Placebo Effect

Placebo effect

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. The placebo effect is the observable improvement seen when a patient takes a placebo. The placebo effect results from patient related factors such as expectations rather than due to the placebo itself which is inert. Where placebo's result in negative effects (due to patient related factors) this is termed the nocebo effect. An active placebo is a treatment with a chemical activity that mimics the side effects of the drug that is being tested in a clinical trial. Active placebos are sometimes, but not always, used in clinical trials to prevent unblinding of the drug versus the placebo control group.

Placebo effect contd..

A placebo need not always be pharmacological. It could be procedural, eg. 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.

Placebo effect contd...

Among psychiatric disorders, the placebo effect has been most extensively studied in depression. 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 pts 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

Facts about placebo

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.