16.46 The placebo effect

Asian girl witch with red cloak preparing a magic potion

Has anyone ever recommended something to cure a minor ailment, or something to improve your health, because “it worked for me”? This “something” could be an expensive commercial product (like some dietary supplements), aromatherapy, a copper bracelet, a magnetic bracelet, a change in diet or an exercise regime.

The problem is that all of these things can improve your health – if you believe in them! Our minds are very powerful and can influence us in all sorts of ways. If we think of our minds as the products of our brains, this is not surprising. The brain is one of the most important organs in our bodies. But our organs do not act in isolation – they act as part of a living person.

The idea that if you believe in some health treatment it is likely to work is called the placebo effect.

Medical researchers need to know whether a new form of treatment acts directly on an illness or whether it acts because of the placebo effect. One way of doing this is to prescribe the treatment to some people and a fake treatment to others. These subjects don’t know whether they have received the real treatment or the fake (control) treatment. If significantly more (see post 16.28) of the treated group get better than the control work, then it appears that the treatment has a direct effect on the problem being treated and does not work by the placebo effect.

This type of experiment is called a blinded controlled trial. (“Controlled” because not everyone receives the real treatment; “blinded” because they don’t know whether they are in the treated or control groups.) But there is a problem. How do we know the person has got better? Normally he or she would be examined by a doctor. But doctors are human beings, like the rest of us. They are likely to expect the treated people to get better but not the people in the control group. So they may well react, subconsciously, to them in different ways. This difference in the doctor’s reaction may influence how well the person being examined feels.

This problem can be overcome by a double-blinded controlled trial in which neither the examining doctor nor the subjects of the trial know who is in the treated group and who is in the control group.

This type of trial raises all sorts of ethical problems associated with denying ill people effective treatments. But ways of overcoming such problems have been developed, to ensure that everyone gets the treatment they need when it appears to be safe (post 16.1) and effective.

I suspect that homeopathy may work by the placebo effect. In homeopathy a solution of a medicine is diluted until there are none, or very few, of the original medicine molecules left. Some people believe that the water used to dilute the medicine retains a memory of the shape of the dissolved medicine molecule. I believe this explanation is unlikely because water is a fluid in which the molecules are free to move (post 16.37). Even though water has stronger interactions between its molecules than most liquids (see post 16.45), the molecules are still able to move to the extent that water can flow. This movement of the water molecules seems to me to be inconsistent with the water retaining a memory of molecules that used to be dissolved in it.

I have been told that homeopathic medicines can work on cats and dogs who don’t know they are being treated – so homeopathic medicines must have a direct effect on the condition being treated and not work solely by the placebo effect. But the owners know that they have given their cat or dog a homeopathic remedy. If the owners didn’t believe in these remedies they wouldn’t have bought them. So they expect the cat or dog to get better. This expectation is likely to be communicated to the animal by the behaviour of the owner, in exactly the same way as a doctor may subconsciously react in different ways to a treated or a control human subject (see above).

Some people believe that homeopathy must work because some homeopathic practitioners are qualified doctors. This is really a belief that people in authority are always right. But science is a way of thinking – not a belief in authority (see What’s this blog for?). Doctors are human beings like the rest of us – they are not infallible. Do you always trust politicians, advertisers, journalists and estate agents (“realtors” in the USA)? Most of them are honest, reliable people – like most doctors. But we don’t always believe them because we know that they can make mistakes and some of them may be affected by irrational influences and even by greed.

Is there anything wrong with using placebos to treat sick people? If a placebo makes them feel better, I can’t see a fundamental objection. But we do need to be careful. Dishonest people can sell placebos to sick people, who are told they are receiving a genuine treatment, for a lot of money. The vendor may not even be dishonest – just misguided. Also an unqualified person may give a placebo to someone who has a life-threatening illness or an illness with other serious consequences. The placebo may then mask the symptoms of the serious illness and/or delay the sick person from seeking proper treatment.

I’ve no way of knowing whether or not most of the treatments that I’ve named in this post have a direct effect on illness or whether they are placebos. The reason is that most of them have not been tested by well-designed experiments like the double-blinded controlled trial described above. In some cases, this would be very difficult – most people would know whether or not they were wearing a magnetic bracelet! So, anyone who did a double-blinded controlled trial of the health benefits of wearing a magnetic bracelet, would probably be misleading him/herself – and other people. And for most of these treatments, nobody has given a convincing explanation as to why they might work.


Related posts

16.32 Faith in science
16.22 Science can’t explain everything
16.10 Expensive cars and health
16.3 Scientific proof
16.1 Drug safety


Follow-up posts
20.12 What happens in a pandemic?
20.4 Questionnaires
17.1 Its obvious




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