The Placebo Effect in Pain Therapies

What is the nocebo effect and does it apply to dentistry? A narrative review

Background

Evidence for the nocebo effect, a phenomenon characterised by suboptimal treatment efficacy, worsening of symptoms, or the occurrence of adverse events caused by an individual’s negative treatment expectations, is growing across a multitude of medical fields. However, little attention has been paid to patients’ negative expectations and the nocebo effect within dentistry.

Aim

This review summarises essential evidence of the nocebo phenomenon especially in relation to pain and drug administration. Subsequently, an overview of the current evidence of the nocebo phenomenon in the dental field is presented.

Methods

A PubMed search was performed using keywords related to “nocebo,” “placebo,” “expectations,” and “dentistry.” In addition to the articles selected from the search, placebo/nocebo researchers and dental researchers added important references from their respective fields.

Results

Although research on the nocebo effect in dentistry is limited, available current evidence suggests that the factors, which is related to the nocebo effect are likely to play a role in dental practice.

Conclusion

Preliminary evidence from the review warrants further investigation into the nocebo effect in dentistry. Finally, based on the general knowledge of the nocebo effect, the review indicates fruitful arrays of research into the nocebo effect in dentistry.

Optimising treatment expectations in chronic lower back pain through observing others: a study protocol for a randomised clinical trial

INTRODUCTION

Chronic lower back pain (CLBP) is a frequent cause of medical consultations worldwide, and it results in decreased quality of life and disability. Current treatments for CLBP are often not effective, and alternatives are urgently needed. Three promising possibilities have emerged: (1) open-label placebo treatment reduces chronic pain, (2) placebo treatment is as efficacious as opioid treatment with a high correlation between patient expectation and treatment outcome, and (3) observing positive effects in another patient can improve functional capacity. We hypothesise that treatment expectations can be positively influenced through social observation and improve treatment outcome.

METHODS AND ANALYSIS

In our clinical trial, we will randomise patients with CLBP into five groups. Two groups receive either a 3 week course of treatment with an analgesic (ANA) (metamizole/dipyrone) or with open-label placebos (OLP). For one of each group, we will build treatment expectations through observational learning and assess its impact on the treatment. For this purpose, one group each will watch either a positive or a neutral video. The intervention groups will be compared with a control group that will not be given any medication or observational learning. Participants will be recruited via all institutions in the Hamburg metropolitan area that treat patients with CLBP. Patients are eligible for inclusion if they are at least 18 years or older, have CLBP (of at least 3 months duration), and agree to potentially receive an active ANA or an OLP. Patients with pain-related "red flags" will be excluded. The study requires 150 participants (30 participants per group) to assess the differences in the primary outcome, pain intensity. Secondary outcomes include changes in treatment expectations, anxiety, comorbid depression, stress-related neuroendocrine measures, functional and structural connectivity, functional capacity, and ANA consumption. All outcomes and treatment expectations will be measured before and after the intervention and 3 months post-intervention.

ETHICS AND DISSEMINATION

Ethical approval was obtained in January 2020 from the Hamburg Medical Ethics Council (ref number PV7067). Outcomes will be disseminated through publications in peer-reviewed journals and presentations at national and international conference meetings.

TRIAL REGISTRATION NUMBER

The approved trial protocol was registered at the German Clinical Trials Register (DRKS) and can be found at drks.de (Identifier: DRKS00024418).

Educational Intervention for Management of Acute Trauma Pain: A Proof-of-Concept Study in Post-surgical Trauma Patients

OBJECTIVE

Despite years of research and the development of countless awareness campaigns, the number of deaths related to prescription opioid overdose is steadily rising. Often, naive patients undergoing trauma-related surgery are dispensed opioids while in the hospital, resulting in an escalation to long-term opioid misuses. We explored the impact of an educational intervention to modify perceptions of opioid needs at the bedside of trauma inpatients in post-surgery pain management.

MATERIALS AND METHODS

Twenty-eight inpatients with acute post-surgical pain completed this proof-of-concept study adopting an educational intervention related to opioids and non-pharmacological strategies in the context of acute post-surgical pain. An education assessment survey was developed to measure pre- and post-education perceptions of opioid needs to manage pain. The survey statements encompassed the patient's perceived needs for opioids and other pharmacological and non-pharmacological therapeutics to manage acute pain. The primary outcome was the change in the patient's perceived need for opioids. The secondary (explorative) outcome was the change in Morphine Milligram Equivalents (MME) used on the day of the educational intervention while inpatients and prescribed at the time of the hospital discharge.

RESULTS

After the educational intervention, patients reported less agreement with the statement, "I think a short course of opioids (less than 5 days) is safe." Moreover, less agreement on using opioids to manage trauma-related pain was positively associated with a significant reduction in opioids prescribed at discharge after the educational intervention. The educational intervention might have effectively helped to cope with acute trauma-related pain while adjusting potential unrealistic expectancies about pain management and, more in general, opioid-related needs.

CONCLUSION

These findings suggest that trauma patients' expectations and understanding of the risks associated with the long-term use of opioids can be modified by a short educational intervention delivered by health providers during the hospitalization. Establishing realistic expectations in managing acute traumatic pain may empower patients with the necessary knowledge to minimize the potential of continuous long-term opioid use, opioid misuse, and the development of post-trauma opioid abuse and/or addiction.

Placebo and hypnosis in the clinical setting: Contextual factors in hypnotic analgesia

The assumption that hypnotic analgesia produces placebo effects is controversial. The cognitive dimension that can distinguish hypnosis from placebo analgesia has been suggested as hypnotic susceptibility. The aim of this study is to investigate the role of the relationship between patient and therapist, assumed to produce the placebo effect, in the clinical context of hypnotic treatment for pain. Seventy subjects were given hypnosis administered by the therapist in person (Group A) and 37 practiced self-hypnosis (Group B) for 8 weeks. The Somatosensory Amplification Scale (SSAS), Stanford hypnotic susceptibility scale type A, Cold pressor test (CPT) and SCL-90 were administered at baseline, and Italian Pain Questionnaire (IPQ) dimensions were used as outcome measures. The SSAS did appear to reflect the efficacy of hypnotic analgesia in all pain variables explored, but only in Group B. An improvement in pain intensity and all IPQ dimensions were found at 8 weeks. In particular, an improvement in the affective dimension of pain, with a medium-high effect size (η2 = .774), was recorded after hypnotic analgesia, with the outcome being better in Group A than in Group B (p = .001). This outcome was independent of hypnotic susceptibility in both groups. Considering our hypothesis that, given the administration of the same suggestions, the therapist could promote the placebo response, contributing to the improvement in the affective dimension of pain outcome, which exhibited a response to the hypnotic treatment independently of hypnotic susceptibility.

The threshold tracking nerve conduction study technique: Experience of clinical users unfamiliar with a research-grade neuronal excitability system

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Threshold tracking nerve conduction studies (TTNCSs) measure axon excitability.

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TTNCSs can objectively characterize neuronal dysfunction and treatment response.

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An available research-grade TTNCS system has not been widely implemented .

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Clinical electrophysiologists with varying levels of experience can perform TTNCSs.

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A user-friendly system and education about TTNCSs could broaden use of the technique.

Objective

To 1) explore if clinical electrophysiologists with different degrees of experience performing standard nerve conduction studies could run a threshold tracking nerve conduction study (TTNCS) protocol and 2) learn how clinical users view a research-grade TTNCSs neuronal excitability system.

Methods

Five clinical electrophysiologists conducted a TTNCS session using QTracS and then completed a questionnaire describing their impressions.

Results

All of the electrophysiologists completed the QTracS protocol on an initial attempt. Perceived strengths comprised the ease of preparatory steps and quick protocol speed. Identified drawbacks included an unwieldly user-interface. The electrophysiologists indicated that knowledge of TTNCS principles and applications would be critical for incorporation of the method into clinical use.

Conclusions

This pilot study suggests that clinical electrophysiologists can carry out TTNCSs with a research-grade system. The development of a more user-friendly program, along with dedicated education and training, could lead to wider application of the TTNCS technique.

