St John’s Wort: The Paradox of a Herbal Medicine

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SJWDoctors have recently come under fire for prescribing the herbal remedy St John’s wort alongside other drugs, which could result in harmful effects. We clearly need to be more aware of these adverse interactions, but St John’s wort could still be a useful treatment for depression.

A study published last week in the Journal of Alternative and Complementary Medicine has raised concerns about the relaxed attitude many doctors seem to have when prescribing the medicinal herb St John’s wort. The drug is commonly taken to relieve symptoms of depression, and is available over-the counter in many countries. Yet many mistakenly believe that as a “herbal remedy”, St John’s wort must be perfectly safe.

Unfortunately, this is not always the case. In fact, St John’s wort can profoundly affect how other drugs are processed by the body: it increases the activity of certain enzymes and other proteins involved in drug metabolism and absorption. This means that some drugs are actually processed faster if St John’s wort is also being taken, decreasing their availability in the body. Medications that could be affected in this way include some anti-anxiety drugs, antiretrovirals used to treat HIV, blood thinners and oral contraceptives.

Like other antidepressants, St John’s wort also raises the level of serotonin in the nervous system. If other serotonin-raising drugs are taken alongside it, serotonin activity can become too high, effectively poisoning patients – a condition known as serotonin syndrome. This can produce a drastic rise in temperature, blood pressure and heart rate that could culminate in shock.

So you would hope that doctors were not prescribing these kinds of drugs alongside St John’s wort. This is what the study, conducted at Wake Forest Baptist Medical Center, sought to find out. Researchers examined records of visits to doctors’ surgeries in the United States between 1993 and 2010. Worryingly, they found that for almost a third of visits in which St John’s wort was prescribed, doctors also prescribed a drug that could potentially interact with St John’s wort. The most common of these were other serotonin-raising antidepressants, but anti-anxiety drugs, anticoagulants, statins and other drugs were also prescribed – all medications which could be rendered ineffective if taken with St John’s wort.

Contrary to many reports, this study hasn’t “discovered” that St John’s wort interacts with other drugs: this has been known for years, making it even more disturbing that so many patients are being prescribed these drugs at the same time. It’s clearly vital that both doctors and patients know about these potential interactions, and hopefully this study can do its part to increase awareness.

An Alternative Medicine?
Some commentators have used the publication of this study as an opportunity to rubbish St John’s wort as an antidepressant drug. An article on Science 2.0, for example, implies that St John’s wort has never been found effective in double-blind trials, and goes as far as to call its users “gullible”.

In fact, the evidence suggests that for mild-to-moderate depression, St John’s wort may work as well as the “standard” antidepressants. A 2008 Cochrane review of randomised double-blind trials found that when data from all of these studies were considered together, St John’s wort extracts were more effective than placebo at reducing measures of depression. And when compared to SSRIs or other antidepressants, St John’s wort performed just as well at treating symptoms of depression. If that’s not enough, St John’s wort was better tolerated than the other antidepressants, resulting in fewer people discontinuing treatment. Other studies since then have also supported the use of St John’s wort in treating depression.

It is important to be sceptical when it comes to medical research – there is a lot of quack medicine out there! – but part of critically analysing evidence is being open to surprising results. There are still some unanswered questions about the effectiveness of St John’s wort (for example, trials from some countries seem to show more positive results than others), but there is fairly good evidence that it may be a useful antidepressant, and it certainly warrants further study. Just as its status as a “herbal medicine” might convince doctors or patients that St John’s wort is safe, so it seems to make others reluctant to even recognise its potential as a legitimate drug.

Quality Control
There is a pretty major caveat to all of this. Laboratory studies generally use specific preparations of St John’s wort, standardised to contain particular quantities of the active ingredients, hyperforin or hypericin. But, in the UK at least, these standardised preparations are hard to come by. That bottle of St John’s wort you get from Holland and Barrett may be very different from the drugs used in the literature. In fact, the manufacturers may not even know how much of the active ingredient it contains: all that is required to register a herbal remedy in the UK is evidence that the drug is used traditionally, not that it actually works!

St John’s wort is stuck in a strange place. It is not receiving the academic attention that it seems to deserve, but at the same time is being sold with little regulation and in many cases prescribed carelessly. It’s time we started taking this herb more seriously.

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Matthew Warren
Matthew Warren is a DPhil student in the Department of Psychiatry, University of Oxford, studying how antidepressant treatment affects the way people process emotional information.

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