The Placebo Effect in Pain Therapies

Abstract

Pharmacological strategies for pain management have primarily focused on dampening ascending neurotransmission and on opioid receptor-mediated therapies. Little is known about the contribution of endogenous descending modulatory systems to clinical pain outcomes and why some patients are mildly affected while others suffer debilitating pain-induced dysfunctions. Placebo effects that arise from patients' positive expectancies and the underlying endogenous modulatory mechanisms may in part account for the variability in pain experience and severity, adherence to treatment, distinct coping strategies, and chronicity. Expectancy-induced analgesia and placebo effects in general have emerged as useful models to assess individual endogenous pain modulatory systems. Different systems and mechanisms trigger placebo effects that highly impact pain processing, clinical outcomes, and sense of well-being. This review illustrates critical elements of placebo mechanisms that inform the methodology of clinical trials, the discovery of new therapeutic targets, and the advancement of personalized pain management. Expected final online publication date for the Annual Review of Pharmacology and Toxicology Volume 59 is January 6, 2019. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Modeling Learning Patterns to Predict Placebo Analgesic Effects in Healthy and Chronic Orofacial Pain Participants

“…Placebo analgesia describes the beneficial results of a treatment that are due to context, rather than the actions of a drug (1,3,31). Previous studies have postulated and demonstrated that prior experiences (pain ratings during a conditioning phase), sensory information (intensity of painful stimuli), and context (cues) all contribute to the f o r m a t i o n o f p l a c e b o a n a l g e s i a ( 3 -5 ) .…”

“…Aside from the limitations, the strengths of the current study need to be outlined. First, this is the first study exploring placebo analgesia in chronic orofacial pain (1). Second, this is first study to use LCA modeling of a response pattern during the conditioning phase of a well-controlled experimental setting for placebo analgesia.…”

“…Placebo effects represent a phenomenon that encompasses psychological, biological, and interpersonal aspects of human physiology and behavior (1). A variety of frameworks, theories, and concepts have been postulated in an attempt to understand how placebo effects are elicited, formed, and maintained over time (2).…”

Pressure Release Technique Versus Placebo Applied to Cervical and Masticatory Muscles in Patients With Chronic Painful Myofascial Temporomandibular Disorder. A Randomized Clinical Trial

“…Further studies may look into the long-terms effects of PRT. It would also have been an advantage to include a statement or rating of the expectations and anticipation of treatment effects in the 2 groups because of the strong impact on placebo responses [37]. However, the attempt to include a sham PRT is a signi cant advantage in the interpretation of the present results.…”

Relieving acute pain (RAP) study: a proof-of-concept protocol for a randomised, double-blind, placebo-controlled trial

“…One plausible strategy to fight against the opioid epidemic is to include placebos with analgesics for pain management 12 13. Extensive research on placebo analgesia over the past several decades has expanded knowledge of a fascinating psycho-neurobiological phenomenon underlying endogenous pain reduction 14 15. This provocative line of research involves the use of placebos to enhance therapeutic outcomes through learning paradigms that produce behavioural and biological responses mirroring those induced by active drugs.…”