Significance

Considered together with clinical presentation and other biomarkers, increased use of TTNCSs could provide improved assessment of neuromuscular disease and treatment response.

Conditioning to Enhance the Effects of Repetitive Transcranial Magnetic Stimulation on Experimental Pain in Healthy Volunteers

OBJECTIVE

In this proof-of-concept study we sought to explore whether the combination of conditioning procedure based on a surreptitious reduction of a noxious stimulus (SRPS) could enhance rTMS hypoalgesic effects [i.e., increase heat pain threshold (HPT)] and augment intervention expectations in a healthy population.

METHODS

Forty-two healthy volunteers (19-35 years old) were enrolled in a randomized crossover-controlled study and were assigned to one of two groups: (1) SRPS and (2) No SRPS. Each participant received two consecutive sessions of active or sham rTMS over the M1 area of the right hand on two visits (1) active, (2) sham rTMS separated by at least one-week interval. HPT and the temperature needed to elicit moderate heat pain were measured before and after each rTMS intervention on the right forearm. In the SRPS group, conditioning consisted of deliberately decreasing thermode temperature by 3°C following intervention before reassessing HPT, while thermode temperature was held constant in the No SRPS group. Intervention expectations were measured before each rTMS session.

RESULTS

SRPS conditioning procedure did not enhance hypoalgesic effects of rTMS intervention, neither did it modify intervention expectations. Baseline increases in HPT were found on the subsequent intervention session, suggesting variability of this measure over time, habituation or a possible "novelty effect."

CONCLUSION

Using a SRPS procedure in healthy volunteers did not enhance rTMS modulating effects on experimental pain sensation (i.e., HPT). Future studies are therefore needed to come up with a conditioning procedure which allows significant enhancement of rTMS pain modulating effects in healthy volunteers.

Consensus practice guidelines on interventions for cervical spine (facet) joint pain from a multispecialty international working group

BACKGROUND

The past two decades have witnessed a surge in the use of cervical spine joint procedures including joint injections, nerve blocks and radiofrequency ablation to treat chronic neck pain, yet many aspects of the procedures remain controversial.

METHODS

In August 2020, the American Society of Regional Anesthesia and Pain Medicine and the American Academy of Pain Medicine approved and charged the Cervical Joint Working Group to develop neck pain guidelines. Eighteen stakeholder societies were identified, and formal request-for-participation and member nomination letters were sent to those organizations. Participating entities selected panel members and an ad hoc steering committee selected preliminary questions, which were then revised by the full committee. Each question was assigned to a module composed of 4-5 members, who worked with the Subcommittee Lead and the Committee Chairs on preliminary versions, which were sent to the full committee after revisions. We used a modified Delphi method whereby the questions were sent to the committee en bloc and comments were returned in a non-blinded fashion to the Chairs, who incorporated the comments and sent out revised versions until consensus was reached. Before commencing, it was agreed that a recommendation would be noted with >50% agreement among committee members, but a consensus recommendation would require ≥75% agreement.

RESULTS

Twenty questions were selected, with 100% consensus achieved in committee on 17 topics. Among participating organizations, 14 of 15 that voted approved or supported the guidelines en bloc, with 14 questions being approved with no dissensions or abstentions. Specific questions addressed included the value of clinical presentation and imaging in selecting patients for procedures, whether conservative treatment should be used before injections, whether imaging is necessary for blocks, diagnostic and prognostic value of medial branch blocks and intra-articular joint injections, the effects of sedation and injectate volume on validity, whether facet blocks have therapeutic value, what the ideal cut-off value is for designating a block as positive, how many blocks should be performed before radiofrequency ablation, the orientation of electrodes, whether larger lesions translate into higher success rates, whether stimulation should be used before radiofrequency ablation, how best to mitigate complication risks, if different standards should be applied to clinical practice and trials, and the indications for repeating radiofrequency ablation.

CONCLUSIONS

Cervical medial branch radiofrequency ablation may provide benefit to well-selected individuals, with medial branch blocks being more predictive than intra-articular injections. More stringent selection criteria are likely to improve denervation outcomes, but at the expense of false-negatives (ie, lower overall success rate). Clinical trials should be tailored based on objectives, and selection criteria for some may be more stringent than what is ideal in clinical practice.

Positive Treatment Expectations Shape Perceived Medication Efficacy in a Translational Placebo Paradigm for the Gut-Brain Axis

Placebo research has established the pivotal role of treatment expectations in shaping symptom experience and patient-reported treatment outcomes. Perceived treatment efficacy constitutes a relevant yet understudied aspect, especially in the context of the gut-brain axis with visceral pain as key symptom. Using a clinically relevant experimental model of visceral pain, we elucidated effects of pre-treatment expectations on post-treatment perceived treatment efficacy as an indicator of treatment satisfaction in a translational placebo intervention. We implemented positive suggestions regarding intravenous treatment with a spasmolytic drug (in reality saline), herein applied in combination with two series of individually calibrated rectal distensions in healthy volunteers. The first series used distension pressures inducing pain (pain phase). In the second series, pressures were surreptitiously reduced, modeling pain relief (pain relief phase). Using visual analog scales (VAS), expected and perceived treatment efficacy were assessed, along with perceived pain intensity. Manipulation checks supported that the induction of positive pre-treatment expectations and the modeling of pain relief were successful. Generalized Linear Models (GLM) were implemented to assess the role of inter-individual variability in positive pre-treatment expectations in perceived treatment efficacy and pain perception. GLM indicated no association between pre-treatment expectations and perceived treatment efficacy or perceived pain for the pain phase. For the relief phase, pre-treatment expectations (p = 0.024) as well as efficacy ratings assessed after the preceding pain phase (p < 0.001) were significantly associated with treatment efficacy assessed after the relief phase, together explaining 54% of the variance in perceived treatment efficacy. The association between pre-treatment expectations and perceived pain approached significance (p = 0.057) in the relief phase. Our data from an experimental translational placebo intervention in visceral pain support that reported post-treatment medication efficacy is shaped by pre-treatment expectations. The observation that individuals with higher positive expectations reported less pain and higher treatment satisfaction after pain relief may provide first evidence that perceived symptom improvement may facilitate treatment satisfaction. The immediate experience of symptoms within a given psychosocial treatment context may dynamically change perceptions about treatment, with implications for treatment satisfaction, compliance and adherence of patients with conditions of the gut-brain axis.

Psychedelics in the Treatment of Headache and Chronic Pain Disorders

The therapeutic potential of psychedelics in headache and chronic pain disorders is documented over decades of anecdotal and early investigational reports, which have paved the way for the first controlled studies of psilocybin and lysergic acid diethylamide (LSD) in these disorders. The reported lasting clinical effects after limited dosing with psychedelics present a novel means for disease management, but considerable further study will be required to address disease-specific treatments, uncover mechanism(s) of action, and verify safety. In this chapter, these topics are reviewed with particular attention to the neurobiological systems that offer potential sources of psychedelics' unique clinical effects in headache and pain.

The placebo and nocebo effects in functional urology

A placebo is an inert substance normally used in clinical trials for comparison with an active substance. However, a placebo has been shown to have an effect on its own; commonly known as the placebo effect. A placebo is an essential component in the design of conclusive clinical trials but has itself become the focus of intense research. The placebo effect is partly the result of positive expectations of the recipient on the state of health. Conversely, a nocebo effect is when negative expectations from a substance lead to poor treatment outcomes and/or adverse events. Randomized controlled trials in functional urology have demonstrated the importance of the placebo and nocebo effects across different diseases such as overactive bladder, urinary incontinence, lower urinary tract symptoms and interstitial cystitis/painful bladder syndrome, as well as male and female sexual dysfunction. Understanding the true nature of the placebo-nocebo complex and the scope of its effect in functional urology could help urologists to maximize the positive effects of this phenomenon while minimizing its potentially negative effects.

Consensus practice guidelines on interventions for cervical spine (facet) joint pain from a multispecialty international working group

BACKGROUND

The past two decades have witnessed a surge in the use of cervical spine joint procedures including joint injections, nerve blocks and radiofrequency ablation to treat chronic neck pain, yet many aspects of the procedures remain controversial.

