placebo effect

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n.

The beneficial effect in a patient following a particular treatment that arises from the patient's expectations concerning the treatment rather than from the treatment itself.

n

The real or imagined effect of a placebo, which may actually be the same effect ordinarily associated with the administration of a therapeutically active agent.

Definition

A placebo effect occurs when a treatment or medication with no therapeutic value (a placebo) is administered to a patient and the patient's symptoms improve. The patient believes and expects that the treatment is going to work, therefore it does. The placebo effect is also a factor to some degree in clinically effective therapies, and explains why patients respond better than others to treatment despite similar symptoms and illnesses.

Origins

The word placebo is from the Latin "I shall please." Throughout most of medical history, the placebo effect was the principal treatment physicians offered their patients—e.g. reassurance, attention, and belief in treatment would mobilize patients' internal powers to fight their illnesses. This is still true in indigenous cultures using shamanistic healing which places healing power in objects and rituals. In fact placebos are sometimes called sham treatments.

Placebos were used throughout the nineteenth century in blind assessments of medical treatments. These blind assessments were created to test controversial medical treatments of the time (e.g. mesmerism and homeopathy), and involved using a blindfold on or withholding information from patients so they were unaware of the exact nature of the treatment being studied. For example, in blind assessments of homeopathy conducted in 1834 in France, homeopathic remedies were replaced with an inert placebo substance without the patient's knowledge. These blind assessments were the forerunners to today's double-blind randomized controlled trials used in drug development and in the study of other therapeutic techniques.

According to some medical historians, from the early 1800s through as late as World War II, placebos (usually in the form of sugar pills or saline injections) were regularly prescribed to up to 80% of patients. Doctors used placebos to appease patients when no effective treatment for their symptoms was available, or prescribed placebos to patients they perceived as difficult.

The first documented American clinical study using placebos was conducted in the late 1920s. In 1937 scientists at Cornell University Medical School published a study on an angina drug that used a placebo and blind assessment techniques. They found that the patients who were given a placebo instead of the angina drug experienced an improvement of symptoms. This was the first published account in the United States that discussed the possible therapeutic value of the placebo effect.

Benefits

The placebo effect is usually positive by its nature, because it indicates that a patient believes in the therapy, and the therapy is having some sort of a beneficial effect. The placebo effect has been documented in a wide variety of diseases and disorders. Certain conditions such as headaches, arthritis, and hot flashes are especially responsive to placebos, as are some individuals.

Description

Every available medical treatment is subject to the placebo effect. If a patient believes the therapy will benefit them, it usually will to some degree. Even if the placebo does not improve the symptoms directly, the peace of mind a patient may feel after taking a treatment they believe will help them is often enough to encourage a sense of improved well-being. This is why controlled, scientific studies are so crucial to determining the actual clinical efficacy of medications and therapies.

The person prescribing the placebo treatment may also have an impact on the effect it has on the patient. For example, a doctor's enthusiasm about a new treatment may heighten its placebo effect for his patient. In addition, if a healthcare provider is perceived as a trusted, well-respected figure by the patient, the patient may experience benefits from any treatments the provider prescribes.

Placebos are often used in scientific trials of new medications and treatments to determine their efficacy. A randomly selected group of study subjects known as the control group are given placebo medication (usually a sugar or water-based substance) or treatment while the rest of the subjects are administered the actual therapy. The patients do not know which group they are in during the study, and the researchers and study authors do not know which subjects are in which group (hence the term double-blind). This helps researchers to determine if new treatments work because they are clinically effective, or because the subjects believe they will work.

Overall, the average placebo effect is 33%, though it can range lower and higher. Therefore, to demonstrate that a treatment, procedure, or medication is effective, a trial has to show that it does significantly better than the placebo given to a control group. For example, a study of single-remedy homeopathy was conducted with a group of 487 patients with an influenza-like syndrome. Patients treated with a single, non-individualized remedy were 70% more likely to have recovered within 48 hours than those receiving the placebo.

Preparations

Placebos only have therapeutic value if the patient believes they will work. If an individual chooses a healthcare provider that they trust, respect, and feel comfortable with, there may be a more likely chance that treatments the provider recommends (whether clinically effective or unproven) will be perceived as having a more beneficial effect.

The use of a placebo in scientific studies requires informed consent of the entire population of subjects. The study subjects must know that they have a 50/50 chance of receiving a placebo treatment instead of the treatment under investigation.

Precautions

There are ethical issues involved with administering placebos to patients if the healthcare provider knows there is no therapeutic value to the treatment and other available treatments could possibly benefit the patient. For patients with progressive or life-threatening illnesses, taking a medication or therapy with no clinical value other than its placebo effect can be harmful if it causes them to neglect other proven treatments that could improve their condition.

