Even some rationalists keep an open mind about the efficacy – or lack of it – of homeopathy. Terry Sanderson’s review of a BBC2 Horizon programme on the subject last issue called it “money for old rope”. In this article, John Allen puts homeopathy under his microscope.
The reputation of homeopathy has suffered a severe battering as a result of recent clinical and laboratory studies. The latest of these involved a test of the effectiveness of arnica, probably the most widely used homeopathic remedy.
Homeopaths claim that arnica eases pain, reduces swelling and soothes bruises. To test these claims, a group of researchers at Exeter University set up a clinical trial on patients undergoing hand surgery for a painful condition caused by a compressed nerve. The Exeter study used two groups of patients, who received either a low or high dose of arnica. A third – control – group of patients received a “placebo” pill identical in appearance to arnica but containing no medicine at all.
After surgery patient ratings of pain and objective measures of bruising and swelling in the three groups were compared. Despite the longstanding claims made for arnica, the Exeter team found that it had no more effect than the placebo pill.
Why the use of a control group and a placebo? Researchers have known for decades that in many illnesses a significant proportion of patients show improvements in their condition because of the body’s ability to repair itself or fight off infections. Others recover because they experience a psychological lift from the medical attention they receive. There can be many reasons for this, ranging from what is known as “the instillation of hope” through to improved response of the immune system engendered, perhaps, by feelings of optimism and a sense of some control over the illness. Only if the medicine under test produces significantly better improvements than the placebo do researchers conclude the medicine has a really beneficial effect.
The arnica study is by no means the first to put the claims of homeopathy to the test. There have been numerous attempts to evaluate the claims of homeopathy. Many of these have been little more than anecdotal reports of patients recovering after receiving treatment from homeopaths. Others, however, have attempted to gather objective evidence of symptom relief and have involved the proper use of control groups and placebos. Interestingly, when the investigators are themselves homeopaths, the results of these tests tend to be positive. However, when tests are conducted by independent researchers who have conducted well-designed clinical trials, the results tend to be much less impressive.
Two years ago an extensive review of these studies concluded: “There is some evidence that homeopathic remedies are more effective than placebos; however, the strength of this evidence is low because of the low methodological quality of the trials. Studies of high methodological quality were more likely to be negative than the lower quality studies.” In essence, the reviewers are saying the better the study the greater the chance it shows homeopathy to have no effect.
In fact, there are good reasons to suppose that homeopaths should achieve slightly better results than placebos even though the remedy itself is ineffective. This apparently paradoxical argument arises from the way in which homeopaths interact with their patients. If you go to a traditional homeopath you are likely to be asked questions not only about your symptoms but also about your diet, lifestyle and general state of mind. Answers to all these questions will influence the homeopath’s choice of remedy. Typically, clinical interviews last well over an hour and may be repeated several times. Psychologists know that, when health workers spend time with patients and express interest and encouragement, patients can benefit significantly. Being listened to and being encouraged to explore feelings by another person makes most of us feel better, even if only temporarily. So important are these listening skills that health psychologists are now involved in the training of medical students both at undergraduate and postgraduate levels.
So we ought not to be surprised if a few poorly designed studies show positive results. They may well be the ones that involve good listening and counselling skills. Claims about the medicinal effects of homeopathic remedies could be entirely false, but some homeopaths may achieve encouraging results because they are good at “people skills”. So, if you fall ill, you would be better off going to a doctor who practises evidence-based medicine and has a good “bedside manner”.
However, the lack of unequivocal evidence about its effectiveness is not the only reason for doubting the claims of homeopathy. When Samuel Hahnemann pioneered homeopathy in the late eighteenth century, he enunciated an extraordinary principle known as the Law of Infinitesimals. This states that the more dilute a substance is the better it works at alleviating the symptoms of illness. Hahnemann adopted this principle because many of the remedies he used were poisons, even when given in relatively small amounts.
The dilutions typically used by homeopaths today are enormous. In fact, so extreme are they that the remedies supplied to patients are extremely unlikely to contain any of the original medicinal ingredient. The physicist Robert Park has calculated that at typical dilutions one would have to drink 7,874 gallons (or about 35,795 litres) of a homeopathic solution to get a single molecule of the putative medicine!
Yet the reasons for scepticism do not end here. In order to counter the doubts raised by the Law of Infinitesimals, the advocates of homeopathy have made even more extraordinary claims. Accepting that many homeopathic remedies contain no molecules of the original medicine, they have argued that the solvent used in the process of dilution (usually water or alcohol) “remembers” the presence of the medicine. According to this argument it is the “memory” that produces beneficial effects. When the French homeopath Jacques Benveniste published his research on “water memory” in the journal Nature in 1988 it caused a storm of controversy. In response to his claims a team of eminent scientists conducted a painstaking analysis of Benveniste’s work. The outcome was a complete failure to find evidence for the “water memory” theory. Subsequently, other workers have claimed to find evidence of “water memory” and these claims prompted James Randi to join the BBC’s Horizon team in an attempt to replicate their results. Broadcast last November, the programme documented a test that incorporated a number of crucial controls for unconscious bias and poor laboratory practice thought to have been present in earlier studies. The outcome? Again, a resounding failure to find any evidence of “water memory”.
Despite all these reasons for profound doubts about homeopathy, belief in its effectiveness persists in the minds of many. The sales of homeopathic remedies worldwide is a multi-million-pound business and some homeopaths make wildly optimistic claims, including the ability to cure HIV/AIDS and hepatitis B. So why does belief in homeopathy continue?
One reason stems from a flaw in the way in which we perceive causality. The psychologist and rationalist James Alcock has pointed out that our perception of causal links between events is prone to a common error. Suppose a friend or relative becomes ill and takes a pill. They then quickly recover. It is very tempting to conclude that the pill caused the recovery. Yet this may be a completely erroneous conclusion.
Alcock tells of a personal experience that well illustrates the flaw. Several years ago he was attending a scientific meeting in China when he developed a very sore throat. He thought he probably had a bronchial infection. Eventually, he sought help and was taken to the outpatient clinic at Beijing Hospital, where he was given two medications. The first was the antibiotic erythromycin. The second was a traditional Chinese remedy for throat problems, the principal ingredient of which was snake bile! Unsurprisingly, Alcock declined to use it and took the erythromycin instead. In a few days his sore throat cleared up and he congratulated himself for making the rational choice.
That would have been the end of the matter but, upon his return from China, his experience was reported in the Skeptical Inquirer. A few months later a physician responded in a letter to the editor, in which he pointed out that all too often bronchial infections are caused by viruses and are therefore not treatable with antibiotics. If Alcock’s sore throat has been caused by a viral infection the antibiotic would have been completely ineffective.
Alcock had done what most of us would have done. He took a medicine he believed in and got better. What could be more natural than to conclude that the medicine made him better? Yet in all likelihood it had no effect at all! His own immune system had done the trick on its own. The only way really to evaluate the efficacy of a medicine is by carefully controlled clinical testing. We should be very wary of drawing the wrong conclusions from inadequate evidence, especially when it takes the form of “someone I know took a homeopathic medicine and got better, therefore it must work”. The truth is there are probably several other competing explanations for the same observation.