Individuals with chronic pain have the same response to placebo analgesia as healthy controls in terms of magnitude and reproducibility

Enhancing placebo analgesia: Unravelling the powerful interplay of ownership and verbal suggestion

BACKGROUND

Placebo analgesic research demonstrates pain reduction after using a placebo analgesic. Recent studies have documented that sometimes possessing a placebo analgesic induces placebo analgesia. These prior studies used a 'cream' as the stimulus and proposed that the effect is driven by an expectancy of obtaining benefits from the owned analgesic. This paper examines three pivotal components of placebo analgesia: placebo form, ownership and expectancy induced by verbal suggestion. We investigate analgesic expectancy between cream versus oil form of placebo stimulus and systematically isolate the effects of ownership, verbal suggestion and their interaction, comparing with the effect of use, to decipher the dynamics of placebo analgesia.

METHODS

Study 1 (N = 46) evaluated analgesic expectancy between cream and oil. Study 2 (N = 119) exposed participants to a placebo analgesic oil and randomized them into PU (possess and use), PA (possess and anticipate), P (possess-only) or A (anticipate-only) conditions. Pain outcomes were assessed using a cold pressor test. Comparing PA and P conditions assessed the verbal suggestion effect, comparing PA and A conditions evaluated the possession effect, while comparing PU and PA conditions shed light on the use effect.

RESULTS

In Study 1, participants showed comparable analgesic expectancy for cream and oil. In Study 2, both PA and PU groups performed equally well, reporting higher pain threshold, F(3, 115) = 5.14, p = 0.002,η p 2 $$ {\eta}_p^2 $$  = 0.12; and a greater probability of persistent hand submersion than P and A groups, X2(3) = 8.06, p = 0.045.

CONCLUSION

The findings highlight the significance of integrating possession with expectancy to induce placebo analgesia, which has clinical implications.

SIGNIFICANCE

This study delves into the intricate dynamics of placebo analgesia, shedding light on the significant influence of ownership and verbal suggestion. Through a meticulous exploration of the relationship between ownership and expectancy induced by verbal suggestion, we propose novel avenues for enhancing placebo responses. This research has implications for clinical practice and pain management strategies, potentially revolutionizing approaches to pain relief and therapeutic outcomes. Our findings contribute to a paradigm shift in understanding placebo analgesia, emphasizing the pivotal interaction between ownership and verbal suggestion.

The Nocebo Effect

Adverse nocebo responses can cause harm to patients and interfere with treatment adherence and effects in both clinic practice and clinical trials. Nocebo responses refer to negative outcomes to active medical treatments in clinical trials or practice that cannot be explained by the treatment's pharmacologic effects. Negative expectancies and nocebo effects are less known than placebo responses. Nocebo effects can be triggered by verbal suggestions, prior negative experiences, observation of others experiencing negative outcomes, and other contextual and environmental factors. As research advances over the years, mechanistic knowledge is accumulating on the neurobiological mechanisms of nocebo effects. This review summarizes studies on different facets of nocebo effects and responses and discusses clinical implications, ethical considerations, and future directions.

Placebo effects on cutaneous pain and itch: a systematic review and meta-analysis of experimental results and methodology

ABSTRACT

Placebo effects, positive treatment outcomes that go beyond treatment processes, can alter sensations through learning mechanisms. Understanding how methodological factors contribute to the magnitude of placebo effects will help define the mechanisms by which these effects occur. We conducted a systematic review and meta-analysis of experimental placebo studies in cutaneous pain and itch in healthy samples, focused on how differences in methodology contribute to the resulting placebo effect magnitude. We conducted meta-analyses by learning mechanism and sensation, namely, for classical conditioning with verbal suggestion, verbal suggestion alone, and observational learning, separately for pain and itch. We conducted subgroup analyses and meta-regression on the type of sensory stimuli, placebo treatment, number of acquisition and evocation trials, differences in calibrated intensities for placebo and control stimuli during acquisition, age, and sex. We replicated findings showing that a combination of classical conditioning with verbal suggestion induced larger placebo effects on pain ( k = 68, g = 0 . 59) than verbal suggestion alone ( k = 39, g = 0.38) and found a smaller effect for itch with verbal suggestion alone ( k = 7, g = 0.14). Using sham electrodes as placebo treatments corresponded with larger placebo effects on pain than when topical gels were used. Other methodological and demographic factors did not significantly affect placebo magnitudes. Placebo effects on pain and itch reliably occur in experimental settings with varied methods, and conditioning with verbal suggestion produced the strongest effects. Although methods may shape the placebo effect to some extent, these effects appear robust overall, and their underlying learning mechanisms may be harnessed for applications outside the laboratory.