METHODS

In August 2020, the American Society of Regional Anesthesia and Pain Medicine and the American Academy of Pain Medicine approved and charged the Cervical Joint Working Group to develop neck pain guidelines. Eighteen stakeholder societies were identified, and formal request-for-participation and member nomination letters were sent to those organizations. Participating entities selected panel members and an ad hoc steering committee selected preliminary questions, which were then revised by the full committee. Each question was assigned to a module composed of 4-5 members, who worked with the Subcommittee Lead and the Committee Chairs on preliminary versions, which were sent to the full committee after revisions. We used a modified Delphi method whereby the questions were sent to the committee en bloc and comments were returned in a non-blinded fashion to the Chairs, who incorporated the comments and sent out revised versions until consensus was reached. Before commencing, it was agreed that a recommendation would be noted with >50% agreement among committee members, but a consensus recommendation would require ≥75% agreement.

RESULTS

Twenty questions were selected, with 100% consensus achieved in committee on 17 topics. Among participating organizations, 14 of 15 that voted approved or supported the guidelines en bloc, with 14 questions being approved with no dissensions or abstentions. Specific questions addressed included the value of clinical presentation and imaging in selecting patients for procedures, whether conservative treatment should be used before injections, whether imaging is necessary for blocks, diagnostic and prognostic value of medial branch blocks and intra-articular joint injections, the effects of sedation and injectate volume on validity, whether facet blocks have therapeutic value, what the ideal cut-off value is for designating a block as positive, how many blocks should be performed before radiofrequency ablation, the orientation of electrodes, whether larger lesions translate into higher success rates, whether stimulation should be used before radiofrequency ablation, how best to mitigate complication risks, if different standards should be applied to clinical practice and trials, and the indications for repeating radiofrequency ablation.

CONCLUSIONS

Cervical medial branch radiofrequency ablation may provide benefit to well-selected individuals, with medial branch blocks being more predictive than intra-articular injections. More stringent selection criteria are likely to improve denervation outcomes, but at the expense of false-negatives (ie, lower overall success rate). Clinical trials should be tailored based on objectives, and selection criteria for some may be more stringent than what is ideal in clinical practice.

Effect of White Willow Bark on Delayed Onset Muscle Soreness Following Resistance Training: A Pilot Study

OBJECTIVES Delayed onset muscle soreness (DOMS) is discomfort that occurs within 8-24hrs following an unaccustomed bout of physical activity that peaks within 24-27hrs and slowly resolves on its own. White willow bark (WWB) is a nutritional supplement that is believed to have anti-inflammatory and analgesic properties like aspirin but without the risk of GI adverse effects. The purpose of this investigation is to determine the effectiveness of WWB on alleviating the symptoms of DOMS following exercise.METHODS Twenty-five individuals volunteered to participate and were randomly assigned to take WWB (798mg salicin) or placebo for 5 days following a lower body resistance training session which consisted of 5X10 lunges at 40% body weight (BW) and 3X fatigue leg press at 75%BW. Test procedures included visual analog scale (VAS), mid-thigh circumference and pressure pain threshold. VAS was measured pre, all five days of the supplementation period and day 6 (post-supplementation). All other variables were measured at pre, immediate, day 3(72hrs), and day 6 (post-supplementation).RESULTS No condition X time interaction was observed (p > 0.05) for any variable. However, VAS scores were lower in the WWB compared to the placebo for all time frames. There was a significant main effect of time for VAS scores indicating muscle soreness for hamstrings (p < 0.001), gluteal (p < 0.001), gastrocnemius (p < 0.001) and quadriceps (p < 0.001). In addition, there was a significant main effect of time for right midthigh pressure pain threshold (p = 0.02), mid-right (p < 0.001) and mid-left (p < 0.001) thigh circumference.CONCLUSIONS WWB may reduce subjective feelings of muscle soreness and appears to have analgesic properties.

Placebo effect in pharmacological management of fibromyalgia: a meta-analysis

INTRODUCTION

The management of fibromyalgia involves a combination of pharmacological and non-pharmacological treatments.

SOURCE OF DATA

Recently published literature in PubMed, Google Scholar and Embase databases.

AREAS OF AGREEMENT

Several pharmacological and non-pharmacological strategies have been proposed for the management of fibromyalgia. However, the management of fibromyalgia remains controversial. The administration of placebo has proved to be more effective than no treatment in many clinical settings and evidence supports the 'therapeutic' effects of placebo on a wide range of symptoms.

AREAS OF CONTROVERSY

The placebo effect is believed to impact the clinical outcomes, but its actual magnitude is controversial.

GROWING POINTS

A meta-analysis comparing pharmacological management versus placebo administration for fibromyalgia was conducted.

AREAS TIMELY FOR DEVELOPING RESEARCH

Drug treatment resulted to be more effective than placebo administration for the management of fibromyalgia. Nevertheless, placebo showed a beneficial effect in patients with fibromyalgia. Treatment-related adverse events occurred more frequently in the drug treatment.

LEVEL OF EVIDENCE

I, Bayesian network meta-analysis of double-blind randomized clinical trials.

Placebo comparator group selection and use in surgical trials: the ASPIRE project including expert workshop

BACKGROUND

The use of placebo comparisons for randomised trials assessing the efficacy of surgical interventions is increasingly being considered. However, a placebo control is a complex type of comparison group in the surgical setting and, although powerful, presents many challenges.

OBJECTIVES

To provide a summary of knowledge on placebo controls in surgical trials and to summarise any recommendations for designers, evaluators and funders of placebo-controlled surgical trials.

DESIGN

To carry out a state-of-the-art workshop and produce a corresponding report involving key stakeholders throughout.

SETTING

A workshop to discuss and summarise the existing knowledge and to develop the new guidelines.

RESULTS

To assess what a placebo control entails and to assess the understanding of this tool in the context of surgery is considered, along with when placebo controls in surgery are acceptable (and when they are desirable). We have considered ethics arguments and regulatory requirements, how a placebo control should be designed, how to identify and mitigate risk for participants in these trials, and how such trials should be carried out and interpreted. The use of placebo controls is justified in randomised controlled trials of surgical interventions provided that there is a strong scientific and ethics rationale. Surgical placebos might be most appropriate when there is poor evidence for the efficacy of the procedure and a justified concern that results of a trial would be associated with a high risk of bias, particularly because of the placebo effect.

CONCLUSIONS

The use of placebo controls is justified in randomised controlled trials of surgical interventions provided that there is a strong scientific and ethics rationale. Feasibility work is recommended to optimise the design and implementation of randomised controlled trials. An outline for best practice was produced in the form of the Applying Surgical Placebo in Randomised Evaluations (ASPIRE) guidelines for those considering the use of a placebo control in a surgical randomised controlled trial.

LIMITATIONS

Although the workshop participants involved international members, the majority of participants were from the UK. Therefore, although every attempt was made to make the recommendations applicable to all health systems, the guidelines may, unconsciously, be particularly applicable to clinical practice in the UK NHS.

FUTURE WORK

Future work should evaluate the use of the ASPIRE guidelines in making decisions about the use of a placebo-controlled surgical trial. In addition, further work is required on the appropriate nomenclature to adopt in this space.

FUNDING

Funded by the Medical Research Council UK and the National Institute for Health Research as part of the Medical Research Council-National Institute for Health Research Methodology Research programme.

