Placebo analgesia makes individuals experience relief of their pain simply by virtue of the anticipation of a benefit. A reduction of pain can occur also when placebos follow the administration of active and effective painkillers. In fact, studies indicate that placebos mimic the action of active treatments and promote the endogenous release of opioids in both humans and animals. Finally, social support and observational learning also lead to analgesic effects. Thus, different psychological factors and situations induce expectations of analgesia facilitating the activation of the top-down systems for pain control along with the release of endogenous mediators crucially involved in placebo-induced benefits. Recent scientific investigation in the field of brain imaging is opening new avenues to understanding the cognitive mechanisms and neurobiological substrates of expectation-induced pain modulation. Gaining deeper knowledge of top-down mechanisms of pain modulation has enormous implications for personalizing and optimizing pain management.
Trial registration: ClinicalTrials.gov NCT01328561.