Some clinical trials of surgical procedures require the placebo, or control subjects to undergo what is essentially unnecessary surgery, involving incisions and other invasive procedures while the final therapeutic portion of the procedure is withheld (the placebo). Although this is standard scientific procedure currently recommended by the U.S. Food and Drug Administration (FDA) for the approval of new medical procedures and devices, it is also commonly accepted knowledge that unnecessary surgery is never beneficial to a patient and can result in serious complications such as infection, hemorrhaging, and conceivably even death.

Side Effects

The placebo effect can have a negative influence also, a nocebo. If a placebo is given that the patient believes to be harmful to their health in some way, he or she may develop symptoms appropriate to this belief. A toxic or negative placebo suggests the great degree to which attitudes and expectations can affect one's state of health or course of an illness. People who think they have been cursed or a victim of voodoo have been known to die.

Research & General Acceptance

The placebo effect is a well-known phenomena in the scientific community, and clinical trials and other scientific studies are built around the theory. Ethical concerns can arise when there is a risk that patients are not getting the potentially life-saving treatments they need. In some cases, the placebo effect is enough to compensate for this. For example, a study published in the Archives of General Psychiatry found that in 45 controlled trials of antidepressants, subjects in the control group experienced a significant positive therapeutic effect with the placebo only. In cases of treatments involving potentially fatal diseases such as cancer and AIDS, the ethical implications of placebo use may not be as clear-cut.

Surgical placebo procedures, which are a relatively new type of clinical study, are not as universally accepted as placebo drug trials. There is a heated debate in the medical community over the value of such studies. However, the use of placebo surgery for controlled clinical trials is endorsed by the National Institutes of Health, the medical research arm of the U.S. Department of Health and Human Services.

Resources

Books

Harrington, Anne. The Placebo Effect: An Interdisciplinary Exploration. Cambridge, MA: Harvard University Press, 1999.

Shapiro, Arthur K., and Elaine Shapiro. The Powerful Placebo: From Ancient Priest to Modern Physician. Baltimore, MD: John Hopkins University Press, 1997.

Periodicals

Kaptchuk, Ted J. "Intentional Ignorance: A History of Blind Assessment and Placebo Controls in Medicine." Bulletin of the History of Medicine 72, no. 3 (1998):389-433.

[Article by: Paula Ford-Martin]

A positive response to a placebo, similar to that of an active substance, brought about by a person's expectations of the placebo. The placebo effect is well established in sport and is often used as an ergogenic aid. Placebo salves with no pharmacologically active ingredients have been used to relieve muscle fatigue. This demonstrates that although a placebo may have a psychological origin, it can produce a real physical response.

When people are unwell, they will often begin to recover just as soon as they receive medical attention, but before the treatment could have any direct effect and even when the treatment is a sham. Mere belief that recovery is coming can by itself bring the recovery about.

This is the placebo effect (named in the Middle Ages after the professional mourners at a funeral who were paid to sing vespers for the dead, beginning 'Placebo Domino ...'). The essayist Michel de Montaigne, writing in 1572, noted that 'there are men on whom the mere sight of medicine is operative', and he went on to describe what would now be considered a textbook case:

[There was] a man who was sickly and subject to [kidney] stone who often resorted to enemas, which he had made up for him by physicians, and none of the usual formalities were omitted... . Imagine him then, lying on his stomach, with all the motions gone through except that no application has been made! This ceremonial over, the apothecary would retire, and the patient would be treated just as if he had taken the enema; the effect was the same as if he actually had... . When, to save the expense, the patient's wife tried sometimes to make do with warm water, the result betrayed the fraud; this method was found useless and they had to return to the first. Recent scientific studies, comparing placebo with no-placebo, as Montaigne did here, have confirmed the reality of the phenomenon. The effects appear to be strongest and most reliable in the treatment of pain, where in both clinical and laboratory settings placebos of all kinds — sugar pills, cold creams, saline injections, fake ultrasound, even mere words, when convincingly presented as medical painkillers — have been found to bring significant relief. But placebos can also be effective in the treatment of a range of other illnesses, including stomach ulcers, heart disease, depression, and Parkinson's disease. As Robert Buckman has summed it up: 'Placebos are extraordinary drugs. They seem to have some effect on almost every symptom known to mankind, and work in at least a third of patients and sometimes in up to 60 per cent. They have no serious side-effects and cannot be given in overdose. In short they hold the prize for the most adaptable, protean, effective, safe and cheap drugs in the world's pharmacopoeia.'

Still, much remains to be discovered about how and why placebos work. What exactly is the message the placebo gives the patient, and by what perceptual routes does it arrive? How does this message and the meaning that is attached to it affect the patient's specific expectations and/or general mood? How do these changes in what the patient thinks (particularly) or feels (more generally) about his ailment activate the physiological mechanisms that lead to recovery? And, then, the deeper question about evolutionary design: what biological advantage can there be in having the mind control the body's healing systems in this way?