Thirty Years of Neuroscientific Investigation of Placebo and Nocebo: The Interesting, the Good, and the Bad

Over the past 30 years there has been a surge of research on the placebo effect using a neuroscientific approach. The interesting aspects of this effort are related to the identification of several biological mechanisms of both the placebo and nocebo effects, the latter of which is defined as a negative placebo effect. Some important translational implications have emerged both in the setting of clinical trials and in routine medical practice. One of the principal contributions of neuroscience has been to draw the attention of the scientific and medical communities to the important role of psychobiological factors in therapeutic outcomes, be they drug related or not. Indeed, many biological mechanisms triggered by placebos and nocebos resemble those modulated by drugs, suggesting a possible interaction between psychological factors and drug action. Unfortunately, this new knowledge regarding placebos has the potential of being dangerously exploited by pseudoscience. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Pancreatic Pain-Knowledge Gaps and Research Opportunities in Children and Adults: Summary of a National Institute of Diabetes and Digestive and Kidney Diseases Workshop

ABSTRACT

A workshop was sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases to focus on research gaps and opportunities in pancreatic pain. The event was held on July 21, 2021, and structured into 4 sessions: (1) pathophysiology; (2) biomarkers, mediators, and pharmacology of pain; (3) pain assessment; and (4) pain treatment challenges and opportunities. The current state of knowledge was reviewed; many knowledge gaps and research needs were identified that require further investigation. Common themes included the need to better understand the underlying mechanisms of pain in pancreatic diseases, the relationship of visceral neural pathways and central pain centers, the role of behavioral factors and disorders on the perception of pain, and differences in pain perception and processes in children when compared with adults. In addition, the role of genetic risk factors for pain and the mechanisms and role of placebos in pain treatment were discussed. Methods of pain assessment including quantitative sensory testing were examined, as well as the process of central sensitization of pain. Finally, newer approaches to pain management including cognitive behavioral therapy, nerve stimulation, experimental (nonopioid) drugs, and cannabinoid compounds were covered.

Comparing the Impact of Multi-Session Left Dorsolateral Prefrontal and Primary Motor Cortex Neuronavigated Repetitive Transcranial Magnetic Stimulation (nrTMS) on Chronic Pain Patients

Repetitive transcranial stimulation (rTMS) has been shown to produce an analgesic effect and therefore has a potential for treating chronic refractory pain. However, previous studies used various stimulation parameters (including cortical targets), and the best stimulation protocol is not yet identified. The present study investigated the effects of multi-session 20 Hz (2000 pulses) and 5 Hz (1800 pulses) rTMS stimulation of left motor cortex (M1-group) and left dorsolateral prefrontal cortex (DLPFC-group), respectively. The M1-group (n = 9) and DLPFC-group (n = 7) completed 13 sessions of neuronavigated stimulation, while a Sham-group (n = 8) completed seven sessions of placebo stimulation. The outcome was measured using the German Pain Questionnaire (GPQ), Depression, Anxiety and Stress Scale (DASS), and SF-12 questionnaire. Pain perception significantly decreased in the DLPFC-group (38.17%) compared to the M1-group (56.11%) (p ≤ 0.001) on the later sessions. Health-related quality of life also improved in the DLPFC-group (40.47) compared to the Sham-group (35.06) (p = 0.016), and mental composite summary (p = 0.001) in the DLPFC-group (49.12) compared to M1-group (39.46). Stimulation of the left DLPFC resulted in pain relief, while M1 stimulation was not effective. Nonetheless, further studies are needed to identify optimal cortical target sites and stimulation parameters.

What can be done to control the placebo response in clinical trials? A narrative review

The desire to reduce high placebo response rates in clinical trials is a popular concept. However, few studies have rigorously examined the effectiveness of methods to control for placebo responses that are relevant to randomized controlled trials. The primary objective of this review was to evaluate the effect of experimental placebo manipulations in randomized controlled trials (RCTs). We critically reviewed studies designed to manipulate placebo responses including positive expectations regarding the effectiveness of the placebo treatment, manipulating the time spent with subjects, and training study staff and subjects to accurately report symptom severity. These efforts have generally resulted in reduced placebo response and improved discrimination between drug and placebo. Interventions that neutralize staff and subject expectations and improve the ability of subjects to accurately report symptom severity have shown the most promise. Reduction of the placebo response has the potential to accelerate the development of new therapeutics.

Quantitative language features identify placebo responders in chronic back pain

ABSTRACT

Although placebo effect sizes in clinical trials of chronic pain treatments have been increasing, it remains unknown if characteristics of individuals' thoughts or previous experiences can reliably infer placebo pill responses. Research using language to investigate emotional and cognitive processes has recently gained momentum. Here, we quantified placebo responses in chronic back pain using more than 300 semantic and psycholinguistic features derived from patients' language. This speech content was collected in an exit interview as part of a clinical trial investigating placebo analgesia (62 patients, 42 treated; 20 not treated). Using a nested leave-one-out cross-validated approach, we distinguished placebo responders from nonresponders with 79% accuracy using language features alone; a subset of these features-semantic distances to identity and stigma and the number of achievement-related words-also explained 46% of the variance in placebo analgesia. Importantly, these language features were not due to generic treatment effects and were associated with patients' specific baseline psychological traits previously shown to be predictive of placebo including awareness and personality characteristics, explaining an additional 31% of the variance in placebo analgesia beyond that of personality. Initial interpretation of the features suggests that placebo responders differed in how they talked about negative emotions and the extent that they expressed awareness to various aspects of their experiences; differences were also seen in time spent talking about leisure activities. These results indicate that patients' language is sufficient to identify a placebo response and implie that specific speech features may be predictive of responders' previous treatment.

Patient Expectancy Does Not Predict Success or Failure of Thermal Neurotomy for Persistent Zygapophysial and Sacroiliac Joint Pain

OBJECTIVE

The placebo effect is important in determining the outcome of the treatment of pain for which expectancy and context are the main contributors. The variable success of thermal neurotomy spinal pain procedures is often seen as evidence of the placebo effect. Conversely, proponents of pain procedures explain poorer outcomes by technical procedure deficiencies, including inadequate diagnosis. This cohort study set out to determine whether patient expectancy is a contributing factor in the outcome of thermal neurotomy to the cervical, thoracic, and lumbar zygapophysial and sacroiliac joints.

DESIGN

This single-practitioner, single-site retrospective analysis of prospectively gathered cohort data of 549 patients evaluated the impact of patient preprocedure expectancy (rated on a simple 0-10 or 0-4 numerical rating scale) on outcomes in a large consecutive series of patients who had undergone thermal neurotomy treatment between 2009 and 2019. In addition, a portion of patients were asked to what extent they hoped for or desired a good outcome.

RESULTS

Successful pain relief (≥75% reduction from baseline) was not associated with a higher preprocedure expectancy than were failed procedures. Hope and desire demonstrated no impact on the positive or negative impact of the procedure.

CONCLUSIONS

Altogether, patient expectation of outcome, hope, and desire are not associated with the outcome of effective pain relief by thermal neurotomy that has been performed to the appropriate and commonly available technical standards. Further work is needed to determine the influence of patient expectation across a range of pain intervention modalities.

Exploring patient views of empathic optimistic communication for osteoarthritis in primary care: a qualitative interview study using vignettes

Background

Osteoarthritis (OA) causes pain and disability. An empathic optimistic consultation approach can improve patient quality of life, satisfaction with care, and reduce pain. However, expressing empathic optimism may be overlooked in busy primary care consultations and there is limited understanding of patients’ views about this approach.

Aim

To explore patients’ perspectives on clinician communication of empathy and optimism in primary care OA consultations.

Design & setting

Vignette study with qualitative semi-structured interviews. Purposefully sampled patients (n = 33) aged >45 years with hip or knee OA from GP practices in Wessex (Hampshire, Dorest, Wiltshire, and Somerset).

Method

Fifteen participants watched two filmed OA consultations with a GP, and 18 participants read two case vignettes. In both formats, one GP depicted an empathic optimistic approach and one GP had a ‘neutral’ approach. Semi-structured interviews were conducted with all participants and analysed using thematic analysis.

Results

Patients recognised that empathic communication enhanced interactions, helping to engender a sense of trust in their clinician. They felt it was acceptable for GPs to convey optimism only if it was realistic, personalised, and embedded within an empathic consultation. Discussing patients’ experiences and views with them, and conveying an accurate understanding of these experiences improves the credibility of optimistic messages.

Conclusion

Patients value communication with empathy and optimism, but it requires a fine balance to ensure messages remain realistic and trustworthy. Increased use of a realistic optimistic approach within an empathic consultation could enhance consultations for OA and other chronic conditions, and improve patient outcomes. Digital training to help GPs implement these findings is being developed.

