Placebo response in pain, fatigue, and performance: Possible implications for neuromuscular disorders

The impact of patients' pre-treatment expectations on immunosuppressive treatment outcomes in myasthenia gravis: A pilot correlational study

INTRODUCTION/AIMS

The impact of treatment expectations on active treatment outcomes has not been specifically investigated in neuromuscular disorders. We thus explored in myasthenia gravis (MG) the contribution of patients' pre-treatment expectations combined with an immunosuppressant drug on treatment outcomes.

METHODS

This pilot correlational study involved 17 patients with generalized MG, scheduled to start immunosuppressant azathioprine. At baseline, a healthcare professional administered: (i) the Stanford Expectations of Treatment Scale; (ii) a structured checklist paper form asking patients which side-effects they expected to develop after starting azathioprine, coupled with a standardized framing of statements. Quantitative Myasthenia Gravis (QMG) score and daily dose of concomitant drugs were assessed by neurologists as clinical outcomes. Clinical outcomes and side-effects were re-assessed at 3 and 6 months, and clinical outcomes were monitored at 18 months.

RESULTS

Clinically significant improvement in the QMG scores was achieved at 3 or 6 months. The level of state anxiety appeared to act as moderator of pre-treatment negative expectations (strong, positive, indicative correlation, rs = .733, p = .001). The latter were, in turn, associated with the fulfillment of side-effects that patients expected to develop with the new treatment (moderate, positive, indicative correlation, rs = .699, p = .002). No significant correlation emerged between positive and negative expectations.

DISCUSSION

Our findings show a very quick clinical response and also suggest that patients' expectations and anxiety contributed to treatment outcomes, highlighting the importance of promoting safety messages and education strategies around newly introduced treatments. Future goals include evaluating a larger cohort that includes a matched control group.

One spinal manipulation session reduces local pain sensitivity but does not affect postural stability in individuals with chronic low back pain: a randomised, placebo-controlled trial

BACKGROUND

Clinical practice guidelines recommend spinal manipulation for patients with low back pain. However, the effects of spinal manipulation have contradictory findings compared to placebo intervention. Therefore, this study investigated the immediate effects of lumbar spinal manipulation on pressure pain threshold (PPT) and postural stability in people with chronic low back pain (cLBP). Second, we investigated the immediate effect of lumbar spinal manipulation on pain intensity and the interference of the participant beliefs about which treatment was received in the PPT, postural stability, and pain intensity.

METHODS

A two-arm, randomised, placebo-controlled, double-blind trial was performed. Eighty participants with nonspecific cLPB and a minimum score of 3 on the Numeric Pain Rating Scale received one session of lumbar spinal manipulation (n = 40) or simulated lumbar spinal manipulation (n = 40). Primary outcomes were local and remote PPTs and postural stability. Secondary outcomes were pain intensity and participant's perceived treatment allocation. Between-group mean differences and their 95% confidence intervals (CIs) estimated the treatment effect. One-way analysis of covariance (ANCOVA) was performed to assess whether beliefs about which treatment was received influenced the outcomes.

RESULTS

Participants had a mean (SD) age of 34.9 (10.5) years, and 50 (62.5%) were women. Right L5 [between-group mean difference = 0.55 (95%CI 0.19 to 0.90)], left L5 [between-group mean difference = 0.45 (95%CI 0.13 to 0.76)], right L1 [between-group mean difference = 0.41 (95%CI 0.05 to 0.78)], left L1 [between-group mean difference = 0.57 (95%CI 0.15 to 0.99)], left DT [between-group mean difference = 0.35 (95%CI 0.04 to 0.65)], and right LE [between-group mean difference = 0.34 (95%CI 0.08 to 0.60)] showed superior treatment effect in the spinal manipulation group than sham. Neither intervention altered postural stability. Self-reported pain intensity showed clinically significant decreases in both groups after the intervention. A higher proportion of participants in the spinal manipulation group achieved more than two points of pain relief (spinal manipulation = 90%; sham = 60%). The participants' perceived treatment allocation did not affect the outcomes.

