Placebo Effect Flashcards
Placebo effect
In general, a placebo is an inert substance that has no inherent pharmacological activity. It looks, smells and tastes like the active drug with which it is compared.
An active placebo is a drug which has its own inherent effects but none for the condition that it is being given. An example of an active placebo is the use of atropine as the control drug in trials of antidepressants.
A nocebo is a placebo that produces prominent side effects.
A placebo need not always be pharmacological. It could be procedural, for example, sham electroconvulsive therapy (ECT), where the patient is anaesthetised but not given ECT.
Treatments that are perceived as being more powerful tend to have a stronger placebo effect than those that are perceived to be less so. Thus, placebo injections have more effect than oral placebos, capsules are perceived as being stronger than tablets, bright-coloured placebos are more effective than light-coloured ones larger placebos have more effect than smaller ones, and two placebos have more effect than one. Also, the status of the treating professional is directly related to the placebo effect. The same compound has been found to be more powerful if it is branded than when it is unbranded.
Among psychiatric disorders, the placebo effect has been most extensively studied in depression. Pattern analyses have shown that the improvement as a result of placebo in depression tends to be abrupt, occurs early in treatment and is less likely to persist, whereas improvement in response to antidepressants tends to be gradual, occurs later and is more likely to persist. Even among patients apparently responding to the active drug, if the pattern of improvement is consistent with a placebo response (i.e. abrupt and early), the improvement tends to be short-lived.
Placebo sag refers to a situation where the placebo effect is diminished (attenuated) with repeated use
(The placebo effect. Psychiatric Bulletin, 2006, 30, 185-188)
The following facts about placebos in the Maudsley Guidelines (and therefore are likely to come up in the exams!)
Placebo is not the same as no care (patients who maintain contact with services have a better outcome than those who receive no care)
The placebo response is greater in mild illness
The higher the placebo response rate the more difficult it is to power studies to show treatment effects
It is difficult to separate placebo effects from spontaneous remission
Patients who enter RCTs generally do so when acutely unwell. Symptoms are likely to improve in the majority irrespective of the intervention (so called ‘regression to the mean’)
The placebo response rate in published studies is increasing over time
‘Breaking the blind’ may influence outcome. The resultant ‘expectancy effect’ may explain why active placebos are more effective than inert placebos.
Not all placebos are the same. Colour, route, branding all influence the placebo effect
Placebo response is usually short lived