Effects of Patients' Expectation in Dermatology: Evidence from Experimental and Clinical Placebo Studies and Implications for Dermatologic Practice and Research

Patients' expectations towards the benefit of a treatment are key determinants of placebo responses and can affect the development and course of medical conditions and the efficacy and tolerability of active medical treatment. The mechanisms mediating these placebo and nocebo effects have been best described in the field of experimental pain and placebo analgesia. However, also in dermatology experimental and clinical studies demonstrate that various skin diseases such as inflammatory dermatoses and allergic reactions can be modulated by patients' expectations. Dermatologists should consider the important modulatory role of patients' expectations on the efficacy and tolerability of specific treatments and the key role of verbal information, patients' prior treatment experiences (associative learning), and the quality and quantity of doctor-patient communication in shaping treatment expectation. As a consequence, techniques aiming at maximizing patients' expectation effects should be implemented into daily clinical routine. By contrast, in clinical studies expectation effects should be maximally controlled and harmonized to improve the "assay sensitivity" to detect new compounds. Further translational studies, also in dermatoses that have not been investigated yet, are needed to better characterize the mechanisms underlying patients' expectation and to gain further insights into potential clinical implications of these effects in dermatologic conditions. Therefore, in this review, we provide a brief overview on the concept of expectation effects on treatment outcome in general, summarize what is already known about this topic for dermatologic diseases, and finally present the relevance of this topic in clinical dermatology.

Efficacy and Safety of Ibuprofen Plus Paracetamol in a Fixed-Dose Combination for Acute Postoperative Pain in Adults: Meta-Analysis and a Trial Sequential Analysis

BACKGROUND

Ibuprofen and paracetamol (acetaminophen) are very commonly used for analgesia and pain. In 2020, the US FDA gave its first approval of a fixed-dose combination (FDC) of the two drugs in the same tablet for postoperative pain. There has been no quantitative, summative analysis of the FDC effect size measures against postoperative pain in adults. Similar analyses exist, but only in pediatric patients.

OBJECTIVE

This was the first meta-analysis to compare the efficacy and safety outcomes of the ibuprofen/paracetamol FDC against placebo, administered postoperatively, for moderate to severe pain relief in adults.

METHODS

The MEDLINE, EMBASE, and Cochrane CENTRAL databases, in addition to the grey literature, were searched for clinical trials until April 2020, to identify comparative literature studies of the ibuprofen/paracetamol FDC in acute postoperative pain in adults. No restrictions on doses, formulations (oral, intravenous), and underlying type of surgery were applied. Independent reviewers performed the study selection, data extraction, and the risk-of-bias and quality-of-evidence assessments based on the Cochrane criteria. The outcome measures of interest in the meta-analysis were ≥ 50% pain relief , need for rescue medications, and occurrence of adverse drug events. Statistical analyses using a random-effects model were performed, at a statistical significance of p < 0.05. The RevMan software was used for analysis. A trial sequential analysis (TSA) was conducted to assess how precise and conclusive the meta-analysis outcomes are.

RESULTS

Seven double-blind, randomized controlled trials with 2947 participants were included. The FDC dose was at three different levels: 75-100 mg ibuprofen/250 mg paracetamol, 150-200 mg ibuprofen/500 mg paracetamol (FDA-approved dose level), and 292.5-400 mg ibuprofen/975-1000 mg paracetamol. The ≥ 50% pain relief outcome was more achieved with the FDC compared to placebo (risk ratio [RR] 2.60, 95% confidence interval [CI] 2.11-3.20, p < 0.00001), as was the reduced need for rescue medications (RR 0.51, 95% CI 0.37-0.71, p < 0.0001). While inconclusive based on TSA, the FDC was at the highest doses at least as well tolerated as placebo regarding the occurrence of adverse events, including severe, common, and treatment-related adverse events, as well as those that lead to discontinuation, but it was also significantly associated with lower rates of headache and nausea. Subgroup analyses confirmed that the efficacy and safety of the FDC were maintained regardless of doses and formulations. The sensitivity analysis confirmed outcomes against potential publication bias and identified sources of heterogeneity in analyses.

CONCLUSION

The ibuprofen plus paracetamol FDC is conclusively an effective analgesic against placebo in acute postoperative, moderate to severe pain in adults. It is also superiorly well tolerated, including at the higher dose of 292.5-400 mg ibuprofen/975-1000 mg paracetamol; however, safety outcomes were inconclusive. Future studies need to confirm the safety of FDC and its benefits against other marketed analgesics in postoperative pain.

Interpretation of chronic pain clinical trial outcomes: IMMPACT recommended considerations

Interpreting randomized clinical trials (RCTs) is crucial to making decisions regarding the use of analgesic treatments in clinical practice. In this article, we report on an Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) consensus meeting organized by the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks, the purpose of which was to recommend approaches that facilitate interpretation of analgesic RCTs. We review issues to consider when drawing conclusions from RCTs, as well as common methods for reporting RCT results and the limitations of each method. These issues include the type of trial, study design, statistical analysis methods, magnitude of the estimated beneficial and harmful effects and associated precision, availability of alternative treatments and their benefit-risk profile, clinical importance of the change from baseline both within and between groups, presentation of the outcome data, and the limitations of the approaches used.

Clinically Meaningful Reduction in Dyspareunia Is Associated With Significant Improvements in Health-Related Quality of Life Among Women With Moderate to Severe Pain Associated With Endometriosis: A Pooled Analysis of Two Phase III Trials of Elagolix

BACKGROUND

Dyspareunia experienced by women diagnosed with endometriosis is associated with a decreased health-related quality of life (HRQoL).

AIM

We evaluated the relationship of clinically meaningful improvements in dyspareunia with HRQoL changes among women with endometriosis.

METHODS

This was a post hoc analysis of pooled data from the phase III ELARIS-I and ELARIS-II clinical trials. Women aged 18-49 years with moderate to severe endometriosis-associated pain were randomized to placebo, elagolix 150 mg once daily, or elagolix 200 mg twice daily. HRQoL was measured using the validated Endometriosis Health Profile-30 questionnaire (EHP-30), consisting of 5 core domains and a sexual intercourse modular domain. Dyspareunia was ranked 0-3 (none, mild, moderate, or severe) or not applicable using a daily eDiary and averaged monthly. A woman with a clinically meaningful dyspareunia response (dyspareunia responder) was defined as a woman with a reduction from the baseline in dyspareunia score greater than or equal to a predetermined cutoff while maintaining stable/decreased analgesic use.

OUTCOMES

Dyspareunia response impact on EHP-30 scores was determined at 3 and 6 months using multivariate linear regression controlling for age, baseline EHP-30 scores, and dysmenorrhea and non-menstrual pelvic pain symptom severity.

RESULTS

Analysis included 1,368 women with a mean age of 32.2 years. Dyspareunia responders had significant improvements vs non-responders in all adjusted mean EHP-30 domain scores at months 3 and 6 (control and powerlessness: -17.8 and -18.5; emotional well-being: -10.0 and -10.4; pain: -15.3 and -15.7; self-image: -11.4 and -12.8; social support: -14.3 and -14.0; and sexual intercourse: -18.1 and -19.7; all P < .0001).

CLINICAL IMPLICATIONS

Dyspareunia improvements are associated with both personal and psychological benefits.

STRENGTHS & LIMITATIONS

This study involved a large sample of women from a well-defined patient population to provide statistical power in evaluating the results. As such, the findings may not be generalizable in a real-world setting. Although the perception of dyspareunia and its severity and the associated effect on HRQoL was subjective, the use of a large patient sample was used to minimize potential issues with this limitation.

CONCLUSION

Clinically meaningful responses in dyspareunia are associated with improvements across multiple HRQoL domains among women with endometriosis. Agarwal SK, Soliman AM, Pokrzywinski RM, et al. Clinically Meaningful Reduction in Dyspareunia Is Associated with Significant Improvements in Health-Related Quality of Life Among Women with Moderate to Severe Pain Associated with Endometriosis: A Pooled Analysis of Two Phase III Trials of Elagolix. J Sex Med 2020;17:2427-2433.