People rely on a variety of sources of information for foretelling the future. It is clear that the placebo's message — to the effect that 'this treatment will soon make you better' — can be conveyed by any or all of them: learned associations, explicit instruction, rational argument, magical reasoning, trust in authority, and, of particular importance, subtle social cues of the kind called 'bedside manner' (so that, for example, the same placebo pill may work consistently better when administered by one doctor than another). But, by whatever route the message comes, the patient must have the right mindset to receive it. There are large cross-cultural differences in placebo responsiveness, which, though little understood, promise to throw light on how local attitudes to medicine and the symbolism of the body may enable or disable the 'meaning response'(Moerman 2002). For example, placebo medicine works powerfully for the treatment of stomach ulcers in Germany (60 per cent healing rate), but hardly at all in Brazil (7 per cent); yet for the treatment of hypertension, placebo medicine is less effective in Germany than elsewhere.

Placebo treatments tend to have results specific to the particular ailment and the part of the body to which they are applied (for example, placebo pain-relieving cream applied to the left hand does not relieve pain on the right). So the effects cannot be being mediated entirely through changes in the patient's general mood. Rather, the patient's expectations that the treatment will work (like a real medicine) to help with the particular problem it addresses must be being channelled into a relatively narrow and 'appropriate' response.

How does the mind talk to the body's healing systems in such specific ways? Recent research in neuroimmunology has uncovered intimate links between the central nervous system and the immune system, with several kinds of neurotransmitters doubling as signallers for immune activation and vice versa (Evans 2003). There is therefore plenty of scope for cross-talk. However, one chemical pathway in particular — the endogenous opiates — very likely plays a central role: for it has been found that placebo treatments for pain become completely ineffective if the patient is also given the drug naloxone, which blocks endogenous opiates from working. What is more, endogenous opiates are known also to be involved in the regulation of inflammation, nausea, wound healing, and antibody production. So it is possible — but as yet unproved — that endogenous opiates are responsible for mediating placebo effects across the board: indeed that they provide a kind of lingua franca for mind–body interaction in relation to healing.

No doubt we shall soon have answers to these questions about how placebos work, but there will remain the larger question: why.

When people recover from illness as a result of placebo treatments, it is of course their own healing systems that are doing the job. Placebo cure is self-cure. But if the capacity for self-cure is latent, then why is it not used immediately? If people can get better by their own efforts, why don't they just get on with it as soon as they get sick — without having to wait, as it were, for outside permission? Why should the mind be allowed to have such influence, when the net result is, if anything, to put a brake on healing?

This paradox has to be resolved by considering the placebo effect in a broader evolutionary context (Humphrey 2002).

Long before medicines or doctors came on the scene, human beings had already developed a fine capacity for looking after their own health: by mounting defences such as pain and fever, by actively attacking infections, by repairing bone and tissue damage, by indulging in sickness behaviours, and so on. However none of these measures is free of cost (immune resources are expensive, pain is debilitating, acting sick is time wasting, etc.). So it has been essential to have some kind of internal 'health management system' in place, to ensure that the way the body responds to any particular threat is nearly optimal.

Sometimes, for example, it would be best for a sick person to get well as rapidly as possible, throwing off defences such as pain and mounting a full-scale immune response, but at other times it might be more prudent to remain unwell and out of action and to conserve resources for later use. As a general rule (and of crucial importance for the story of placebos): the brighter the prospects for a rapid recovery, the less to be gained from playing safe and remaining sick.

But this has meant that the health management system has needed to take account, so far as possible, of any intelligence available to the sick person about what the future holds. Relevant information would include the nature of the threat, the costs of the defensive measure, the prospects for spontaneous remission, evidence of how other people are faring, the presence of social support, and so on. The mind therefore has had to become an adjunct to the healing system — precisely so as to gather this intelligence.

In the past all kinds of environmental information would be brought to bear. And no doubt they still are. But today, the medicalization of sickness has changed the picture. For it means there will often be a novel and even overriding piece of information to take into account. People have learned — their culture has taught them — that nothing is a better predictor of how things will turn out when they are sick (whether the pain will ease, whether the infection will abate, whether they will be nursed back to health, etc.) than the presence of doctors, medicines, and so on.

Yet human beings remain tied to their evolutionary heritage. And so, today, the very prospect of medical attention — the patient's belief in it — works its magic for the simple reason, stemming from the general rule above, that for most of human history, once a sick person has had cause to think that he will soon be safe and well, he has had just the excuse he needs to bring on his own recovery as fast as possible.

(Published 2004)

— Nicholas Humphrey

Bibliography
• Buckman, R., and Sabbagh, K. (1993). Magic or Medicine: An Investigation of Healing and Healers.
• Evans, D. (2003). The Belief Effect.
• Humphrey, N. (2002). 'Great expectations: the evolutionary psychology of faith healing and the placebo response'. In The Mind Made Flesh: Essays from the Frontiers of Psychology and Evolution.
• Moerman, D. (2002). The Meaning Response: Rethinking the Placebo Effect.
• Montaigne, M. de (1572). Essays. (Trans. J. M. Cohen, 1958.)

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