Medicine man

Last week the National Institute of Clinical Excellence (Nice) reported that British GPs grossly overprescribed antidepressants such as Prozac. In 2004, 19 million prescriptions were issued for about 3.5 million UK patients at a total cost of £400m. Especially for milder forms of depression, the now well-known risks of such drugs, eg suicide, anxiety, insomnia, headaches, are greater than their benefits. Nice recommended using alternatives.

What alternatives? Officially, counselling was mentioned but many commentators felt that this was far from practical. We simply do not have nearly enough counsellors who are sufficiently trained to treat depression effectively. A spokesman for the Royal College of GPs said: "With a chronic shortage of counselling and psychotherapy ... GPs often feel that they have little choice but to prescribe antidepressants."

Obviously, we need a feasible solution to this dilemma. My advice is to reconsider St John's wort. This herbal antidepressant has been popular for some time. In Germany, where it is a prescription drug, it used to outsell Prozac by 4 to 1. But a few years ago, sales figures went into free-fall. The reason was "bad news" about its potential to interact with a host of prescription drugs. Plenty of good research has now looked into these issues in detail, and we now understand much better what is going on.

There is not a shadow of a doubt that St John's wort extracts do interact in a major way with several prescription drugs. Essentially, it speeds up both the breakdown and the elimination of these medicines. As a consequence, their blood level decreases such that the desired pharmacological effect is no longer achieved. If you are taking anticoagulants to prevent a blood clot, for instance, St John's wort could cause a stroke. If you are taking oral contraceptives, it could lead to pregnancy.

Serious consequences, no doubt, but no reason to discard St John's wort altogether. It is extremely safe provided you don't combine it with other drugs. In fact, several analyses have demonstrated that St John's wort causes no more side-effects than a placebo - it's impossible to conceive of a medicine that is less toxic than that. If you do have to take other medicines, talk to your doctor about it. As not all drugs are affected by the actions of St John's wort, it is possible that you can combine the two without any risk at all. In essence, all this means that many people with mild depression can safely take this herbal antidepressant.

And what about efficacy? Does St John's wort really work? Yes it does. Even though there have been a couple of American studies that cast doubt on its effectiveness, the totality of the data from rigorous clinical trials is indisputably in favour of St John's wort. A report just published pooled the data from all 30 top-quality trials. When tested against placebo, St John's wort extracts were clearly very effective in reducing the symptoms of depression. When tested against conventional antidepressants, they proved to be just as good. Most remarkably, in the sub-group of those patients suffering from mild to moderate depression, St John's wort was significantly superior to its synthetic competitors. About 2,000 patients were included in each comparison, which means we can be fairly confident about the reliability of these findings.

The data on St John's wort are, I think, better and more convincing than the evidence for any other complementary therapy used for any disease or symptom. Taken on its own, this herbal antidepressant is demonstrably safe and effective. Provided you use a good-quality extract and don't under-dose (900mg to 1,800mg of a standardised extract is what most of the clinical studies used but some UK supplements only contain half of that dose), the benefits are significant and clearly outweigh the risks.

If St John's wort were a synthetic drug, no doubt, all government bodies would recommend it. Now that we know of the problems with synthetic antidepressants, should we not take an unbiased view and reconsider the issue?

· Edzard Ernst is professor of complementary medicine at the Peninsula medicine school at the universities of Exeter and Plymouth.

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