0.78 to 2.94). (Linde & Mulrow, 2003)

Another meta-analysis, with stricter inclusion criteria, found that Hypericum was more effective than placebo; and as effective as tricyclic antidepressants, with fewer adverse drug reactions. (Kim et al., 1999) This meta-analysis showed that the response rate for St. Johns wort was significantly greater than that for placebo (73.2 versus 37.9%, respectively, relative risk 1.48 and 95% CI 1.031.92) and similar to that observed with tricyclic antidepressants (64 versus 66.4% for St. Johns wort and tricyclic antidepressants, respectively, relative risk 1.11 and 95% CI 0.921.29).

Other more recent trials have also showed greater efficacy than placebo; and comparable efficacy to standard antidepressants with a superior adverse effect profile. (Laakman et al., 1998; Harrer et al., 1999; Philipp et al., 1999)

Evidence against efficacy

A major study funded by the NIH in the United States, found St John's wort to be ineffective in treating major depression of moderate severity. (Hypericum Depression Trial Study Group, 2002) This study involved 340 patients, diagnosed with Major Depressive Disorder based on DSM-IV criteria and assessed using Hamilton Depression Scale (HAM-D) and Clinical Global Impression (CGI) scores. The trial was a multi-centre randomised double-blind placebo-controlled trial, comparing one preparation of St John's wort to sertraline and placebo. St. John's wort proved no more effective than placebo in alleviating moderately severe major depression. It should be noted that sertraline was also no better than placebo in this study, based on the primary outcome measure (HAM-D). Further studies on the herb's efficacy in alleviating mild depression are planned by the NIH.

As with most studies into complementary therapies, many are hampered by poor methodologies and study designs; preventing definitive evidence from emerging. The author of one of the trials with positive results stated that, "Further studies comparing hypericum with standard antidepressants in well defined groups of patients over longer observations periods, investigating long term side effects, and comparing different extracts and doses are needed." (Linde & Mulrow, 2003)


Although the exact mechanism by which St. John's wort works is unclear, it is believed to involve inhibition of Serotonin (5-HT) reuptake, much like the conventional SSRI antidepressants. It should be noted that the exact mechanism of even the conventional antidepressants is subject to much conjecture.

The major active constituents in St John's wort are thought to be hyperforin and hypericin, although other biologically active constituents present, e.g. flavonoids and tannins, may also be involved. (Nahrstedt & Butterweck, 1997)

Hyperforin is believed to be the major constituent responsible for antidepressant activity, and has been shown to inhibit the uptake of 5-HT, dopamine, noradrenaline, GABA and glutamate. (Chatterjee et al., 1998a) Discrepancies in the dose-response relationship imply that constituents other than hyperforin are likely to also be involved. (Chatterjee et al., 1998b)


The dosage of St John's wort preparations vary greatly between formulations, due to variability in the plant source and preparation processes. The doses of St. Johns wort extract used in clinical trials generally range from 350 to 1800 mg daily (equivalent to 0.4 to 2.7 mg hypericin depending on the preparation). (Linde & Mulrow, 2003)

The recommended dosage for various forms of St John's wort as recommended by the British Herbal Medicine Association Scientific Committee (1983) are as follows:

  • dried herb: 2-4 g or by infusion three times daily
  • liquid extract 2-4 mL (1:1 in 25% alcohol) three times daily
  • tincture 2-4mL (1:10 in 45% alcohol) three times daily

In markets where standardised 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. Even where extracts are standardised it is debatable whether using hypericin as the standard is useful, since hyperforin is believed to be the main active constituent.

As with other antidepressants, Hypericum should be taken for at least four weeks before its effectiveness can be properly assessed.

Adverse effects

St John's wort is generally well tolerated, with an adverse effect profile similar to placebo. (Ernst et al., 1998). The most common adverse effects reported are gastrointestinal symptoms, dizziness, confusion and tiredness/sedation. (Barnes et al., 2002)

St John's wort is also known to cause photosensitivity, which can lead to sunburns in situations that would not normally cause them, but the incidence is reported to be extremely rare. (Ernst et al., 1998).

Drug interactions

St John's wort has been shown to cause multiple drug interactions through induction of the cytochrome P450 enzyme CYP3A4. The principal constituent thought to be responsible is hyperforin which, unfortunately, is also believed to be the active constituent.

St John's wort decreases the levels of certain medications in the body thereby decreasing their efficacy. Such medications may include other antidepressants (SSRIs and TCAs), contraceptives, cholesterol-lowering medications, etc. Patients on any medications (including over-the-counter) are advised to consult their pharmacist or physician prior to taking any product containing St John's Wort.


  • Barnes J, Anderson LA, Phillipson JD (2002). Herbal Medicines: A guide for healthcare professionals (2 ed.) London: Pharmaceutical Press. ISBN 0-8536947-4-5
  • British Herbal Medicine Association Scientific Committee (1983). British Herbal Pharmacopoeia. West Yorkshire: British Herbal Medicine Association. ISBN 0-9030320-7-4
  • Chatterjee SS, Bhattacharya SK, Wonnemann M, Singer A, Muller WE (1998a). Hyperforin as a possible antidepressant component of hypericum extracts. Life Sci 63 (6), 499-510.
  • Chatterjee SS, Noldner M, Koch E, Erdelmeier C (1998b). Antidepressant activity of hypericum perforatum and hyperforin: the neglected possibility. Pharmacopsychiatry 31 (Suppl 1), 7-15.
  • Ernst E, Rand JI, Barnes J, Stevinson C (1998). Adverse effects profile of the herbal antidepressant St. John's wort (Hypericum perforatum L.). Eur J Clin Pharmacol 54 (8), 589-94.
  • Harrer G, Schmidt U, Kuhn U, Biller A (1999). Comparison of equivalence between the St. John's wort extract LoHyp-57 and fluoxetine. Arzneimittelforschung 49 (4), 289-96.
  • Hypericum Depression Trial Study Group (2002). Effect of Hypericum perforatum (St John's Wort) in Major Depressive Disorder. ( JAMA 287 (14), 1807-1814.
  • Kim HL, Streltzer J, Goebert D (1999). St. John's Wort for Depression: A Meta-Analysis of Well-Defined Clinical Trials. J Ment Nerv Dis 187 (9), 532-538.
  • Laakmann G, Schule C, Baghai T, Kieser M (1998). St. John's wort in mild to moderate depression: the relevance of hyperforin for the clinical efficacy. Pharmacopsychiatry 31 (Suppl 1), 54-9.
  • Linde K, Ramirez G, Mulrow CD, Pauls A, Weidenhammer W, Melchart D (1996). St Johns wort for depression an overview and meta-analysis of randomised clinical trials. ( Br Med J 313, 253258.
  • Linde K, Mulrow CD (2003). St John's wort for depression (Cochrane Review). In: The Cochrane Library, Issue 3, 2004. Chichester, UK: John Wiley & Sons, Ltd.
  • Nahrstedt A, Butterweck V (1997). Biologically active and other chemical constituents of the herb of Hypericum perforatum L. Pharmacopsychiatry 30 (Suppl 2), 129-34.
  • Philipp M, Kohnen R, Hiller KO (1999). Hypericum extract versus imipramine or placebo in patients with moderate depression: randomised multicentre study of treatment for eight weeks. Br Med J 319 (7224), 1534-8.

External links

eo:Hiperiko punktita fi:Mkikuisma ja:セント・ジョーンズ・ワート nl:Sint Janskruid pl:Dziurawiec fr:Millepertuis perfor


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