Placebo hypoalgesia: racial differences

No large-cohort studies that examine potential racial effects on placebo hypoalgesic effects exist. To fill this void, we studied placebo effects in healthy and chronic pain participants self-identified as either African American/black (AA/black) or white. We enrolled 372 study participants, 186 with a diagnosis of temporomandibular disorder (TMD) and 186 race-, sex-, and age-matched healthy participants to participate in a placebo experiment. Using a well-established paradigm of classical conditioning with verbal suggestions, each individual pain sensitivity was measured to calibrate the temperatures for high- and low-pain stimuli in the conditioning protocol. These 2 temperatures were then paired with a red and green screen, respectively, and participants were told that the analgesic intervention would activate during the green screens to reduce pain. Participants then rated the painfulness of each stimulus on a visual analog scale ranging from 0 to 100. Racial influences were tested on conditioning strength, reinforced expectations, and placebo hypoalgesia. We found that white participants reported greater conditioning effects, reinforced relief expectations, and placebo effects when compared with their AA/black counterparts. Racial effects on placebo were observed in TMD, although negligible, short-lasting, and mediated by conditioning strength. Secondary analyses on the effect of experimenter-participant race and sex concordance indicated that same experimenter-participant race induced greater placebo hypoalgesia in TMDs while different sex induced greater placebo hypoalgesia in healthy participants. This is the first and largest study to analyze racial effects on placebo hypoalgesia and has implications for both clinical research and treatment outcomes.

Certainty in ascending sensory signals - The unexplored driver of analgesic placebo response

Previous frameworks have failed to adequately explain the observed correlation between within-subject variability in pain reporting and analgesic placebo response. These relationships have been observed in both clinical and experimental setups. Within-subject variability of clinical pain scores is traditionally assessed based on daily pain diaries collected during the pre-intervention stage. Experimental variability can be assessed by the Focused Analgesia Selection Test (FAST), which calculates the relationship between noxious stimuli administrated at various intensities and pain reports. The variability, either clinical or experimental, has been shown to predict the placebo response. In explaining the placebo response, Bayesian Brain Hypothesis (BBH) posits that pain perception (posterior), is composed of certainty (precision) of expectations (priors due to belief or conditioning) and incoming sensory information (likelihood), with the bulk of research focused on the precision of priors. Virtually all placebo analgesia research has focused on the priors and their certainty, rather than on the certainty of the likelihood, mainly because it cannot be assessed directly. We propose that the within-subject variability, as encapsulated by the FAST, is a proxy for certainty in (or, precision of) ascending sensory signals, and our results suggest that it could not only be assessed, but also manipulated. If true, our hypothesis will facilitate new lines of research and could potentially promote precision analgesic medicine by use of variability of pain scores as a diagnostic method to identify pain patients who will benefit from specific treatments.

The evolution of temporomandibular disorders: A shift from experience to evidence

After over 80 years of much obsession as well as avoidance of the subject of temporomandibular disorders (TMDs), the dental profession is still divided over what they are and how to deal with them. Over this period, nearly every discipline in dentistry has played some role in the development of this field. Unfortunately, a significant amount of this information has been based on personal opinion, experience-based philosophies, or poorly conducted research. Furthermore, each dental specialty has been responsible for contributing to the concepts of the etiology and management of TMDs with their own professional bias; for example, orthodontists describe these problems in orthodontic terms and offer orthodontic treatments or solutions for their patients. As various treatment approaches were found to be effective at least some of the time, this has further led to misinformation and confusion within the profession. Advances in research from diverse fields, including neurophysiology, pain pathophysiology, genetics, endocrinology, behavioral sciences, and psychology, have significantly altered our understanding of TMDs and how they should be managed. The rigid mechanical and dental-based model of the past has been gradually replaced by a biopsychosocial medical model for the diagnosis and treatment of TMDs as well as other acute and chronic pain disorders. This paper discusses the evolution of our understanding of TMDs since they were first described 85 years ago. Contemporary scientific findings and their implications are presented in some detail for clinicians who wish to provide the appropriate management for their orofacial pain patients.

[Pain management at the emergency room reception desk]

Pain is the main complaint during an emergency room visit. Whether it is a reason in itself or associated with other symptoms, its management determines the proper course of care. They are also potentially a source of new pain, or added strain for the patient, relatives and caregivers. The nurse organizing the reception area prioritizes the passage of patients according to their potential seriousness. The pain assessment is part of this evaluation, renewed during the time of treatment with anticipated analgesia protocols.

Context matters: the psychoneurobiological determinants of placebo, nocebo and context-related effects in physiotherapy

Background

Placebo and nocebo effects embody psychoneurobiological phenomena where behavioural, neurophysiological, perceptive and cognitive changes occur during the therapeutic encounter in the healthcare context. Placebo effects are produced by a positive healthcare context; while nocebo effects are consequences of negative healthcare context. Historically, placebo, nocebo and context-related effects were considered as confounding elements for clinicians and researchers. In the last two decades this attitude started to change, and the understanding of the value of these effects has increased. Despite the growing interest, the knowledge and the awareness of using the healthcare context to trigger placebo and nocebo effects is currently limited and heterogeneous among physiotherapists, reducing their translational value in the physiotherapy field.

Objectives

To introduce the placebo, nocebo and context-related effects by: (1) presenting their psychological models; (2) describing their neurophysiological mechanisms; (3) underlining their impact for the physiotherapy profession; and (4) tracing lines for future researches.

Conclusion

Several psychological mechanisms are involved in placebo, nocebo and context-related effects; including expectation, learning processes (classical conditioning and observational learning), reinforced expectations, mindset and personality traits. The neurophysiological mechanisms mainly include the endogenous opioid, the endocannabinoid and the dopaminergic systems. Neuroimaging studies have identified different brain regions involved such as the dorsolateral prefrontal cortex, the rostral anterior cingulate cortex, the periaqueductal gray and the dorsal horn of spine. From a clinical perspective, the manipulation of the healthcare context with the best evidence-based therapy represents an opportunity to trigger placebo effects and to avoid nocebo effects respecting the ethical code of conduct. From a managerial perspective, stakeholders, organizations and governments should encourage the assessment of the healthcare context aimed to improve the quality of physiotherapy services. From an educational perspective, placebo and nocebo effects are professional topics that should be integrated in the university program of health and medical professions. From a research perspective, the control of placebo, nocebo and context-related effects offers to the scientific community the chance to better measure the impact of physiotherapy on different outcomes and in different conditions through primary studies.

Placebo effects in pain

Placebo effects influence symptom perceptions and treatment outcomes. Placebo effects can be explored in laboratory settings controlling for natural history and expectations. Such a mechanistic approach to neurological disorders has been implemented in the domain of chronic clinical pain and other neurological disorders. This article therefore focuses on definitions and historical notes related to placebo effects and mechanisms of placebo effects in chronic pain. Knowledge on mechanisms of placebo effects could inform current clinical practice for the treatment of neurological disorders by focusing on patients (and providers) expectations for outcome optimization.

Can taste be ergogenic?

Taste is a homeostatic function that conveys valuable information, such as energy density, readiness to eat, or toxicity of foodstuffs. Taste is not limited to the oral cavity but affects multiple physiological systems. In this review, we outline the ergogenic potential of substances that impart bitter, sweet, hot and cold tastes administered prior to and during exercise performance and whether the ergogenic benefits of taste are attributable to the placebo effect. Carbohydrate mouth rinsing seemingly improves endurance performance, along with a potentially ergogenic effect of oral exposure to both bitter tastants and caffeine although subsequent ingestion of bitter mouth rinses is likely required to enhance performance. Hot and cold tastes may prove beneficial in circumstances where athletes' thermal state may be challenged. Efficacy is not limited to taste, but extends to the stimulation of targeted receptors in the oral cavity and throughout the digestive tract, relaying signals pertaining to energy availability and temperature to appropriate neural centres. Dose, frequency and timing of tastant application likely require personalisation to be most effective, and can be enhanced or confounded by factors that relate to the placebo effect, highlighting taste as a critical factor in designing and administering applied sports science interventions.

