Placebo effects in pain

A placebo effect is always present and active in any therapeutic interaction. It can occur with no or limited intention, or awareness of the practitioner or the patient. The placebo effect describes the component of a therapeutic response attributable to the context in which an intervention is delivered.

The placebo effect should be distinguished from a placebo intervention. A placebo intervention is commonly used in clinical trials to mimic the therapeutic context, in order to gauge the effect of the ‘active’ intervention alone.

The placebo effect can be influenced by the practitioner’s behaviour, the practitioner-patient relationship, and the patient’s previous experiences and conditioning. These factors may influence the patient’s expectations of a therapeutic intervention and impact the intervention’s efficacy.

The placebo effect can be utilised in clinical practice by enhancing the patient’s expectations by setting realistic expectations, reinforcing positive experiences, clarifying misconceptions and interacting personally with the patient. Positive expectations can trigger endogenous pain inhibition via opioid and nonopioid mechanisms. Do not promote treatments with limited efficacy on the basis that they will produce a placebo effect; this is deceptive, places the therapeutic relationship at risk and breaches informed consent (and informed assent in minors).

The nocebo effect describes a reduction in clinical benefit due to negative patient expectations of an intervention or a prognosis. In clinical practice, practitioners can minimise the nocebo effect by attempting to reduce negative expectations.