CONCLUSION

One spinal manipulation session reduces lumbar pain sensitivity but does not affect postural stability compared to a sham session in individuals with cLPB. Self-reported pain intensity lowered in both groups and a higher proportion of participants in the spinal manipulation group reached clinically significant pain relief. The participant's belief in receiving the manipulation did not appear to have influenced the outcomes since the adjusted model revealed similar findings.

Placebo and nocebo responses in painful diabetic neuropathy: systematic review and meta-analysis

ABSTRACT

This preregistered (CRD42021223379) systematic review and meta-analysis aimed to characterize the placebo and nocebo responses in placebo-controlled randomized clinical trials (RCTs) on painful diabetic neuropathy (PDN), updating the previous literature by a decade. Four databases were searched for PDN trials published in the past 20 years, testing oral medications, adopting a parallel-group design. Magnitude of placebo or nocebo responses, Cochrane risk of bias, heterogeneity, and moderators were evaluated. Searches identified 21 studies (2425 placebo-treated patients). The overall mean pooled placebo response was -1.54 change in the pain intensity from baseline [95% confidence interval (CI): -1.52, -1.56, I 2 = 72], with a moderate effect size (Cohen d = 0.72). The pooled placebo 50% response rate was 25% [95% CI: 22, 29, I 2 = 50%]. The overall percentage of patients with adverse events (AEs) in the placebo arms was 53.3% [95% CI: 50.9, 55.7], with 5.1% [95% CI: 4.2, 6] of patients dropping out due to AEs. The year of study initiation was the only significant moderator of placebo response (regression coefficient = -0.06, [95% CI: -0.10, -0.02, P = 0.007]). More recent RCTs tended to be longer, bigger, and to include older patients (N = 21, rs = 0.455, P = 0.038, rs = 0.600, P = 0.004, rs = 0.472, P = 0.031, respectively). Our findings confirm the magnitude of placebo and nocebo responses, identify the year of study initiation as the only significant moderator of placebo response, draw attention to contextual factors such as confidence in PDN treatments, patients' previous negative experiences, intervention duration, and information provided to patients before enrollment.

Placebo and nocebo effects and mechanisms associated with pharmacological interventions: an umbrella review

OBJECTIVES

This review aimed to summarise the existing knowledge about placebo and nocebo effects associated with pharmacological interventions and their mechanisms.

DESIGN

Umbrella review, adopting the Assessment of Multiple Systematic Reviews 2 tool for critical appraisal.

DATA SOURCES

MEDLINE/PubMed, Scopus, Web of Science, PsycINFO, Cochrane Central Register of Controlled Trial were searched in September 2022, without any time restriction, for systematic reviews, narrative reviews, original articles. Results were summarised through narrative synthesis, tables, 95% CI.

OUTCOME MEASURES

Mechanisms underlying placebo/nocebo effects and/or their effect sizes.

RESULTS

The databases search identified 372 studies, for a total of 158 312 participants, comprising 41 systematic reviews, 312 narrative reviews and 19 original articles. Seventy-three per cent of the examined systematic reviews were of high quality.Our findings revealed that mechanisms underlying placebo and/or nocebo effects have been characterised, at least in part, for: pain, non-noxious somatic sensation, Parkinson's disease, migraine, sleep disorders, intellectual disability, depression, anxiety, dementia, addiction, gynaecological disorders, attention-deficit hyperactivity disorder, immune and endocrine systems, cardiovascular and respiratory systems, gastrointestinal disorders, skin diseases, influenza and related vaccines, oncology, obesity, physical and cognitive performance. Their magnitude ranged from 0.08 to 2.01 (95% CI 0.37 to 0.89) for placebo effects and from 0.32 to 0.90 (95% CI 0.24 to 1.00) for nocebo effects.

