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St John’s Wort

Hypericum perforatum

What is St John’s Wort?

Other Names: Johnswort, Touch-and-heal, Goat weed, Hardhay.

St. John's wort is very recognisable as it is a plant with yellow, star-shaped flowers.

What are the potential benefits of St John’s Wort?

It is said in the Ancient Greek civilisation, this herb was recommended its use for a variety of nervous and mood disorders. It was also used as traditional folk medicine for disease of the kidney, infections, wound healing and again, to alleviate nervous system related disorders. More recent information suggests other chemicals like hyperforin may play a role in its therapeutic applications. These chemicals act on messengers in the nervous system that regulate mood.


A placebo-controlled clinical trial was conducted including 40 patients with major depressive disorder .The results of the study suggested that St. John's Wort is effective when taken with tricyclic antidepressants as it had significant effect on mild to moderate depression improvement compared to the group on antidepressants alone. The group provided St. John's Wort also had improved sleep compared to the group who were not given the herb [i]. However, it is not advisable to mix these medications with St. John’s Wort due to the risk of side effects (please see interaction section). It is advisable to check the instructions on the particular brand of supplement taken, or follow guidance of a qualified herbal or natural health practitioner.

Preliminary research suggests that St. John's Wort also lowers levels of the stress hormone cortisol and enhances the activity of gamma-aminobutyric acid (GABA) [ii]. It is also thought the antidepressant action of St John’s Wort can be due to its action as a mild monoamine oxidase (MAO) inhibitor. MAO is an enzyme which breaks down two brain chemicals; serotonin and norepinephrine. By inhibiting MAO and increasing norepinephrine, St. John's Wort may exert a mild anti-depressive action [iii]. The effects relating to antidepressant or mood elevating effects of St. John's Wort were originally thought to be due solely to hypericin [iv]. However, alike most herbal products, many other present constituents such as xanthones and flavonoids may attribute to the therapeutic actions of the herb [v].

SAD (Seasonal Affective Disorder)

Seasonal depression also known as Seasonal Affective Disorder or SAD, occurs in the winter due to lack of sunlight. Early studies show that St. John's wort might help improve symptoms of nervousness, decreased libido and sleep problems in people with this condition [vi] [vii].

Another effective treatment for SAD is to spend time every day in full spectrum light, with use of light-boxes seen to particular efficacious in SAD [viii]. Also, using this herb in combination with phototherapy may also work to increase the effect. Whilst one of the side effects of this plant can be increased photosensitivity, light-box therapy can be safely combined with St John's Wort as light-boxes do not produce the type of ultraviolet light which affects the skin [ix].

OCD (Obsessive Compulsive Disorder)

Research has found that Selective Serotonin Re-uptake Inhibitors (SSRI’s) can be effective against OCD. This discovery lead researchers to speculate about the potential of St John’s Wort as a natural alternative. A small-scale clinical study on 13 OCD patients was completed, participants received St John’s Wort, twice daily, for 12 weeks. At the end of the study, doctors rated 42% of the participants as “much” or “very much improved”. It was concluded that the positive effects seen in the study warrant further investigation for use in this condition [x].

Pre-Menstrual Syndrome (PMS)

The results of a randomised, double blind, placebo controlled trial found that St John’s Wort was statistically more beneficial than the placebo against symptoms including food cravings, swelling (water retention), poor co-ordination, insomnia, confusion, headaches, crying and fatigue [xi].

Menopausal hot flashes

Studies have found combinations of St. John's wort used together with black cohosh are also beneficial for menopausal hot flashes [xii].

Healing wounds

Evidence suggests St. John’s wort may be indicated as an effective treatment in promoting the healing of wounds, bruises, burns, and pressure sores, such as bed sores [xiii].


Early research shows that taking St. John's wort product three times daily improves migraine pain, however it did not reduce migraine frequency[xiv].


A report of 3 males aged 14-16 with ADHD showed that taking St. John's wort daily for 4 weeks might improve attention and activity. However, other studies to the contrary allow the research in this area to remain inconclusive as of yet [xv] [xvi].


Please note: St John’s Wort has many interactions with medications and other herbal remedies due to its effect on a liver enzyme family known as cytochrome P450 [xvii].

Avoid use alongside the contraceptive pill, anti-epilepsy treatments, 5-htp, and a number of other medications including anti-depressants. St John's wort should not be combined with a MAO inhibitor antidepressants. This combination can produce a dangerous rise in blood pressure along with severe anxiety, fever, muscle tension, and confusion. After stopping a MAO inhibitor, it is advisable to leave a break of at least four weeks before taking other antidepressants, including Hypericum. If taking any medication it is strongly advised to consult your prescribing doctor before starting St John's Wort.


Do not use St. John's Wort during pregnancy or lactation [xviii].

This herb should not be taken together with foods that contain tyramine i.e. cheese, red wine, preserved meats and yeast extracts. This is due to a MAO inhibition effect.

Those with fair skin should avoid exposure to strong sunlight and other sources of ultraviolet light as St. John's Wort may make the skin more light sensitive.


As well as having been used safely for centuries of folk medicine, the current clinical safety data suggests St John’s Wort id comparable to and possibly safer than conventional antidepressant medication when used for mild depression [xix]. There were none of the effects seen in conventional drug use such as: sedative effects, digestive disturbances and sexual dysfunction, often found in patients treated with tricyclic antidepressants or selective serotonin re-uptake inhibitors [xx].

Recommended For

Stress , Anxiety , Depression , Menopause

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