Trick or Treatment—The Undeniable Facts about Alternative Medicine (Electronic book text)

So far, it would be easy to think that the placebo effect is restricted to reducing the experience of pain, perhaps by increasing the patient’s pain threshold through placebo-induced will power. Such a view would underestimate the power and scope of the placebo effect, which works for a wide range of conditions, including insomnia, nausea and depression. In fact, scientists have observed real physiological changes in the body, suggesting that the placebo effect goes far beyond the patient’s mind by also impacting directly on physiology.

Because the placebo effect can be so dramatic, scientists have been keen to understand exactly how it influences a patient’s health. One theory is that it might be related to unconscious conditioning, otherwise known as the Pavlovian response, named after Ivan Pavlov. In the 1890s Pavlov noticed that dogs not only salivated at the sight of food, but also at the sight of the person who usually fed them. He considered that salivating at the sight of food was a natural or unconditioned response, but that salivating at the sight of the feeder was an unnatural or conditioned response, which existed only because the dog had come to associate the sight of the person who fed it with the provision of food. Pavlov wondered if he could create other conditioned responses, such as ringing a bell prior to the provision of food. Sure enough, after a while the conditioned dogs would salivate at the sound of the bell alone. The importance of this work is best reflected by the fact that Pavlov went on to win the Nobel Prize for Medicine in 1904.

Whilst such conditioned salivation might seem very different from the placebo effect on health, work by other Russian scientists then went on to show that even an animal’s immune response could be conditioned. Researchers worked with guinea pigs, which were known to develop a rash when injected with a certain mildly toxic substance. To see if the rash could be initiated through conditioning, they began lightly scratching the guinea pigs prior to giving an injection. Sure enough, they later discovered that merely scratching the skin and not giving the injection could stimulate the same redness and swelling. This was extraordinary — the guinea pig responded to scratching as if it were being injected with the toxin, simply because it had been conditioned to associate strongly the scratching with the consequences of the injection.

So, if the placebo effect in humans is also a conditioned response, then the explanation for its effectiveness would be that a patient simply associates getting better with, for example, seeing a doctor or taking a pill. After all, ever since childhood a patient will have visited a doctor, received a pill and then felt better. Hence, if a doctor prescribes a pill containing no active ingredient, a so-called sugar pill, then the patient might still experience a benefit due to conditioning.

Another explanation for the placebo effect is called the expectation theory. This theory holds that if we expect to benefit from a treatment, then we are more likely to do so. Whereas conditioning would exploit our unconscious minds to provoke a placebo response, the expectation theory suggests that our conscious mind might also be playing a role. The expectation theory is supported by a host of data from many lines of research, but it is still poorly understood. One possibility is that our expectations are somehow interacting with our body’s so-called acute phase response.

The acute phase response covers a range of bodily reactions, such as pain, swelling, fever, lethargy and loss of appetite. In short, the acute phase response is the umbrella term used to describe the body’s emergency defensive response to being injured. For instance, the reason that we experience pain is that our body is telling us that we have suffered an injury, and that we need to protect and nurture that part of the body. The experience of swelling is also for our own good, because it indicates an increased blood flow to the injured region, which will accelerate healing. The increased body temperature associated with fever will help kill invading bacteria and provide ideal conditions for our own immune cells. Similarly, lethargy aids recovery by encouraging us to get much-needed rest, and a loss of appetite encourages even more rest because we have suppressed the need to hunt for food. It is interesting to note that the placebo effect is particularly good at addressing issues such as pain, swelling, fever, lethargy and loss of appetite, so perhaps the placebo effect is partly the consequence of an innate ability to block the acute phase response at a fundamental level, possibly by the power of expectation.