An analysis of factors that contribute to the magnitude of placebo analgesia in an experimental paradigm

Hypnosis Associated with 3D Immersive Virtual Reality Technology in the Management of Pain: A Review of the Literature

Hypnosis is well documented in the literature in the management of acute and chronic pain. Virtual reality (VR) is currently gaining credibility in the same fields as hypnosis for medical applications. Lately, the combination of hypnosis and VR was considered. The aim of this scoping review is to understand the current studied contexts and effects of virtual reality hypnosis (VRH) for the management of pain. We searched on PubMed, Taylor & Francis Online, and ProQuest databases with the following terms: “virtual reality,” “3D,” “hypnosis,” and “pain”. We included 8 studies that combined hypnosis and VR. All articles are in English. Two included healthy volunteers and six are clinical studies. Short-term results indicated significant decreases in pain intensity, pain unpleasantness, time spent thinking about pain, anxiety, and levels of opioids. However, results are not consistent for all patients all the days. VR alone seems to reduce pain independently of the hypnotizability level. One study claimed that VR and hypnosis could alter each other’s effects and another argued that VR did not inhibit the hypnotic process and may even facilitate it by employing visual imagery. We cannot affirm that VR added value to hypnosis when they are combined. These trials and case series gave us indications about the possible applications of VRH in different contexts. Additional randomized clinical trials on VRH in the future will have to test this technique in clinical practice and help define guidelines for VRH utilization in pain management.

Can we harness the placebo effect to improve care in lower urinary tract dysfunction? ICI-RS 2019

The proposal "Can we harness the placebo effect to improve care in lower urinary tract dysfunction?" was discussed at the International Consultation on Incontinence-Research Society (ICI-RS) 2019 meeting. The placebo effect can change the treatment outcome whether the treatment is an active treatment or placebo. The total active treatment outcome is a combination of the placebo and the active treatment effect which is seen in placebo-controlled trials. The placebo effect plays an important role in the treatment of lower urinary tract dysfunction in overactive bladder, bladder pain syndrome, and stress urinary incontinence. In clinical practice, a number of factors can be employed to use the placebo effect to maximize its effect on patients receiving an active treatment, such as having the same environment for review such as the same appointment time, same room, and same clinician. Clinicians should also be aware of the nocebo effect which is increased with an overemphasis on side effects or negative outcomes.

Expectancy and Utilisation of Reflexology among Women with Advanced Breast Cancer

OBJECTIVE

Little is understood about patient expectations and use of complementary therapies (CT) during cancer treatment. A secondary analysis of an 11-week reflexology trial among women with breast cancer was conducted. We examined factors that predicted women's expectations about reflexology for symptom relief, factors that predicted utilisation of reflexology, and whether by the end of the trial they believed that reflexology had helped with symptom management.

METHODS

Women (N = 256) were interviewed at baseline and week 11. Friend or family caregivers in the reflexology group were trained to deliver standardised sessions to patients at least once a week for 4 weeks. Baseline and week-11 reflexology expectations were analysed using general linear models. Reflexology utilisation was analysed with generalised linear mixed effects models.

RESULTS

Patients who expected benefits from reflexology ("higher expectancy") at baseline were younger, had lower anxiety, higher education, higher spirituality, and greater CT use. Worsening symptoms over time were associated with greater utilisation of reflexology, but only when baseline expectancy was low. At week 11, expectancy was higher for those with greater symptom improvement.

CONCLUSIONS

Assessing patterns of patient factors, expectancy, and change in symptoms can help determine who is likely to use reflexology, and when.

Choice, Expectations, and the Placebo Effect for Sleep Difficulty

BACKGROUND

Choice has been found to facilitate placebo effects for single-session treatments where standard placebo treatment without choice failed to elicit a placebo effect. However, it is unknown whether choice can enhance the placebo effect for treatments occurring over a period of days and where placebo effects are readily established without choice.

PURPOSE

We tested whether single or daily choice between two (placebo) treatments enhanced the placebo effect for sleep difficulty relative to no choice and no treatment over a 1 week period.

METHODS

One-hundred and seventeen volunteers self-identifying with sleep difficulty were recruited under the guise of a hypnotic trial and randomized to one of the four groups. Self-reported outcomes included insomnia severity, fatigue, total sleep time (TST), sleep onset latency (SOL), perceived sleep quality (PSQ), and treatment satisfaction. Objective TST and SOL were assessed in a subsample via actigraphy.

RESULTS

Overall, placebo treatment significantly improved insomnia severity, fatigue, and PSQ, confirming a placebo effect on these outcomes. However, both traditional and Bayesian analysis indicated no benefit of choice on the placebo effect on any sleep outcome. Mediation analysis of the overall placebo effect indicated that expectancy completely mediated the placebo effects for insomnia severity and PSQ and partially mediated the placebo effect for fatigue.

CONCLUSION

These findings suggest that choice does not enhance the placebo effect over longer treatment periods (up to 7 days) when placebo effects are readily established without choice. As such, any benefit of choice on placebo effects may be confined to quite specific circumstances.

CLINICAL TRIALS REGISTRATION

ACTRN12618001199202.

An Exploration of Knowledge and Attitudes of Medical Students and Rheumatologists to Placebo and Nocebo Effects: Threshold Concepts in Clinical Practice

INTRODUCTION

Understanding placebo and nocebo responses (context/meaning effects [CMEs]) is fundamental to physician agency. Specific instruction in CMEs is often lacking in medical education. Patient-practitioner interactions may challenge medical students' understanding of biomedical causality and the nexus between this, practical ethics and professionalism across various conceptual and applied aspects of CMEs. This study compared the corpus of knowledge and phronesis related to CMEs between Australian graduate medical students and rheumatologists to gain a sophisticated understanding of this relationship to inform curriculum development.

METHOD

In 2013 and 2014, the authors surveyed third-year medical students undertaking a graduate programme in an Australian medical school and Australian rheumatologists to ascertain their understanding of placebo and nocebo responses. The survey ascertained (1) the alignment of the respondents' understanding of CMEs with accepted facts and concepts; (2) opinions on the ethical status of CMEs; and (3) responses to 2 scenarios designed to explore matters of biomedical causality, practical ethics and professionalism.

RESULTS

There were 88 completed surveys returned, 53 rheumatologists and 35 students. Similar proportions within each group identified CMEs, with most (n = 79/88 [89.8%]) correctly recognising a placebo (rheumatologists: 50 [94.3%], students: 29 [82.9%]) and approximately three-quarters (n = 65/88 [73.9%]) correctly recognising nocebo effects (rheumatologists: 39 [73.6%], students: 26 [74.3%]). Statistically significant differences between practitioners and students were observed in relation to the following: placebo responders and placebo responsiveness; placebos as a 'diagnostic tool'; placebos usage in clinical practice and research, and nocebo effects.

CONCLUSIONS

Physicians require an awareness of CMEs and the fact that they arise from and influence the effective agency of health care professionals. Curricular emphasis is needed to permit an honest assessment of the components that influence when, how and why patient outcomes arise, and how one's agency might have neutral or negative effects but could be inclined towards positive and away from negative patient outcomes.

