Biological, clinical, and ethical advances of placebo effects

Abstract

For many years, placebos have been defined by their inert content and their use as controls in clinical trials and treatments in clinical practice. Recent research shows that placebo effects are genuine psychobiological events attributable to the overall therapeutic context, and that these effects can be robust in both laboratory and clinical settings. There is also evidence that placebo effects can exist in clinical practice, even if no placebo is given. Further promotion and integration of laboratory and clinical research will allow advances in the ethical use of placebo mechanisms that are inherent in routine clinical care, and encourage the use of treatments that stimulate placebo effects.

Figure 1

The principal placebo mechanisms that have been unraveled across different medical conditions and systems/apparatuses

Figure 2

Social stimuli around the treatment may activate, through expectation and/or conditioning mechanisms, a number of receptorial pathways in different diseases and therapeutic interventions (the involvement of 5-HT receptors in hormonal responses and depression is not definitive). These receptors are the same to which different drugs bind, thus indicating that psychosocial factors are capable of modulating the action of drugs. This interference has profound implications for our understanding of drug action: when a drug is given, the very act of administering it (i.e., the psychosocial context) may perturb the system and change the response to the drug. From : Benedetti (2008) Annu Rev Pharmacol Toxicol

Figure 3

In routine clinical practice, any treatment has a specific and a non-specific effect. The non-specific effect may come from the mere knowledge that a treatment is being given. The effectiveness of the active treatment can be assessed either by eliminating its specific effect (placebo study) or by eliminating the non-specific effects (hidden treatment). From: Colloca et al. (2004) Lancet Neurol

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Panel 2

Contributions of the psychosocial context surrounding the patient (or placebo component of a given therapy) to the overall response