Placebo and nocebo effects: from observation to harnessing and clinical application

Placebo and nocebo effects are salubrious benefits and negative outcomes attributable to non-specific symbolic components. Leveraging advanced experimental and analytical approaches, recent studies have elucidated complicated neural mechanisms that may serve as a solid basis for harnessing the powerful self-healing and self-harming capacities and applying these findings to improve medical practice and minimize the unintended exacerbation of symptoms in medical practice. We review advances in employing psychosocial, pharmacological, and neuromodulation approaches to modulate/harness placebo and nocebo effects. While these approaches show promising potential, translating these research findings into clinical settings still requires careful methodological, technical, and ethical considerations.

The association of affective state with the assimilation of daily pain expectancy and pain experience

ABSTRACT

Expectancies for pain and pain relief are central to experimental models of placebo analgesia and nocebo hyperalgesia, and are a promising target for clinical intervention in patients with chronic pain. Affective states may play an important role in modulating the degree to which expectancies influence pain, broadening the opportunities for intervention targets. However, findings to date have been mixed and mostly limited to laboratory designs. Few studies have examined the interplay of naturally occurring affective states, pain expectancies, and pain experiences in the course of daily life with chronic pain. In the present study, patients with temporomandibular disorder reported their daily pain expectancies and affective states each morning, and their daily pain experience each evening, over a two-week period. Multilevel modeling analyses revealed the association of morning pain expectancies with subsequent pain experiences was moderated by morning positive affective state (B=.04, SE=.02, t=2.00, p=.046), such that the congruent assimilation of a low pain expectancy with a low pain experience was starkest when morning positive affect was higher than usual. Relatedly, higher morning positive affect predicted greater odds of experiencing a match between pain expectancies and pain experience when the expectation was for low, but not high, pain levels (OR: 1.19, CI: 1.01-1.41, p=.03). Negative affect, in contrast, did not significantly influence the assimilation of high pain expectancies with high pain experiences. These findings extend prior experimental studies by showing that the association of daily pain expectancies with pain experience varies as a function of affective state.

ERP Indicators of Self-Pain and Other Pain Reductions due to Placebo Analgesia Responding: The Moderating Role of the Fight-Flight-Freeze System

This study evaluates the modulation of phasic pain and empathy for pain induced by placebo analgesia during pain and empathy for pain tasks. Because pain can be conceptualized as a dangerous stimulus that generates avoidance, we evaluated how approach and avoidance personality traits modulate pain and empathy for pain responses. We induced placebo analgesia to test whether this also reduces self-pain and other pain. Amplitude measures of the N1, P2, and P3 ERPs components, elicited by electric stimulations, were obtained during a painful control, as well as during a placebo treatment expected to induce placebo analgesia. The placebo treatment produced a reduction in pain and unpleasantness perceived, whereas we observed a decrease in the empathy unpleasantness alone during the empathy pain condition. The moderator effects of the fight-flight-freeze system (FFFS) in the relationships linking P2 and P3 amplitude changes with pain reduction were both significant among low to moderate FFFS values. These observations are consistent with the idea that lower FFFS (active avoidance) scores can predict placebo-induced pain reduction. Finally, in line with the revised Reinforcement Sensitivity Theory (r-RST), we can assume that phasic pain is an aversive stimulus activating the active-avoidance behavior to bring the system back to homeostasis.

Prior Pain Exposure and Mere Possession of a Placebo Analgesic Predict Placebo Analgesia: Findings From a Randomized, Double-Blinded, Controlled Trial

A recent study found that merely possessing a placebo analgesic reduces pain. The current study tested for a possible moderator of this effect. Specifically, does the mere possession of a placebo analgesic affect pain for individuals with and without immediate prior experience with the pain task? Healthy participants (N = 127) were randomized to prior pain (PP) condition or without prior pain (No-PP) condition. In the PP condition, participants first did a preliminary trial of a cold pressor test (CPT) to induce direct experience with this pain stimulus. Then they were randomized to possess an inert cream described as either an analgesic cream or an anti-itch cream (pain-irrelevant control object). Participants then completed the main CPT. In the No-PP condition, participants underwent identical procedures and randomization except that they did not do a preliminary CPT, thus having no immediate prior CPT pain experience. We found a significant prior pain experience and possession status interaction effect on placebo analgesia. Participants in the No-PP condition showed evidence of lower pain when they merely possessed an analgesic cream than an anti-itch cream. Such mere possession effect was not found in the PP condition. The impact of expectancy and emotion on the underlying process are discussed. PERSPECTIVE: This article presents a novel finding that prior pain exposure and mere possession of a placebo analgesic predicted placebo analgesia. It offers a novel perspective on the time course of placebo effect. It provides practical implications on potential pain intervention for clinicians and paradigm design for researchers of placebo study.