The Context of Values in Pain Control: Understanding the Price Effect in Placebo Analgesia

The experience of pain relief arises from physiological and psychological factors, and attributes such as the commercial features of analgesic treatments have been shown to influence placebo analgesia by affecting treatment expectations. Therefore, treatment valuation from price information should influence the placebo analgesic effect. This hypothesis was tested in a functional magnetic resonance imaging study in which healthy subjects were enrolled in a 2-day experiment. On day 1, the participants (n = 19) had treatment experiences with 2 different placebo creams during a conditioning session without receiving information on treatment price. On day 2, placebo analgesia was tested after providing price information (high vs low) while functional magnetic resonance imaging was performed. The results showed that the higher priced placebo treatment leads to enhanced pain relief. Placebo analgesia in response to the higher priced treatment was associated with activity in the ventral striatum, ventromedial prefrontal cortex, and ventral tegmental area. The behavioral results indicate that the experience of pain was influenced by treatment valuation from price. Our findings reveal that the context of values in pain control is associated with activity in expectation- and reward-related circuitry. PERSPECTIVE: Treatment with higher price was associated with enhanced placebo analgesia, and this effect was influenced by activities in expectation and reward processing brain areas. The context of value such as medical cost influences cognitive evaluation processes to modulate pain. Our study may help evaluate a patient's preference toward high-priced drugs.

Placebo trials without mechanisms: How far can they go?

In this paper, I suggest that placebo effects, as we know them today, should be understood as experimental phenomena, low-level regularities whose causal structure is grasped through particular experimental designs with little theoretical guidance. Focusing on placebo interventions with needles for pain reduction -one of the few placebo regularities that seems to arise in meta-analytical studies- I discuss the extent to which it is possible to decompose the different factors at play through more fine-grained randomized clinical trials. My sceptical argument is twofold. On the one hand, I argue that experiments alone are not enough to standardize interventions, and that it is necessary to include theories. On the other hand, I argue that the social interactions that seem to be part of placebo effects are difficult, if not impossible, to blind. Therefore, the measurement biases arising from the participants' reactivity to the experimental setup cannot be controlled for. Further decomposition of placebo effects requires a theoretical account of the existing experimental regularities that may guide further tests.

Placebo analgesia induced by verbal suggestion in the context of experimentally induced fear and anxiety

The role of state anxiety and state fear in placebo effects is still to be determined. We aimed to investigate the effect of fear of movement-related pain (FMRP) and contextual pain related anxiety (CPRA) on the magnitude of placebo analgesia induced by verbal suggestion. Fifty-six female participants completed a modified voluntary joystick movement paradigm (VJMP) where half participated in a predictable pain condition (PC), in which one of the joystick movements is always followed by pain and the other movement is never followed by pain, and half in an unpredictable pain condition (UC), in which pain was delivered unpredictably. By varying the level of pain predictability, FMRP and CPRA were induced in PC and UC respectively. Colour stimuli were presented at the beginning of each trail. Half of the participants were verbally informed that the green or red colour indicated less painful stimuli (experimental groups), the other half did not receive any suggestion (control groups). We measured self-reported pain intensity, expectancy of pain intensity (PC only), pain related fear and anxiety (eyeblink startle response and self-ratings) and avoidance behaviour (movement-onset latency and duration). The results indicate that the placebo effect was successfully induced in both experimental conditions. In the PC, the placebo effect was predicted by expectancy. Despite the fact that FMRP and CPRA were successfully induced, no difference was found in the magnitude of the placebo effect between PC and UC. Concluding, we did not find a divergent effect of fear and anxiety on placebo analgesia.

Evaluating the Effects of Acupuncture Using a Dental Pain Model in Healthy Subjects - A Randomized, Cross-Over Trial

Acupuncture is a complementary and nonpharmacological intervention that can be effective for the management of chronic pain in addition to or instead of medication. Various animal models for neuropathic pain, inflammatory pain, cancer-related pain, and visceral pain already exist in acupuncture research. We used a newly validated human pain model and examined whether acupuncture can influence experimentally induced dental pain. For this study, we compared the impact of manual acupuncture (real acupuncture), manual stimulation of a needle inserted at nonacupuncture points (sham acupuncture) and no acupuncture on experimentally induced dental pain in 35 healthy men who were randomized to different sequences of all 3 interventions in a within-subject design. BORG CR10 pain ratings and autonomic responses (electrodermal activity and heart rate variability) were investigated. An initial mixed model with repeated measures included preintervention pain ratings and the trial sequence as covariates. The results showed that acupuncture was effective in reducing pain intensity when compared to no acupuncture (β = -.708, P = .002), corresponding to a medium Cohen's d effect size of .56. The comparison to the sham acupuncture revealed no statistically significant difference. No differences in autonomic responses between real and sham acupuncture were found during the intervention procedures. PERSPECTIVE: This study established a dental pain model for acupuncture research and provided evidence that experimentally induced dental pain can be influenced by either real acupuncture or manual stimulation of needles at nonacupuncture points. The data do not support that acupoint specificity is a significant factor in reducing experimental pain.

Anterior cingulate and medial prefrontal cortex response to systematically controlled tonal dissonance during passive music listening

Several studies have attempted to investigate how the brain codes emotional value when processing music of contrasting levels of dissonance; however, the lack of control over specific musical structural characteristics (i.e., dynamics, rhythm, melodic contour or instrumental timbre), which are known to affect perceived dissonance, rendered results difficult to interpret. To account for this, we used functional imaging with an optimized control of the musical structure to obtain a finer characterization of brain activity in response to tonal dissonance. Behavioral findings supported previous evidence for an association between increased dissonance and negative emotion. Results further demonstrated that the manipulation of tonal dissonance through systematically controlled changes in interval content elicited contrasting valence ratings but no significant effects on either arousal or potency. Neuroscientific findings showed an engagement of the left medial prefrontal cortex (mPFC) and the left rostral anterior cingulate cortex (ACC) while participants listened to dissonant compared to consonant music, converging with studies that have proposed a core role of these regions during conflict monitoring (detection and resolution), and in the appraisal of negative emotion and fear‐related information. Both the left and right primary auditory cortices showed stronger functional connectivity with the ACC during the dissonant portion of the task, implying a demand for greater information integration when processing negatively valenced musical stimuli. This study demonstrated that the systematic control of musical dissonance could be applied to isolate valence from the arousal dimension, facilitating a novel access to the neural representation of negative emotion.

Memory of pain in adults: a protocol for systematic review and meta-analysis

BACKGROUND

The way pain is remembered and reported can affect medical decisions taken by patients and health-care professionals. Memory of pain has been investigated extensively for the past few decades; however, the results of previous studies are highly variable, indicating that the recollection of pain can be accurate, overestimated or underestimated. It is therefore difficult to conclude how well pain is remembered. The aim of this systematic review and meta-analysis is to summarize research findings on memory of pain in healthy adults and patients suffering from acute and chronic pain.

