St John's wort
Technically, St John's wort is classed as a noxious weed in some regions of Australia, but the medical world is becoming increasingly interested in the plant that has been called a ‘humble little roadside weed’.
In September 2000, the British Medical Journal published a study undertaken by German researchers who compared St John’s wort with the antidepressant imipramine as a treatment for mild to moderate depression, and concluded that the herbal treatment was ‘therapeutically equivalent’ to imipramine.
It has been noted, though, in some of the correspondence regarding the trial, that imipramine is an older antidepressant and may have more side effects than some modern antidepressants in conventional use.
The issue has never been more relevant — every year nearly 800,000 Australian adults experience a depressive illness, and the World Health Organization predicts that depression will be the world’s second largest health problem behind heart disease by 2020.
A review in the Journal of Clinical Psychiatry, published in November 2000, warned of the potentially dangerous effects of over-the-counter preparations sold as antidepressants. The review concluded that while some over-the-counter remedies for depression may be safe for some people, ‘more research is required before these agents can be recommended for routine use’.
What is St John’s wort?
St John’s wort (Hypericum perforatum) is a perennial herb native to Europe, North Africa and western Asia. It has been introduced to Africa, Asia, Australia and the Americas and is found growing prolifically in dry ground such as neglected fields, dry pastures, rangelands and along the side of roads.
St John’s wort is so named because the plant opens its yellow flowers in the northern hemisphere around the feast day of St John the Baptist in late June. Wort is an old English word for plant.
St John’s wort has been used to treat nervous conditions since ancient Greek times and was also used for its sedative and antimalarial properties. In the 19th and 20th centuries, St John’s wort was used to treat hysteria and nervous diseases with depression. It has also been used to treat wounds, bruises and sprains.
Today, St John’s wort is officially listed in the national pharmacopoeias of Czechoslovakia, France, Poland, Romania and Russia.
What are the effects of St John’s wort?
It’s thought that the beneficial effects of St John’s wort stem from extracts it contains that affect neurotransmitters in the brain that are linked to anxiety and depression.
The use of St John’s wort as a treatment for depression has created controversy in Australia and throughout the world, where it is consumed in dried herb, tablet, capsule, tea or liquid form.
Like other herbal preparations, St John’s wort can cause side effects, with some users complaining of a dry mouth, dizziness, increased sensitivity to sunlight (photosensitisation), gastrointestinal symptoms and fatigue.
Does St John's wort affect other medications?
Here in Australia, St John’s wort is freely available, but preparations are regulated by the Therapeutic Goods Administration (TGA) which has warned that the strength of active ingredients may vary between preparations and that drug interactions are also possible with other medications.
Some of the drug interactions may take the form of the St John’s wort boosting the effect of the other drug which then increases the risk of adverse reactions from the other drug. Another effect St John’s wort may have is to increase the breakdown of other drugs, thus reducing their concentration in the blood and hence their effect.
Some of the drugs that St John’s wort interacts with are antidepressants, HIV medications, transplant drugs, warfarin (a blood thinning agent), some heart medications, anticonvulsants used in the treatment of epilepsy, the contraceptive pill and migraine treatments.
The TGA estimates that 60 per cent of Australians use at least one complementary health product per year, including herbal products such as St John’s wort.
Warning
Because of problems with adverse drug interactions, St John’s wort may not be suitable for everyone. Always advise your doctor or health professional if you are already taking, or intending to take, a complementary medicine or herbal preparation.
Last Reviewed: 05 July 2001
- 1. BMJ 2000; 321: 536-39.
2. J Clin Psychiatry 2000; 61 (11): 815-20.
3. Therapeutic Goods Administration Info sheet & Facts and Figures.
