The Mysterious Placebo

You feel a migraine coming on and take a 50 mg tablet of sumatriptan. You know from experience that sumatriptan works for you. While your headache won't go away completely, you'll improve enough within an hour or so that you can continue to function.

Suppose someone had secretly replaced your sumatriptan with a look-alike tablet that contained only flour. Would you know the difference?

You might not. Because of a phenomenon known as the placebo effect, you might get just as much pain relief from the flour pill as from the real drug.

In studies of pain-relief medicines, about one-third of people given a dummy (placebo) medicine will report improvement. The actual percentage can vary considerably from study to study, but it is usually substantial.

In mind-body medicine, the placebo effect is credited to the self-healing powers of the mind, to the individual’s belief in and desire for cure. The individual's beliefs and expectations certainly play a part, but there are more down-to-earth explanations for the placebo effect that should also be considered.

Pain intensity can vary from one moment to another. For chronic pain conditions and some chronic diseases, such as lupus, psoriasis or multiple sclerosis, there are often alternating cycles of improving and worsening symptoms. Just by chance, you might start an effective drug when you are entering a phase of worsening symptoms and decide it is ineffective, since you have no way of knowing that your symptoms would be worse without it. This is one of the reasons why pain specialists often urge their patients to give a new medication a longer trial, even if it doesn't seem to be helping right away. Or, you might take an ineffective drug during a cycle of milder illness and believe that it has helped you. So, sometimes a placebo appears to have miraculous powers when the illness was improving on its own.

From childhood on, we've learned to associate relief with a pill, capsule or injection. This is partly a conscious expectation, but it can be unconscious as well. Decades of experiments with animals have shown that they can be conditioned to respond in specific ways to a given signal or stimulus. The most famous example is Pavlov's experiments with conditioning dogs to associate the sound of a bell with food. After many such experiences, they would begin to salivate when they heard the bell, before the food appeared. Other experiments with animals have produced results very similar to a placebo effect, where the animal's nervous system learned to respond in a particular way to a pill or other stimulus.

If you have already learned, consciously and unconsciously, to expect migraine relief from a little white tablet, then you might well get comparable relief from the flour pill that looked just like it. These placebo effects tend not to last, however. If all the pills in your prescription had been changed, you might get progressively less relief as you continued to take the placebo tablets.

Expectations can affect response to an active drug. Two British studies examined the effectiveness of acetaminophen for relieving pain after childbirth. The first study compared acetaminophen to a placebo; the second study, done in the same hospital ward with similar patients, compared acetaminophen to another pain reliever, naproxen. The women in the first study, who knew that they had a 50-50 chance of being given a placebo, reported less pain relief from taking acetaminophen than the women in the second study, who knew that they were going to be given one of two effective pain relievers.

Our powerful expectations are partners in helping medication work. Besides pills and capsules, the whole experience of seeking and getting medical attention is thought to have a potential placebo effect. The white-coated nurses and doctors, the diplomas on the wall, the examination table, the familiar instruments, and the authoritative diagnosis can all have an impact in making the person feel better that something is being done--even before any medication is prescribed. So the next time you are thumbing through old magazines in the waiting room, think: you might actually be getting help already.