Influence of placebo analgesia in pharmacological treatment of pain

Placebo effects are relevant to routine clinical practice, even if no traditional placebo is given. The healthcare encounter is often rich in factors that may affect both placebo and nocebo components of care, therefore, an opportunity exists to target elements of this encounter to enhance clinical effectiveness. This review will outline the contemporary conceptualizations of placebo and the mechanisms of placebo effects. Specifically, how to harness these placebo effects in clinical practice. Currently, these include optimizing the therapeutic context, shaping of expectations, assessing belief structures and framing information delivery, utilization of conditioning regimes to augment drug response or reduce overall drug dosing and the potential integration of traditional placebos with scientifically proven treatments to augment care.

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

Successfully predicting the susceptibility of individuals to placebo analgesics will aid in developing more effective pain medication and therapies, as well as aiding potential future clinical use of placebos. In pursuit of this goal, we analyzed healthy and chronic pain patients' patterns of responsiveness during conditioning rounds and their links to conditioned placebo analgesia and the mediating effect of expectation on those responses. We recruited 579 participants (380 healthy, 199 with temporomandibular disorder [TMD]) to participate in a laboratory placebo experiment. Individual pain sensitivity dictated the temperatures used for high- and low-pain stimuli, paired with red or green screens, respectively, and participants were told there would be an analgesic intervention paired with the green screens. Over two conditioning sessions and one testing session, participants rated the painfulness of each stimulus on a visual analogue scale from 0 to 100. During the testing phase, the same temperature was used for both red and green screens to assess responses to the placebo effect, which was defined as the difference between the average of the high-pain-cue stimuli and low-pain-cue stimuli. Delta scores, defined as each low-pain rating subtracted from its corresponding high-pain rating, served as a means of modeling patterns of conditioning strength and placebo responsiveness. Latent class analysis (LCA) was then conducted to classify the participants based on the trajectories of the delta values during the conditioning rounds. Classes characterized by persistently greater or increasing delta scores during conditioning displayed greater placebo analgesia during testing than those with persistently lower or decreasing delta scores. Furthermore, the identified groups' expectation of pain relief acted as a mediator for individual placebo analgesic effects. This study is the first to use LCA to discern the relationship between patterns of learning and the resultant placebo analgesia in chronic pain patients. In clinical settings, this knowledge can be used to enhance clinical pain outcomes, as chronic pain patients with greater prior experiences of pain reduction may benefit more from placebo analgesia.

Classical conditioning of antidepressant placebo effects in mice

INTRODUCTION

Placebo effects in human clinical trials for depression treatment are robust and often comparable to drug effects. Placebo effects are traditionally difficult to study in rodents due to the slow-onset action of classical antidepressant drugs. We hypothesized that the rapid antidepressant actions of ketamine would allow modeling antidepressant placebo effects in rodents.

METHODS

Male and female CD-1 mice received either ketamine or saline injections with concomitant exposure to specific environmental conditioning stimuli, for a total of three drug/conditioning sessions each 2 weeks apart. Two weeks later, during an evocation phase, mice were exposed to the drug-paired conditioning stimuli or no conditioned stimuli followed by testing for motor stimulatory actions and antidepressant-like effects using the forced swim test. Negative (no ketamine administration at any time) and positive (acute ketamine administration prior to evocation testing) control groups were included as comparators.

RESULTS

Both male and female mice exhibited increased locomotor activity following ketamine administration during the conditioning phase, which was not observed following exposure to the conditioning stimuli. Exposure to the conditioning stimuli previously paired with ketamine, similar to an acute ketamine administration, reduced immobility time in the forced swim test both 1 and 24 h after administration in male, but not female, mice.

CONCLUSIONS

These results represent the first evidence of antidepressant-like placebo-conditioned effects in an animal model. The developed approach can be used as a model to explore the neurobiological mechanisms of placebo effects, their possible sexually dimorphic effects, and relevance to mechanisms underlying antidepressant action.

Prior Therapeutic Experiences, Not Expectation Ratings, Predict Placebo Effects: An Experimental Study in Chronic Pain and Healthy Participants

INTRODUCTION

Many clinical trials fail because of placebo responses. Prior therapeutic experiences and patients' expectations may affect the capacity to respond to placebos in chronic disorders.

OBJECTIVE

The scope of this study in 763 chronic orofacial pain and healthy study participants was to compare the magnitude and prevalence of placebo effects and determine the putative role of prior therapeutic experiences vs. expectations.

METHODS

We tested placebo propensity in a laboratory setting by using 2 distinct levels of individually tailored painful stimulations (high pain and low pain) to reinforce expectations and provide a hypoalgesic experience (conditioning phase). Afterwards, both levels of pain were surreptitiously set at a moderate pain level to test for placebo effects (testing phase). Pain and expectation ratings were assessed as primary outcomes using visual analog scales.

RESULTS

In both chronic pain and healthy participants, placebo effects were similar in magnitude, with the larger prevalence of responders in the healthy participants. Although chronic pain participants reported higher pain relief expectations, expectations did not account for the occurrence of placebo effects. Rather, prior experience via conditioning strength mediated placebo effects in both pain and healthy participants.

CONCLUSIONS

These findings indicate that participants with chronic pain conditions display robust placebo effects that are not mediated by expectations but are instead directly linked to prior therapeutic experiences. This confirms the importance of assessing the therapeutic history while raising questions about the utility of expectation ratings. Future research is needed to enhance prediction of responses to placebos, which will ultimately improve clinical trial designs.

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

INTRODUCTION

Physicians and other prescribing clinicians use opioids as the primary method of pain management after traumatic injury, despite growing recognition of the major risks associated with usage for chronic pain. Placebos given after repeated administration of active treatments can acquire medication-like effects based on learning mechanisms. This study hypothesises that dose-extending placebos can be an effective treatment in relieving clinical acute pain in trauma patients who take opioids.

METHODS AND ANALYSIS

The relieving acute pain is a proof-of-concept randomised, placebo-controlled, double-blinded, single-site study enrolling 159 participants aged from 18 to 65 years with one or more traumatic injuries treated with opioids. Participants will be randomly assigned to three different arms. Arm 1 will receive the full dose of opioids with non-steroidal anti-inflammatory drugs (NSAIDs). Arm 2 will receive the 50% overall reduction in opioid dosage, dose-extending placebos and NSAIDs. Arm 3 (control) will receive NSAIDs and placebos. The trial length will be 3 days of hospitalisation (phase I) and 2-week, 1-month, 3-month and 6-month follow-ups (exploratory phase II). Primary and secondary outcomes include feasibility and acceptability of the study. Pain intensity, functional pain, emotional distress, rates of rescue therapy requests and patient-initiated medication denials will be collected.

ETHICS AND DISSEMINATION

All activities associated with this protocol are conducted in full compliance with the Institutional Review Board policies and federal regulations. Publishing this study protocol will enable researchers and funding bodies to stay up to date in their fields by providing exposure to research activity that may not otherwise be widely publicised.

DATE AND PROTOCOL VERSION IDENTIFIER

3/6/2019 (HP-00078742).

TRIAL REGISTRATION NUMBER

NCT03426137.

When Expectancies Are Violated: A Functional Magnetic Resonance Imaging Study

Positive and negative expectancies drive behavioral and neurobiological placebo and nocebo effects, which in turn can have profound effects on patient improvement or worsening. However, expectations of events and outcomes are often not met in daily life and clinical practice. It is currently unknown how this affects placebo and nocebo effects. We have demonstrated that the violation of expectancies, such as when there is a discrepancy between what is expected and what is actually presented, reduces both placebo and nocebo effects while causing an extinction of placebo effects. The reduction of placebo and nocebo effects was paralleled by an activation of the left inferior parietal cortex, a brain region that redirects attention when discrepancies between sensory and cognitive events occur. Our findings highlight the importance of expectancy violation in shaping placebo and nocebo effects and open up new avenues for managing positive and negative expectations in clinical trials and practices.