CONCLUSIONS

This study provides a valuable tool for clinicians and researchers, identifying both results ready for clinical practice and gaps to address in the near future.

FUNDING

Università Cattolica del Sacro Cuore, Milan, Italy with the 'Finanziamento Ponte 2022' grant.

PROSPERO REGISTRATION NUMBER

CRD42023392281.

Placebo and Nocebo Effects as Bayesian-Brain Phenomena: The Overlooked Role of Likelihood and Attention

The Bayesian-brain framework applied to placebo responses and other mind-body interactions suggests that the effects on the body result from the interaction between priors, such as expectations and learning, and likelihood, such as somatosensorial information. Significant research in this area focuses on the role of the priors, but the relevance of the likelihood has been surprisingly overlooked. One way of manipulating the relevance of the likelihood is by paying attention to sensorial information. We suggest that attention can influence both precision and position (i.e., the relative distance from the priors) of the likelihood by focusing on specific components of the somatosensorial information. Two forms of attention seem particularly relevant in this framework: mindful attention and selective attention. Attention has the potential to be considered a "major player" in placebo/nocebo research, together with expectations and learning. In terms of application, relying on attentional strategies as "amplifiers" or "silencers" of sensorial information could lead to an active involvement of individuals in shaping their care process and health. In this contribution, we discuss the theoretical implications of these intuitions with the aim to provide a comprehensive framework that includes Bayesian brain, placebo/nocebo effects, and the role of attention in mind-body interactions.

Efficacy of Intravesical Botulinum Toxin A Injection in the Treatment of Refractory Overactive Bladder in Children

This study aimed to evaluate the efficacy of intravesical botulinum toxin A (BoNT-A) injections for the treatment of pediatric overactive bladder (OAB) by exploring the differential treatment outcomes in children with different OAB etiologies and those who received additional intrasphincteric BoNT-A injections. We performed a retrospective review of all pediatric patients who received intravesical BoNT-A injections between January 2002 and December 2021. All patients underwent a urodynamic study at baseline and three months after BoNT-A administration. A Global Response Assessment (GRA) score of ≥2 at three months after BoNT-A injection was defined as successful treatment. Fifteen pediatric patients (median age, 11 years), including six boys and nine girls, were enrolled in the study. A statistically significant decrease in detrusor pressure from baseline to three months postoperatively was observed. Thirteen (86.7%) patients reported successful results (GRA ≥ 2). The cause of OAB and additional intrasphincteric BoNT-A injections did not affect the improvement in urodynamic parameters and treatment success. The study demonstrated that intravesical BoNT-A injection is effective and safe for the treatment of neurogenic and non-neurogenic OAB in children refractory to conventional therapies. Additionally, intrasphincteric BoNT-A injections do not provide additional benefits in the treatment of pediatric OAB.

Proportion attributable to contextual effects in general medicine: a meta-epidemiological study based on Cochrane reviews

OBJECTIVES

Our objectives were to examine the magnitude of the proportion attributable to contextual effects (PCE), which shows what proportion of the treatment arm response can be achieved by the placebo arm across various interventions, and to examine PCE variability by outcome type and condition.

DESIGN

We conducted a meta-epidemiological study.

SETTING

We searched the Cochrane Database of Systematic Reviews with the keyword 'placebo' in titles, abstracts and keywords on 1 January 2020.

PARTICIPANTS

We included reviews that showed statistically significant beneficial effects of the intervention over placebo for the first primary outcome.

MAIN OUTCOME MEASURES

We performed a random-effects meta-analysis to calculate PCEs based on the pooled result of each included review, grouped by outcome type and condition. The PCE quantifies how much of the observed treatment response can be achieved by the contextual effects.

PUBLIC AND PATIENT INVOLVEMENT STATEMENT

No patient or member of the public was involved in conducting this research.