METHODS

The systematic review will be performed by searching for articles indexed in the following databases: PubMed, MEDLINE, PsycINFO, Web of Science, ScienceDirect, PsycARTICLES, Scopus and Academic Search Complete. Studies will be included if (1) they investigated healthy adults or patients with any acute or chronic pain condition and if (2) they assessed experienced pain (pain intensity and/or pain unpleasantness) and its recollection. No restrictions related to the date of publication and recall delay will be applied. Studies will be screened for eligibility and risk of bias by two independent assessors. The risk of bias will be assessed by a modified Downs and Black checklist. A narrative synthesis will be performed in the first stage; in the second stage, the results of studies with comparable designs will be pooled in meta-analytical syntheses.

DISCUSSION

The question of whether pain is remembered accurately is crucial for valid pain diagnosis, effective treatment and prognosis. So far, a number of studies on memory of pain have been conducted; however, a definitive conclusion on whether memory of pain is accurate is still lacking. In this systematic review and meta-analysis, available data will be pooled together to further inform research and clinical practice.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42018093523.

Endogenous cortisol and conditioned placebo effects on pain - A randomized trial

Placebo effects can be induced by learning and conditioning processes, which in turn are influenced and modulated by glucocorticoids. Accordingly, previous research has shown that intervention-related associative learning can be modulated through exogenous as well as endogenous glucocorticoids. Thus, the aim of this study was to elucidate whether placebo effects induced by conditioning is modulated by daily fluctuations of endogenous cortisol levels in healthy male and female subjects. Overall 77 participants underwent a two-phased placebo conditioning paradigm for pain analgesia. Subjects were randomized in two groups, which underwent placebo preconditioning either in the morning (08:00-10:00, i.e. with high endogenous cortisol levels) or in the afternoon (16:00-18:00, i.e. with low endogenous cortisol levels). Placebo effects were assessed two days later at noontime (12:00-13:00), with possible differences between groups as an indicator of glucocorticoid modulation on the placebo learning. Results indicated a significant conditioned placebo-induced analgesia, resulting in a placebo effect of small to medium size. Cortisol levels on conditioning day significantly differed between groups and cortisol levels were similar during assessment of placebo effects. Groups did not differ in their mean reduction in pain sensation, thus the placebo effect was not affected by differences in cortisol levels during the conditioning of placebo effects. The present study does not indicate a moderation of placebo conditioning by endogenous glucocorticoid levels.

When words hurt: Verbal suggestion prevails over conditioning in inducing the motor nocebo effect

Perception and behavior are strongly influenced by the verbal information conveyed by other individuals (e.g., verbal suggestion) and by learning (e.g., conditioning). This influence is well represented by the placebo and nocebo effects, in which positive verbal suggestion associated with positive conditioning induces beneficial outcomes (placebo effect), while the opposite is true for the negative counterpart (nocebo effect). It is still unclear whether verbal suggestion and conditioning exert distinctive roles in influencing perception, behavior and motor system activity when they occur in opposite directions. To this purpose, fifty-three healthy volunteers were assigned to four groups characterized by either congruent or incongruent verbal suggestion and conditioning. Participants were asked to perform a force motor task by pressing a piston as strongly as possible. Transcranial magnetic stimulation over the primary motor cortex was used to record motor evoked potentials (MEP) and cortical silent period (CSP) from the muscle involved in the task. We found that negative verbal suggestion counteracted positive conditioning and induced sense of weakness, effort, and force decrements. MEP amplitude was stable, whereas the CSP duration shortened in all the groups throughout the procedure, indicating the involvement of cortical inhibitory circuits, independently of the type of verbal suggestion or conditioning. Our findings highlight a prevalent role of verbal suggestion over conditioning in determining a worsening (nocebo effect) but not an improvement (placebo effect) of motor performance. These results suggest that words associated with treatments should be chosen carefully to avoid negative outcomes, especially in sports and clinical settings.

When Your Doctor "Gets It" and "Gets You": The Critical Role of Competence and Warmth in the Patient-Provider Interaction

Background: Research demonstrates that the placebo effect can influence the effectiveness of medical treatments and accounts for a significant proportion of healing in many conditions. However, providers may differ in the degree to which they consciously or unconsciously leverage the forces that produce placebo effects in clinical practice. Some studies suggest that the manner in which providers interact with patients shapes the magnitude of placebo effects, but this research has yet to distill the specific dimensions of patient-provider interactions that are most likely to influence placebo response and the mechanisms through which aspects of patient-provider interactions impact placebo response. Methods: We offer a simplifying and unifying framework in which interactions that boost placebo response can be dissected into two key dimensions: patients' perceptions of competence, or whether a doctor "gets it" (i.e., displays of efficiency, knowledge, and skill), and patients' perceptions of warmth, or whether a doctor "gets me" (i.e., displays of personal engagement, connection, and care for the patient). Results: First, we discuss how this framework builds on past research in psychology on social perception of competence and warmth and in medical literature on models of effective medical care, patient satisfaction, and patient-provider interactions. Then we consider possible mechanisms through which competence and warmth may affect the placebo response in healthcare. Finally, we share original data from patients and providers highlighting how this framework applies to healthcare. Both patient and provider data illustrate actionable ways providers can demonstrate competence and warmth to patients. Discussion: We conclude with recommendations for how researchers and practitioners alike can more systematically consider the role of provider competence and warmth in patient-provider interactions to deepen our understanding of placebo effects and, ultimately, enable providers to boost placebo effects alongside active medications (i.e., with known medical ingredients) and treatment in clinical care.

Reinterpreting homoeopathy in the light of placebo effects to manage patients who seek homoeopathic care: A systematic review

Homoeopathy is widespread, and users claim to benefit from it. However, clear evidence of its efficacy over placebo is not available to date. As a consequence, a social separation between homoeopathy users and mainstream medicine exists, exposing these patients to many risks. Our primary objective is to assess homoeopathy efficacy by systematically reviewing existing systematic reviews and meta-analyses and to systematically review trials on open-label placebo (OLP) treatments. A secondary objective is to understand if homoeopathy as a whole may be considered as a placebo treatment. PubMed/Medline, Embase, Google Scholar, and Cochrane Library were systematically searched for systematic reviews and meta-analyses on homoeopathy efficacy, and 61 studies were included. Same databases plus Journal of Interdisciplinary Placebo Studies (JIPS) were also systematically searched for randomised controlled trials (RCTs) on OLP treatments, and 10 studies were included. Databases were searched up to 24 February 2018. Two authors independently screened all retrieved articles and selected studies eligible for inclusion. The quality of reviews of included studies was evaluated with a dedicated NIH tool in the first review, whereas the risk of bias of trials of included studies was assessed with the specific Cochrane tool in the second review. Qualitative syntheses show that homoeopathy efficacy can be considered comparable to placebo, and that OLP treatments may be effective in some health conditions. Placebo effects like placebo itself, treatment context, physician-patient relationship, and other nonspecific factors can define the idea of placebo treatments, which may be effective in some conditions. If homoeopathy efficacy is comparable to placebo, and if placebo treatments can be effective in some conditions, then homoeopathy as a whole may be considered as a placebo treatment. Reinterpreting homoeopathy as a placebo treatment would define limits and possibilities of this practice. This perspective shift suggests a strategy to manage patients who seek homoeopathic care and to reconcile them with mainstream medicine in a sustainable way.

