Placebo and nocebo effects

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


(Penguin Medical Encyclopaedia)


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.


image

Fig. 1 Drugs and mode of action.


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:


image Habituation (a tendency to increase the dose over time)

image Withdrawal symptoms

image Dependence (an inability to stop taking them without psychiatric help)

image Inverse relationship between severity of symptom and efficacy of placebo


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.



Types of placebo



image Pure placebo: thought to contain no active ingredient, for example, a sugar pill.

image Impure placebo: contains an active ingredient, but one which is not known to have any effect on the condition being treated, e.g. a vitamin C tablet being given for headache.

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Jun 10, 2016 | Posted by in PSYCHOLOGY | Comments Off on Placebo and nocebo effects

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