Placebo effect (and placebos)

The placebo effect is the finding that often the simple psychological expectation that something will help reduces distress, improves function and even reduces mortality in serious physical illnesses: even when the “something” is inert. Hence the term “placebo” has come to be attached to the practice of giving something known to have no effect on the condition of interest as a control arm in a controlled, comparative trial.

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The term comes from the Latin, it means “I will please”. A more general term is “expectancy effect” and there is a negative version of it: the finding that when people are given an inert tablet some experience “negative side effects” a higher rate than people having nothing at all.

Quite often even in pharmacological trials it can be difficult to conceal which tablet is which, for example, many traditional antidepressants cause a dry mouth for the majority of those who take a typical dose. This has led to use of “active placebos”: for example a tablet that causes a dry mouth but is thought not to have antidepressant properties.

Try also … #

Randomised Controlled Trials (RCTs)
Double Blind Controlled Trials (DBRCTs)
Hierarchy of evidence (and web of evidence)
ESTs (Empirically Supported Treatments)

Chapters #

Chapter 10.

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