Classical Conditioning as a Distinct Mechanism of Placebo Effects

Classical conditioning was suggested as a mechanism of placebo effects in the 1950s. It was then challenged by response expectancy theory, which proposed that classical conditioning is just one of the means by which expectancies are acquired and changed. According to that account, placebo effects induced by classical conditioning are mediated by expectancies. However, in most of the previous studies, either expectancies were not measured or classical conditioning was combined with verbal suggestions. Thus, on the basis of those studies, it is not possible to conclude whether expectancies are involved in placebo effects induced by pure classical conditioning. Two lines of recent studies have challenged the idea that placebo effects induced by classical conditioning are always mediated by expectancies. First, some recent studies have shown that a hidden conditioning procedure elicits both placebo analgesia and nocebo hyperalgesia, neither of which is predicted by expectancy. Second, there are studies showing that visual cues paired with pain stimuli of high or low intensity induce both placebo analgesia and nocebo hyperalgesia when they are presented subliminally without participants' awareness. The results of both lines of studies suggest that expectancy may not always be involved in placebo effects induced by classical conditioning and that conditioning may be a distinct mechanism of placebo effects. Thus, these results support the idea that placebo effects can be learned by classical conditioning either consciously or unconsciously. However, the existing body of evidence is limited to classically conditioned placebo effects in pain, that is, placebo analgesia and nocebo hyperalgesia.

It is not just the drugs that matter: the nocebo effect

The role of psychological mechanisms in the treatment process cannot be underestimated, the well-known placebo effect unquestionably being a factor in treatment. However, there is also a dark side to the impact of mental processes on health/illness as exemplified by the nocebo effect. This phenomenon includes the emergence or exacerbation of negative symptoms associated with the therapy, but arising as a result of the patient's expectations, rather than being an actual complication of treatment. The exact biological mechanisms of this process are not known, but cholecystokinergic and dopaminergic systems, changes in the HPA axis, and the endogenous secretion of opioids are thought to be involved. The nocebo effect can affect a significant proportion of people undergoing treatment, including cancer patients, leading in some cases to the cessation of potentially effective therapy, because of adverse effects that are not actually part of the biological effect of treatment. In extreme cases, as a result of suggestions and expectations, a paradoxical effect, biologically opposite to the mechanism of the action of the drug, may occur. In addition, the nocebo effect may significantly interfere with the results of clinical trials, being the cause of a significant proportion of complications reported. Knowledge of the phenomenon is thus necessary in order to facilitate its minimalization and thus improve the quality of life of patients and the effectiveness of treatment.

Placebo analgesia effects across central nervous system diseases: what do we know and where do we need to go?

Placebo effects are well established in healthy participants experiencing experimental or acute pain. Yet, little is known about the mechanisms of placebo analgesia effects in patients with chronic pain and even less is known in patients suffering from central nervous system (CNS) diseases where pain is prevalent, difficult to manage, and often undertreated. This article briefly reviews the current knowledge of placebo analgesia effects in healthy participants with the aim of discussing how the mechanisms in placebo analgesia differ between healthy participants and patients. The focus will be on placebo analgesia effects in chronic pain conditions as well as in 2 CNS diseases: Alzheimer disease and Parkinson disease. Finally, strengths and weaknesses of the current knowledge will be discussed and it will be demonstrated how insights from the placebo literature may point to new ways of improving treatments among patients experiencing pain in relation to CNS diseases.

Study protocol for a randomised, double-blind, placebo-controlled clinical trial of duloxetine for the treatment and prevention of musculoskeletal pain: altering the transition from acute to chronic pain (ATTAC pain)

INTRODUCTION

Chronic musculoskeletal pain affects a substantial portion of adults visiting the emergency department (ED). Current treatment is limited in scope and does not effectively reduce musculoskeletal pain in patients. The study will evaluate the use of duloxetine, a serotonin-norepinephrine reuptake inhibitor Food and Drug Administration approved for the treatment of chronic pain, as a promising option in its prevention. The proposed study may present a well-tolerated and effective non-opioid treatment for patients with acute musculoskeletal pain that may also be effective in preventing the transition to persistent or chronic musculoskeletal pain.

METHODS AND ANALYSIS

The primary outcome of this study will be to assess the tolerability and preliminary effectiveness of duloxetine in patients with acute musculoskeletal pain. The study will take place at two EDs in Rhode Island, USA. The study will involve randomisation to one of three arms: duloxetine 30 mg, duloxetine 60 mg or placebo. Tolerability will be assessed by comparing the proportion of participants that report an adverse event and that drop-out across the three study arms. Effectiveness will be determined by self-reported pain over 6 weeks of follow-up. Specifically, we will compare the proportion of participants with persistent pain (ongoing pain at 6-week follow-up), across the three study arms. 60 adults (aged 18-59) presenting to the ED with acute axial musculoskeletal pain within 7 days of onset are expected to be enrolled in the proposed study.

ETHICS AND DISSEMINATION

Ethics approval was obtained by the Institutional Review Board (IRB). These results will be published in a peer reviewed scientific journal and presented at one or more scientific conferences.

TRIAL REGISTRATION NUMBER

NCT03315533.

The Influence of Expectancy Level and Personal Characteristics on Placebo Effects: Psychological Underpinnings

Placebo effects benefit a wide range of clinical practice, which can be profoundly influenced by expectancy level and personal characteristics. However, research on the issue of whether these factors independently or interdependently affect the placebo effects is still in its infancy. Here, we adopted a 3-day between-subject placebo analgesia paradigm (2-day conditioning and 1-day test) to investigate the influence of expectancy levels (i.e., No, Low, and High) and personal characteristics (i.e., gender, dispositional optimism, and anxiety state) on placebo effects in 120 healthy participants (60 females). Our results showed that the reduction of pain intensity in the test phase was influenced by the interaction between expectancy and gender, as mainly reflected by greater reductions of pain intensity in females at Low expectancy level than females at No/High expectancy levels, and greater reductions of pain intensity in males than in females at High expectancy level. Additionally, the reduction of pain unpleasantness was not only modulated by the interaction between expectancy and gender, but also by the interaction between expectancy and dispositional optimism, as well as the interaction between expectancy and anxiety state. Specifically, participants who were more optimistic in Low expectancy group, or those who were less anxious in High expectancy group showed greater reductions of pain unpleasantness. To sum up, we emphasized on regulating the expectancy level individually based on the assessment of personal characteristics to maximize placebo effects in clinical conditions.

Open-label placebo response - Does optimism matter? A secondary-analysis of a randomized controlled trial

OBJECTIVE

Open-label placebos (OLPs) have been found to elicit significant and clinical meaningful effects, but in comparison to deceptive placebo administration there is a lack of research regarding possible predictors. This study sets out to examine the effects of optimism and other personality-related variables on OLP responses.

