Chapter 46 Placebo and nocebo effects
A remedy without any direct action on a disease, given to keep the patient happy, or to persuade the prescriber that he is doing something positive and useful, or both
The placebo effect (from the Latin ‘I will please’) is important to understand because it can have a great effect on the treatment of patients. Placebos are used and abused, but often little understood.
The emergence of placebo effects
Until recently there could be no neat distinction between drugs whose mode of action for a specific disorder was known and understood, and any other drug (Fig. 1). With the development of scientific medicine, people then began to identify active ingredients and to become more suspicious of drugs whose action was not understood. This introduced the notion that there were drugs that would treat a particular condition by a particular route and other substances that might be placebos.
However, placebos have been shown to bring about clinical improvement in many branches of medicine: surgery, the treatment of cancer, dentistry, psychiatry, paediatrics and numerous others. They can produce the same phenomena observed with other drugs:
The nocebo phenomenon
It is also possible for a drug or procedure to produce adverse effects that are not the result of any known pharmacological mechanism. These are called nocebo effects, from the Latin ‘I will harm’. In one study women who believed they were prone to heart disease were nearly four times as likely to die as women with similar risk factors who did not believe this (Eaker et al., 1992). Another large study in California found that Chinese-Americans who had a combination of birth year and disease which Chinese astrology and medicine consider ill-fated died younger than matched white controls (Phillips et al., 1993). Although effects can be severe, reported nocebo symptoms are more usually generalized and diffuse, such as drowsiness, nausea, fatigue and insomnia. In clinical trials these nocebo effects can be severe enough to lead to non-adherence, discontinuation and drop-out.
Placebos and clinical trials
In order to demonstrate the efficacy of any new treatment now, clinical trials include a placebo for comparison so that such effects can be separated from the effects of the experimental compound. These are often double-blind trials, i.e. neither the patient nor the member of staff who gives it knows which is the experimental drug and which is the placebo. This ensures that nothing can influence a patient’s expectations about the drug and, therefore, the response.
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