OPRM1 rs1799971, COMT rs4680, and FAAH rs324420 genes interact with placebo procedures to induce hypoalgesia

Genetics studies on the placebo hypoalgesic effect highlight a promising link between single nucleotide polymorphisms (SNPs) in the dopamine, opioid, and endocannabinoid genes and placebo hypoalgesia. However, epistasis and replication studies are missing. In this study, we expanded on previous findings related to the 3 SNPs in the opioid receptor mu subunit (OPRM1 rs1799971), catechol-O-methyltransferase (COMT rs4680), and fatty acid amide hydrolase (FAAH rs324420) genes associated with placebo hypoalgesia and tested the effect of a 3-way interaction on placebo hypoalgesia. Using 2 well-established placebo procedures (verbal suggestion and learning paradigm), we induced significant placebo hypoalgesic effects in 160 healthy participants. We found that individuals with OPRM1 AA combined with FAAH Pro/Pro and those carrying COMT met/met together with FAAH Pro/Pro showed significant placebo effects. Participants with COMT met/val alleles showed significant placebo effects independently of OPRM1 and FAAH allele combinations. Finally, the model that included the placebo procedure and genotypes predicted placebo responsiveness with a higher accuracy (area under the curve, AUC = 0.773) as compared to the SNPs alone indicating that genetic variants can only partially explain the placebo responder status. Our results suggest that the endogenous mu-opioid system with a larger activation in response to pain in the met/val allele carriers as well as the synergism between endogenous mu-opioid system and cannabinoids might play the most relevant role in driving hypoalgesic responses. Future epistasis studies with larger sample sizes will help us to fully understand the complexity of placebo effects and explain the mechanisms that underlie placebo responsiveness.

In search of a rodent model of placebo analgesia in chronic orofacial neuropathic pain

All treatments are given in a context, suggesting that conditioning cues may significantly influence therapeutic outcomes. We tested the hypothesis that context affects placebo analgesia in rodents. To produce neuropathic pain in rats, we performed chronic constriction injury of the infraorbital nerve. We then treated the rats daily, over a seven day period, with injections of either fentanyl or saline, with or without associated conditioning cues; a fourth group received no treatment. On the eighth day, we replaced fentanyl with saline to test for conditioned placebo analgesia. We tested the effects of treatment by measuring sensitivity to mechanical stimuli and grimace scale scores. We found no significant differences in either of these outcomes among the four experimental groups. These findings suggest that chronic, neuropathic pain in rats may not be susceptible to placebo analgesia.

Randomized Placebo-/Sham-Controlled Trials of Spinal Cord Stimulation: A Systematic Review and Methodological Appraisal

OBJECTIVES

The recent availability of paraesthesia/sensation free spinal cord stimulation (SCS) modalities allow the design of clinical trials of SCS using placebo/sham controls and blinding of patients, clinicians, and researchers. The aims of this study were to: 1) systematically review the current evidence base of randomized controlled trials (RCTs) of SCS placebo/sham trials and 2) to undertake a methodological critique of their methods. Based on this critique, we developed a checklist for the design and reporting of future RCTs of SCS.

MATERIALS AND METHODS

Electronic data bases were searched from inception until January 2019 for RCTs of SCS using a placebo/sham control. RCTs with only an active comparator arm were excluded. The results are presented as a narrative synthesis.

RESULTS

Searches identified 12 eligible RCTs. SCS modalities included paraesthesia stimulation, subthreshold, burst, and high-frequency SCS and were mainly conducted in patients with failed back surgery syndrome, complex regional pain syndrome, and refractory angina. The quality and transparency of reporting of the methods of placebo stimulation, blinding of patients, clinicians, and researchers varied markedly across studies.

CONCLUSIONS

To date the methods of placebo/sham control and blinding in RCTs have been poorly reported, leading to concerns about the validity and replicability of the findings. Important aspects that need to be clearly reported in the design of placebo-/sham-controlled RCTs of SCS include the transparent reporting of stimulation programming parameters, patient position during perception threshold measurement, management of the patient handheld programmer, frequency of recharging, and assessment of the fidelity of blinding.

Open-label dose-extending placebos for opioid use disorder: a protocol for a randomised controlled clinical trial with methadone treatment

INTRODUCTION

More than 2 million individuals in the USA have an opioid use disorder (OUD). Methadone maintenance treatment is the gold standard of medication-based treatment for OUD, but high-dose methadone is associated with cardiotoxicity and respiratory complications, among other side effects. These adverse effects make enhancing the effectiveness of lower doses of methadone an attractive therapeutic goal. Long recognised for its capacity to enhance treatment outcomes for a wide range of neuropsychiatric disorders including pain, the placebo effect offers an as-yet untested avenue to such an enhancement. This approach is particularly compelling given that individuals with substance use disorder tend to have higher salience attribution and may thereby be more sensitive to placebo effects. Our study combines two promising clinical methodologies-conditioning/dose-extension and open-label placebo-to investigate whether placebo effects can increase the effective potency of methadone in treatment-seeking OUD patients.

METHODS AND ANALYSIS

A total of 120 newly enrolled treatment-seeking OUD patients will be randomly assigned to one of two different groups: either methadone plus daily placebo dose-extension (PDE; treatment group) or methadone/treatment as usual (control). Participants will meet with study team members five times over the course of 3 months of treatment with methadone (baseline, 2 weeks, and 1, 2 and 3 months postbaseline). Throughout this study time period, methadone dosages will be adjusted by an addiction clinician blind to patient assignment, per standard clinical methods. The primary outcome is methadone dose at 3 months. Secondary outcomes include self-report of drug use; 3-month urine toxicology screen results; and treatment retention. Exploratory outcomes include several environmental as well as personality factors associated with OUD and with propensity to demonstrate a placebo effect.

ETHICS AND DISSEMINATION

Human subjects oversight for this study is provided by the University of Maryland, Baltimore and University of Maryland, College Park Institutional Review Boards. Additionally, the study protocol is reviewed annually by an independent Data and Safety Monitoring Board. Study results will be disseminated via research conference presentations and peer-reviewed publications.

TRIAL REGISTRATION NUMBER

NCT02941809.

The impact of contextual factors on nursing outcomes and the role of placebo/nocebo effects: a discussion paper

INTRODUCTION

Placebo and nocebo effects represent one of the most fascinating topics in the health care field.

OBJECTIVES

the aims of this discussion paper were (1) to briefly introduce the placebo and nocebo effects, (2) to elucidate the contextual factors able to trigger placebo and nocebo effects in the nursing field, and (3) to debate the impact of contextual factors on nursing education, practice, organisation, and research.

METHODS

a narrative review was conducted based on the available evidence.

RESULTS

Placebo responses (from Latin "I shall please") are a beneficial outcome(s) triggered by a positive context. The opposite are the nocebo effects (from Latin "I shall harm"), which indicates an undesirable outcome(s) caused by a negative context. Both are complex and distinct psychoneurobiological phenomena in which behavioural and neurophysiological changes arise subsequent to an interaction between the patient and the health care context.

CONCLUSION

Placebo and nocebo concepts have been recently introduced in the nursing discipline, generating a wide debate on ethical issues; however, the impact on nursing education, clinical practice, nursing administration, and research regarding contextual factors triggering nocebo and placebo effects has not been debated to date.

Introduction to the Theme “New Therapeutic Targets”

“New Therapeutic Targets” is the theme of articles in the Annual Review of Pharmacology and Toxicology, Volume 59. Reviews in this volume discuss targets for a variety of conditions in need of new therapies, including type 2 diabetes, heart failure with preserved ejection fraction, obesity, thyroid-associated ophthalmopathy, tinnitus, multiple sclerosis, Parkinson's disease and other neurodegenerative diseases, pain, depression, post-traumatic stress disorder, muscle wasting diseases, cancer, and anemia associated with chronic renal disease. Numerous articles in this volume focus on the identification, validation, and utility of novel therapeutic targets, in particular, ones that involve new or unexpected molecular entities. This theme complements several previous themes, including “New Approaches for Studying Drug and Toxicant Action: Applications to Drug Discovery and Development,” “Precision Medicine and Prediction in Pharmacology,” and “New Methods and Novel Therapeutic Approaches in Pharmacology and Toxicology.”