METHODS

We conducted a secondary-analysis of an OLP trial in healthy participants (N = 160), who were randomized to no treatment (NT), OLP without rationale (OPR^-), OLP with rationale (OPR⁺), and deceptive placebo (DP) in an experimental heat pain paradigm.

RESULTS

The association between objective posttreatment pain tolerance and optimism did not differ among groups. However, for subjective heat pain ratings at posttreatment, regression analyses showed a significant interaction between group and optimism scores in subjective intensity (F[3, 142] = 3.81, P = 0.012) and unpleasantness ratings (F[3, 142] = 2.95, P = 0.035), indicating that the association between optimism and subjective ratings differed among groups, in particular between OPR⁺ and NT (intensity: P = 0.012; unpleasantness: P = 0.037), and OPR⁺ and DP (intensity: P = 0.016). Thus, higher optimism scores were negatively associated with subjective ratings in the NT and DP groups but not in the OPR⁺ group. Additional exploratory analyses revealed no significant interactions between group and further personality-related variables on heat pain analgesia.

CONCLUSION

Taken together, OLPs are effective, the underlying personality-related variables seem, however, to differ significantly from the deceptive placebo response. Therefore, the concept of "placebo responders" might depend on the route of placebo administration.

A neural mechanism of direct and observational conditioning for placebo and nocebo responses

Classical theories suggest placebo analgesia and nocebo hyperalgesia are based on expectation and conditioned experience. Whereas the neural mechanism of how expectation modulates placebo and nocebo effects during pain anticipation have been extensively studied, little is known about how experience may change brain networks to produce placebo and nocebo responses. We investigated the neural pathways of direct and observational conditioning for conscious and nonconscious conditioned placebo/nocebo effects using magnetoencephalography and a face visual cue conditioning model. We found that both direct and observational conditioning produced conscious conditioned placebo and nocebo effects and a nonconscious conditioned nocebo effect. Alpha band brain connectivity changes before and after conditioning could predict the magnitude of conditioned placebo and nocebo effects. Particularly, the connectivity between the rostral anterior cingulate cortex and middle temporal gyrus was an important indicator for the manipulation of placebo and nocebo effects. Our study suggests that conditioning can mediate our pain experience by encoding experience and modulating brain networks.

Clinical Use of Placebo Effects in Patients With Pain Disorders

The analgesic placebo effect is well documented by numerous studies. Many important influencing factors, however, are yet to be discovered. In the arena of placebo effects and clinical implications, expectancies play a central role. Expectancies are shaped by processes of classical and social learning as well as verbal instructions and are strongly related to emotional factors. Expectancies trigger a cascade of endogenous opioids and non-opioids, which alter the experience of pain. For clinical application it is important to know, that placebo research yields ethical possibilities to use placebo effects without deception and without using placebos. Since placebo effects contribute to responses to active analgesics, it is feasible to enhance patients' benefits from pain treatments by increasing the additional placebo effect. There are several possibilities to use the placebo effects via shaping and adapting information about analgesic medication and via associating medication intake with a positive context. A positive patient-clinician communication atmosphere is very important to generate clinically meaningful placebo effects in pain medicine.

Is the rationale more important than deception? A randomized controlled trial of open-label placebo analgesia

Research on open-label placebos questions whether deception is a necessary characteristic of placebo effects. Yet, comparisons between open-label and deceptive placebos (DPs) are lacking. We therefore assessed effects of open-label placebos and DPs in comparison with no treatment (NT) with a standardized experimental heat pain paradigm in a randomized controlled trial in healthy participants. Participants (N = 160) were randomly assigned to NT, open-label placebo without rationale (OPR-), open-label placebo with rationale (OPR), and DP. We conducted baseline and posttreatment measurements of heat pain threshold and tolerance. Apart from the NT, all groups received an application of a placebo cream. Primary outcomes were planned comparisons of heat pain tolerance and the corresponding intensity and unpleasantness ratings. Objective posttreatment pain tolerance did not differ among groups. However, for subjective heat pain ratings at the posttreatment tolerance level, groups with a rationale (OPR and DP) reported diminished heat pain intensity (t(146) = -2.15, P = 0.033, d = 0.43) and unpleasantness ratings (t(146) = -2.43, P = 0.016, d = 0.49) compared with the OPR-group. Interestingly, the OPR and the DP groups did not significantly differ in heat pain intensity (t(146) = -1.10, P = 0.272) or unpleasantness ratings (t(146) = -0.05, P = 0.961) at the posttreatment tolerance level. Our findings reveal that placebos with a plausible rationale are more effective than without a rationale. Even more, open-label placebos did not significantly differ in their effects from DPs. Therefore, we question the ubiquitously assumed necessity of concealment in placebo administration.

Placebo analgesia persists during sleep: An experimental study

Although placebo analgesia is a well-recognized phenomenon with important clinical implications, the possibility that placebo effects occur during sleep has received little attention. This experimental study examined whether responsiveness to acute heat pain stimuli applied during sleep could be reduced following a placebo conditioning procedure administered before sleep. Healthy individuals (n = 9) underwent polysomnographic recordings for one habituation night followed by one placebo analgesia night and one control night in counterbalanced order. Conditioning induced robust analgesia expectations before the placebo night. In the morning after the placebo night, participants reported less nocturnal pain, anxiety, and associated sleep disturbance (all p's < 0.05) compared to the control night. Furthermore, placebo induction produced a 10% reduction in brain arousals evoked by noxious stimuli during rapid-eye-movement (REM) sleep (p = 0.03), consistent with our previous findings suggesting that analgesia expectations are reprocessed during REM sleep. In contrast, arousals increased by 14% during slow wave sleep (SWS) (p = 0.02). In the morning after the last recording night, placebo testing administered as a manipulation check confirmed that typical placebo analgesic responses were produced during waking (p's < 0.05). These results suggest that analgesia expectations developed before sleep reduced nocturnal pain perception and subjective sleep disturbances and activated brain processes that modulate incoming nociceptive signals differentially according to sleep stage. These results need to be replicated in future studies exploring how analgesia expectations may be reactivated during different sleep stages to modulate nociceptive responses.

What's in a word? How instructions, suggestions, and social information change pain and emotion

Instructions, suggestions, and other types of social information can have powerful effects on pain and emotion. Prominent examples include observational learning, social influence, placebo, and hypnosis. These different phenomena and their underlying brain mechanisms have been studied in partially separate literatures, which we discuss, compare, and integrate in this review. Converging findings from these literatures suggest that (1) instructions and social information affect brain systems associated with the generation of pain and emotion, and with reinforcement learning, and that (2) these changes are mediated by alterations in prefrontal systems responsible for top-down control and the generation of affective meaning. We argue that changes in expectation and appraisal, a process of assessing personal meaning and implications for wellbeing, are two potential key mediators of the effects of instructions and social information on affective experience. Finally, we propose a tentative model of how prefrontal regions, especially dorsolateral and ventromedial prefrontal cortex may regulate affective processing based on instructions and socially transmitted expectations more broadly.

