How Placebos Change the Patient's Brain

Abstract

Although placebos have long been considered a nuisance in clinical research, today they represent an active and productive field of research and, because of the involvement of many mechanisms, the study of the placebo effect can actually be viewed as a melting pot of concepts and ideas for neuroscience. Indeed, there exists not a single but many placebo effects, with different mechanisms and in different systems, medical conditions, and therapeutic interventions. For example, brain mechanisms of expectation, anxiety, and reward are all involved, as well as a variety of learning phenomena, such as Pavlovian conditioning, cognitive, and social learning. There is also some experimental evidence of different genetic variants in placebo responsiveness. The most productive models to better understand the neurobiology of the placebo effect are pain and Parkinson's disease. In these medical conditions, the neural networks that are involved have been identified: that is, the opioidergic-cholecystokinergic-dopaminergic modulatory network in pain and part of the basal ganglia circuitry in Parkinson's disease. Important clinical implications emerge from these recent advances in placebo research. First, as the placebo effect is basically a psychosocial context effect, these data indicate that different social stimuli, such as words and rituals of the therapeutic act, may change the chemistry and circuitry of the patient's brain. Second, the mechanisms that are activated by placebos are the same as those activated by drugs, which suggests a cognitive/affective interference with drug action. Third, if prefrontal functioning is impaired, placebo responses are reduced or totally lacking, as occurs in dementia of the Alzheimer's type.

“I know it’s changed”: a mixed-methods study of the meaning of Global Perceived Effect in chronic neck pain patients

“…In the absence of clearly defined causal mechanisms for neck and other chronic musculoskeletal pain conditions, we are unable to judge with certainty whether or not patients are right or wrong; however, while the identification of a definitive ''cause'' may provide relief for some patients [24], the labeling effect imparted by a diagnosis and the notion that a condition cannot be resolved may also prove problematic. These factors, especially when coupled with long-standing pain, may contribute to a cycle of reinforced expectations in which physiological measures are negatively altered at central pain processing levels further propagating the chronic pain experience [25].…”

Nocebo hyperalgesia and the startle response

“…However, previous experience with a treatment or a drug might create learning effects that shape clinical outcomes (Benedetti et al 2011). In the present study, we measured the previous experience of analgesic creams, but the experienced efficacies of previously used analgesic creams and the expected efficacies in the present experiment did not differ significantly between groups.…”

Perceived outcomes of spiritual healing and explanations – A qualitative study on the perspectives of German healers and their clients

“…All these aspects influence how an illness and its possible therapies are understood and dealt with [35,22]. Placebo responses are nowadays better understood and can be connected to neurobiological function [36,37]. According to the so-called placebomentalist model, the placebo effect is mainly an expectation effect showing a linear correlation of the level of expectation and the effect [33].…”