Placebo effects of a sham opioid solution: a randomized controlled study in patients with chronic low back pain

This study tested the experimental placebo effect in a group of chronic pain patients. Forty-eight patients having chronic back pain participated in a randomized clinical trial that tested the efficacy of a sham opioid solution (NaCl) compared with an alleged neutral, completely inactive solution (NaCl). We shaped the placebo effect by 2 interventions: verbal instruction and conditioning. The patients were either told that the "solution reduces pain and improves physical capacity" or the "solution is neutral, a placebo." Half of each group was additionally conditioned (coupling solution with reduced experimental pain), yielding 4 subgroups with 12 participants each. Outcome measures were as follows: the patients' clinical back pain ratings and acute pain ratings (both examined by numerical rating scale 0-10) and self-rated functional capacity (0%-100%; time required for the exercise). Expected pain relief before and after solution intake was also assessed. The inactive solution (NaCl), when presented as an effective treatment (sham "opioid" solution), induced placebo analgesia as evident in lower ratings of the patients' clinical back pain (F(3.12,144.21) = 25.05, P < 0.001), acute pain ratings (F(1.99,87.40) = 18.12, P < 0.01), and time needed to complete a series of daily activities exercises (F(1,44) = 8.51, P < 0.01) as well as increased functional capacity (F(1,44.00) = 19.42, P < 0.001). The 2 manipulations (instruction and conditioning) changed pain expectations, and they were maintained in both sham opioid groups. The results suggest that it may be clinically useful to explicitly integrate placebo analgesia responses into pain management.

Placebo response in neuropathic pain after spinal cord injury: a meta-analysis of individual participant data

Background

Understanding factors associated with high placebo responses in clinical trials increases the likelihood of detecting a meaningful treatment effect. The aim of the present study was to identify subject-level factors that contribute to placebo variability in patients with neuropathic pain due to spinal cord injury (SCI).

Methods

Multiple regression analysis of patient data from randomized, double-blind, placebo-controlled trials (duration >4 weeks) involving individuals with SCI was performed. Patient demographics, as well as injury and pain characteristics were examined for their association with changes in pain rating from baseline to the end of the trial (i.e., placebo response). The overall effect of individual predictors was quantified with meta-analysis statistics.

Results

A total of 276 patients with SCI from six studies were included in the analysis. Based on the meta-analysis of subject-level predictors, larger placebo responses were associated with male subjects (β=0.635; standard error [SE]=0.262; p=0.016) and higher baseline pain (β=−0.146; SE=0.073; p=0.044). There were no significant effects for injury characteristics (i.e., severity, level, and time since injury) or pain characteristics (i.e., location and evoked). No significant publication bias was detected.

Conclusion

The current meta-analysis of individual patient data demonstrated the importance of sex and baseline pain intensity on changes in pain ratings in the placebo arm of SCI central neuropathic pain randomized controlled clinical trials. Overall, our findings indicate that placebo responses occur independent of injury characteristics.

The effects of breaks on low back pain, discomfort, and work productivity in office workers: A systematic review of randomized and non-randomized controlled trials

The purpose of this study was to evaluate the effectiveness of breaks on low back pain, discomfort, and work productivity in office workers. Publications were systematically searched in several databases from 1980 to December 2016. Relevant randomized and non-randomized controlled trials were retrieved and assessed for methodological quality by two independent reviewers. Quality of evidence was assessed and rated according to GRADE guidelines. Eight randomized controlled trials and three non-randomized controlled trials were included in this review, of which 10 were rated as high-quality studies. The break programs were highly heterogeneous with work duration ranging from 5 min to 2 h and break duration ranging from 20 s to 30 min. The results showed low-quality evidence for the conflicting effect of breaks on pain and low-quality evidence for the positive effect of breaks on discomfort. When stratified by type of breaks, moderate-quality evidence was found for the positive effect of active breaks with postural change for pain and discomfort. Moderate-quality evidence indicated that the use of breaks had no detrimental effect on work productivity. More high-quality studies are needed before recommendations can be given. Within a number of methodological limitations that are present in the published studies, active breaks with postural change may be effective in reducing pain in workers with acute low back pain and to prevent discomfort in healthy subjects.

Mindsets Matter: A New Framework for Harnessing the Placebo Effect in Modern Medicine

The clinical utility of the placebo effect has long hinged on physicians deceptively administering an objective placebo treatment to their patients. However, the power of the placebo does not reside in the sham treatment itself; rather, it comes from the psychosocial forces that surround the patient and the treatment. To this end, we propose a new framework for understanding and leveraging the placebo effect in clinical care. In outlining this framework, we first present the placebo effect as a neurobiological effect that is evoked by psychological processes. Next, we argue that along with implicit learning and expectation formation, mindsets are a key psychological process involved in the placebo effect. Finally, we illustrate the critical role of the social environment and treatment context in shaping these psychological processes. In doing so, we offer a guide for how the placebo effect can be understood, harnessed, and leveraged in the practice of modern medicine.

The periaqueductal gray and Bayesian integration in placebo analgesia

In placebo hypoalgesia research, the strength of treatment expectations and experiences are key components. However, the reliability or precision of expectations had been mostly ignored although being a likely source for interindividual differences. In the present study, we adopted a Bayesian framework, naturally combining expectation magnitudes and precisions. This postulates that expectations (prior) are integrated with incoming nociceptive information (likelihood) and both are weighted by their relative precision to form the pain percept and placebo effect. Sixty-two healthy subjects received heat pain during fMRI. Placebo effects were more pronounced in subjects with more precise treatment expectations and correlated positively with the relative precision of the prior expectation. Neural correlates of this precision were observed in the periaqueductal gray and the rostral ventromedial medulla, indicating that already at the level of the brainstem the precision of an expectation can influence pain perception presenting strong evidence for Bayesian integration in placebo hypoalgesia.

On a battlefield in World War II, surgeon Henry Beecher ran out of morphine. To his surprise, he found that replacing the missing morphine with saltwater allowed him to continue operating on wounded soldiers. Although saltwater contains no active pain-relieving ingredients, it reduced the soldiers’ pain. This is an example of the placebo effect. Placebos have been shown to reduce autonomic responses to pain, such as sweating. They also modulate activity in brain regions that process pain. But why do some of us experience larger placebo effects than others?

Grahl et al. propose that the size of the placebo effect depends on our expectations about a treatment. More specifically, it depends on how precise those expectations are. Imagine two people who have taken the same treatment many times, and who have experienced the same average reduction in pain. But for one person, the treatment reduced their pain by roughly the same amount each time. For the other, the treatment sometimes reduced their pain by a large amount and other times hardly at all. The first person will have more precise expectations than the second about how effective the treatment will be in future. Grahl et al. propose that the first person will thus experience a greater placebo effect in response to a ‘fake’ version of the treatment.

To test this idea, Grahl et al. applied painful heat to the forearms of healthy volunteers lying inside a brain scanner. On half the trials, the volunteers were told that they would also receive an electrical pain-relieving therapy. In reality, this treatment was never applied. After each trial, the volunteers rated the intensity of the pain they had experienced. As expected, the volunteers reported less pain when they thought they were receiving a pain-relieving treatment. Moreover, those volunteers with more precise expectations about the treatment reported greater pain relief than volunteers with less precise expectations. The former group also showed less activity in one of the brain’s major pain-processing centers, the periaqueductal gray.

These findings help shed light on why some people experience larger placebo effects than others. They suggest that helping patients form precise expectations about their treatment, by giving them precise information about its likely effectiveness, may boost the placebo effect. Further studies are needed to determine whether this phenomenon also occurs in patients with pain disorders. If it does, it could help such patients manage their pain using fewer active painkillers.

The Underestimated Significance of Conditioning in Placebo Hypoalgesia and Nocebo Hyperalgesia

Placebo and nocebo effects are intriguing phenomena in pain perception with important implications for clinical research and practice because they can alleviate or increase pain. According to current theoretical accounts, these effects can be shaped by verbal suggestions, social observational learning, and classical conditioning and are necessarily mediated by explicit expectation. In this review, we focus on the contribution of conditioning in the induction of placebo hypoalgesia and nocebo hyperalgesia and present accumulating evidence that conditioning independent from explicit expectation can cause these effects. Especially studies using subliminal stimulus presentation and implicit conditioning (i.e., without contingency awareness) that bypass the development of explicit expectation suggest that conditioning without explicit expectation can lead to placebo and nocebo effects in pain perception. Because only few studies have investigated clinical samples, the picture seems less clear when it comes to patient populations with chronic pain. However, conditioning appears to be a promising means to optimize treatment. In order to get a better insight into the mechanisms of placebo and nocebo effects in pain and the possible benefits of conditioning compared to explicit expectation, future studies should carefully distinguish both methods of induction.

Mechanisms of placebo analgesia: A dual-process model informed by insights from cross-species comparisons

Placebo treatments are pharmacologically inert, but are known to alleviate symptoms across a variety of clinical conditions. Associative learning and cognitive expectations both play important roles in placebo responses, however we are just beginning to understand how interactions between these processes lead to powerful effects. Here, we review the psychological principles underlying placebo effects and our current understanding of their brain bases, focusing on studies demonstrating both the importance of cognitive expectations and those that demonstrate expectancy-independent associative learning. To account for both forms of placebo analgesia, we propose a dual-process model in which flexible, contextually driven cognitive schemas and attributions guide associative learning processes that produce stable, long-term placebo effects. According to this model, the placebo-induction paradigms with the most powerful effects are those that combine reinforcement (e.g., the experience of reduced pain after placebo treatment) with suggestions and context cues that disambiguate learning by attributing perceived benefit to the placebo. Using this model as a conceptual scaffold, we review and compare neurobiological systems identified in both human studies of placebo analgesia and behavioral pain modulation in rodents. We identify substantial overlap between the circuits involved in human placebo analgesia and those that mediate multiple forms of context-based modulation of pain behavior in rodents, including forebrain-brainstem pathways and opioid and cannabinoid systems in particular. This overlap suggests that placebo effects are part of a set of adaptive mechanisms for shaping nociceptive signaling based on its information value and anticipated optimal response in a given behavioral context.

Effects of a stretching protocol for the pectoralis minor on muscle length, function, and scapular kinematics in individuals with and without shoulder pain

STUDY DESIGN

Parallel-group intervention with repeated measures.

INTRODUCTION

Shortening of the pectoralis minor (PM) may contribute to alterations in scapular kinematics.

PURPOSE OF THE STUDY

To evaluate the effects of a stretching protocol on function, muscle length, and scapular kinematics in subjects with and without shoulder pain.

METHODS

A sample of 25 patients with shoulder pain and 25 healthy subjects with PM tightness performed a daily stretching protocol for 6 weeks. Outcome measures included Disabilities of the Arm, Shoulder, and Hand questionnaire, PM length, and scapular kinematics.

RESULTS

Disabilities of the Arm, Shoulder, and Hand scores decreased (P < .05) in the patient group at post-intervention. No differences (P > .05) were found for PM length in both groups. Scapular anterior tilt increased (P < .05) at 90° of flexion in the healthy group.

DISCUSSION

This study demonstrated that a daily home stretching protocol significantly decreases pain and improves function in subjects with shoulder pain. The mechanism responsible for these improvements does not appear directly related to PM muscle length or scapula kinematics, suggesting that other neuromuscular mechanisms are involved.

CONCLUSION

The PM stretching protocol did not change the PM length or scapular kinematics in subjects with or without shoulder pain. However, pain and function of the upper limbs improved in patients with shoulder pain.

LEVEL OF EVIDENCE

2b.

Pain begets pain. When marathon runners are not in pain anymore, they underestimate their memory of marathon pain--A mediation analysis

BACKGROUND

A previous study has shown that memory of pain induced by running a marathon might be underestimated. However, little is known about the factors that might influence such a memory distortion during pain recall. The aim of the study was to investigate the memory of pain induced by running a marathon and the factors that might influence it: (1) present pain during recall and (2) recall delay.

METHODS

A total of 127 marathon runners participated in the study, which comprised of two phases. After completion of the marathon, participants were asked to rate the intensity and the unpleasantness of their pain. Either a week or a month later, they were asked again to rate the intensity and the unpleasantness of the remembered and present pain experience.

RESULTS

Participants underestimated remembered pain intensity and pain unpleasantness only if they did not experience pain during recall (p < 0.05). We observed a trend for underestimation after a week (p = 0.09) and significant effect after a month (p < 0.05) of recall delay. Furthermore, present pain intensity during recall significantly mediated the memory of pain intensity induced by running the marathon, but only after a month. Similarly, present pain unpleasantness during recall significantly mediated the memory of pain unpleasantness, but only after a month.

CONCLUSIONS

It is concluded that memory of pain induced by running the marathon is underestimated after a month of recall delay and mediated by present pain during recall.

SIGNIFICANCE

This study explores factors acting during recall, influencing memory of naturally occurring pain induced by physical effort. The empirical findings provide the first robust evidence for a causal relationship between memory of pain and present pain during recall.

Does conditioned pain modulation predict the magnitude of placebo effects in patients with neuropathic pain?

BACKGROUND

Conditioned pain modulation (CPM) is a validated measure of the function of endogenous pain inhibitory pathways. Placebo effects reflect top-down inhibitory modulation of pain. CPM and placebo effects are both influenced by expectations, albeit to varying degrees, and are related to neurotransmitter systems such as the endogenous opioid system, and it can be speculated that CPM responses are positively associated with the magnitude of placebo effects. Yet, no studies have tested this.

METHODS

The study included 19 patients with neuropathic pain. CPM was quantified as the difference in pressure pain threshold (PPT) as measured at the middle deltoid muscle before and after 5-min exposure to the cold pressor test (CPT) (conditioning pain stimulus). Placebo effects were tested via open and hidden applications of the pain-relieving agent lidocaine (2 mL) using a disinfection napkin controlled for no treatment.

RESULTS

The mean (SD) PPT was 668.7 (295.7) kPa before and 742.3 (370.8) kPa after the CPT. The mean (SD) CPM response was -73.6 (214.0) kPa corresponding to an 11% increase in PPT, reflecting a normally functioning endogenous pain modulatory system. Large and significant placebo effects were observed in ongoing neuropathic pain intensity (p = 0.002). The CPM response did not predict the magnitude of the placebo effect (p = 0.765). Moreover, there were no interaction effects for the moderator variables: clinical pain level (p = 0.136), age (p = 0.347) and gender (p = 0.691).

CONCLUSIONS

Conditioned pain modulation and placebo effects do not seem to be associated in patients with neuropathic pain.

SIGNIFICANCE

Conditioned pain modulation and placebo effects are endogenous pain-modulating phenomena that are influenced by some of the same mechanisms. This study suggests that CPM and placebo effects in neuropathic pain are independent phenomena that may be mediated by different mechanisms.

Molecular and functional PET-fMRI measures of placebo analgesia in episodic migraine: Preliminary findings

Pain interventions with no active ingredient, placebo, are sometimes effective in treating chronic pain conditions. Prior studies on the neurobiological underpinnings of placebo analgesia indicate endogenous opioid release and changes in brain responses and functional connectivity during pain anticipation and pain experience in healthy subjects. Here, we investigated placebo analgesia in healthy subjects and in interictal migraine patients (n = 9) and matched healthy controls (n = 9) using ¹¹C-diprenoprhine Positron Emission Tomography (PET) and simultaneous functional Magnetic Resonance Imaging (fMRI). Intravenous saline injections (the placebo) led to lower pain ratings, but we did not find evidence for an altered placebo response in interictal migraine subjects as compared to healthy subjects.

Route of placebo administration: Robust placebo effects in laboratory and clinical settings

Recent advances in laboratory and clinical research have greatly enhanced our understanding of placebo effects. However, little progress has been made in translational research that can well integrate these findings. This article examines pivotal role of placebo administration in subsequent placebo responses, providing a unified framework that accounts for robust placebo effects in both laboratory and clinical settings.

Effects of explicit cueing and ambiguity on the anticipation and experience of a painful thermal stimulus

Many factors can influence the way in which we perceive painful events and noxious stimuli, but less is known about how pain perception is altered by explicit knowledge about the impending sensation. This study aimed to investigate the impact of explicit cueing on anxiety, arousal, and pain experience during the anticipation and delivery of noxious thermal heat stimulations. Fifty-two healthy volunteers were randomised to receive explicit instructions about visual cue-stimulus temperature pairings, or no explicit instructions about the cue-stimulus pairs. A pain anxiety task was used to investigate the effects of explicit cueing on anticipatory anxiety, pain experience and electrophysiological responses. Participants who received explicit instructions about the cue-stimulus pairs (i.e., the relationship between the colour of the cue and the temperature of the associated stimuli) reported significantly higher subjective anxiety prior to the delivery of the thermal heat stimuli (p = .025, partial eta squared = .10). There were no effects of explicit cueing on subsequent pain intensity, unpleasantness, or the electrophysiological response to stimulus delivery. The perceived intensity and unpleasantness of the stimuli decreased across the blocks of the paradigm. In both groups anticipating the ambiguous cue elicited the largest change in electrophysiological arousal, indicating that not knowing the impending stimulus temperature led to increased arousal, compared to being certain of receiving a high temperature thermal stimulus (both p < .001). Perceived stimulus intensity varied between ambiguous and non-ambiguous cues, depending on the temperature of the stimulus. Together these findings highlight the impact and importance of explicit cueing and uncertainty in experimental pain studies, and how these factors influence the way healthy individuals perceive and react to noxious and innocuous thermal stimuli.

Classical conditioning without verbal suggestions elicits placebo analgesia and nocebo hyperalgesia

The aim of this study was to examine the relationships among classical conditioning, expectancy, and fear in placebo analgesia and nocebo hyperalgesia. A total of 42 healthy volunteers were randomly assigned to three groups: placebo, nocebo, and control. They received 96 electrical stimuli, preceded by either orange or blue lights. A hidden conditioning procedure, in which participants were not informed about the meaning of coloured lights, was performed in the placebo and nocebo groups. Light of one colour was paired with pain stimuli of moderate intensity (control stimuli), and light of the other colour was paired with either nonpainful stimuli (in the placebo group) or painful stimuli of high intensity (in the nocebo group). In the control group, both colour lights were followed by control stimuli of moderate intensity without any conditioning procedure. Participants rated pain intensity, expectancy of pain intensity, and fear. In the testing phase, when both of the coloured lights were followed by identical moderate pain stimuli, we found a significant analgesic effect in the placebo group, and a significant hyperalgesic effect in the nocebo group. Neither expectancy nor fear ratings predicted placebo analgesia or nocebo hyperalgesia. It appears that a hidden conditioning procedure, without any explicit verbal suggestions, elicits placebo and nocebo effects, however we found no evidence that these effects are predicted by either expectancy or fear. These results suggest that classical conditioning may be a distinct mechanism for placebo and nocebo effects.

The Cognitive Neuroscience of Placebo Effects: Concepts, Predictions, and Physiology

Placebos have been used ubiquitously throughout the history of medicine. Expectations and associative learning processes are important psychological determinants of placebo effects, but their underlying brain mechanisms are only beginning to be understood. We examine the brain systems underlying placebo effects on pain, autonomic, and immune responses. The ventromedial prefrontal cortex (vmPFC), insula, amygdala, hypothalamus, and periaqueductal gray emerge as central brain structures underlying placebo effects. We argue that the vmPFC is a core element of a network that represents structured relationships among concepts, providing a substrate for expectations and a conception of the situation-the self in context-that is crucial for placebo effects. Such situational representations enable multidimensional predictions, or priors, that are combined with incoming sensory information to construct percepts and shape motivated behavior. They influence experience and physiology via descending pathways to physiological effector systems, including the spinal cord and other peripheral organs.

Placebo-related effects: a meta-narrative review of conceptualization, mechanisms and their relevance in rheumatology

For decades in medicine, the placebo effect has been conceptualized as a subjective psychological effect associated with an inert substance and considered to be a nuisance noise in the assessment of therapeutic effects in clinical trials. However, research on placebo has undergone substantial developments since the mid-1980s in several fields of knowledge (including methodology, psychology and neurosciences) that challenge this traditional view. Using a meta-narrative approach, this review of conceptualizations, determinants, mechanisms and models of placebo effects shows that placebo effects are genuine biopsychosocial phenomena strongly affected by context and factors surrounding the patient and treatments. Psychological experiments and neurobiological and neuroimaging studies have identified various types of placebo responses, driven by different mechanisms (especially but not only expectation and conditioning) and associated with different chemical, structural and functional features. Insights into the mechanisms involved in placebo responses have led to opportunities for ethical enhancements of these mechanisms in clinical practice, notably by improving the patient-doctor interaction and refining the therapeutic ritual. These developments should be carefully considered in rheumatology settings, in which placebo effects are both prevalent and significant, with the potential to improve patient care.