RESULTS

We included 328 out of 3175 Cochrane systematic reviews. The results of meta-analyses showed that PCEs varied greatly depending on outcome type (I²=98%) or condition (I²=98%), but mostly lie between 0.40 and 0.95. Overall, the PCEs were 0.65 (95% CI 0.59 to 0.72) on average. Subjective outcomes were 0.50 (95% CI 0.41 to 0.59), which was significantly smaller than those of semiobjective (PCE 0.78; 95% CI 0.72 to 0.85) or objective outcomes (PCE 0.94; 95% CI 0.91 to 0.97).

CONCLUSIONS

The results suggest that much of the observed benefit is not just due to the specific effect of the interventions. The specific effects of interventions may be larger for subjective outcomes than for objective or semiobjective outcomes. However, PCEs were exceptionally variable. When we evaluate the magnitude of PCEs, we should consider each PCE individually, for each condition, intervention and outcome in its context, to assess the importance of an intervention for each specific clinical setting.

The relationship between dietary patterns and sleep disorders in shift workers

BACKGROUND: Few studies have been done on the association of dietary intakes with sleep disorders among shift workers, in particular those exposed to air pollution. OBJECTIVE: We aimed to investigate the association of major dietary patterns with risk of sleep disorders in shift workers of a cement factory. METHODS: This cross-sectional study was carried out on 257 male shift workers in a cement factory in Iran. Usual dietary intake of participants was assessed using a validated self-administrated 147-item dish-based food frequency questionnaire. To examine sleep disturbances of participants, we used the Epworth Sleepiness Scale. RESULTS: Three major dietary patterns including Classic Iranian, Modern Iranian, and High Protein Low Fruit and vegetables were identified. The Classic Iranian pattern was mainly consisted of high-protein animal foods, fruit, and vegetables, while the Modern Iranian pattern had high amounts of refined grains, solid oils, and caffeine drinks. No significant association was found between adherence to the Classic Iranian pattern and risk of sleep disorders (OR: 2.33; 95% CI: 0.69, 7.81) and also for the Modern Iranian dietary pattern (OR: 0.62; 95% CI: 0.20, 1.93). However, we found a significant direct association between the High Protein Low Fruit and vegetables dietary pattern and risk of sleep disorders (OR: 3.92; 95% CI: 1.03, 14.86). CONCLUSIONS: This study showed a significant direct association between a dietary pattern high in animal proteins and solid oils and low in fruit and vegetables with risk of sleep disorders among shift workers in the cement factory. However, no such association was found for the two other dietary patterns.

Transcranial direct current stimulation of 3 cortical targets is no more effective than placebo as treatment for fibromyalgia: a double-blind sham-controlled clinical trial

ABSTRACT

Transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) and the dorsolateral prefrontal cortex seem to improve pain and other symptoms of fibromyalgia (FM), although the evidence on the effectiveness of tDCS and the optimal stimulation target is not robust enough. Our main objective was to establish the optimal area of stimulation, comparing the 2 classical targets and a novel pain-related area, the operculo-insular cortex, in a sham-controlled trial. Using a double-blind design, we randomly assigned 130 women with FM to 4 treatment groups (M1, dorsolateral prefrontal cortex, operculo-insular cortex, and sham), each receiving fifteen 20-minute sessions of 2 mA anodal tDCS over the left hemisphere. Our primary outcome was pain intensity. The secondary outcomes were the other core symptoms of FM (fatigue, mood, cognitive and sleep disorders, and hyperalgesia measured by the pressure pain threshold). We performed the assessment at 3 time points (before, immediately after treatment, and at 6 months follow-up). The linear mixed-model analysis of variances showed significant treatment effects across time for clinical pain and for fatigue, cognitive and sleep disturbances, and experimental pain, irrespective of the group. In mood, the 3 active tDCS groups showed a significantly larger improvement in anxiety and depression than sham. Our findings provide evidence of a placebo effect, support the use of tDCS for the treatment of affective symptoms, and challenge the effectiveness of tDCS as treatment of FM.

Consideration in Randomized Placebo-Controlled Trial on Neck Pain to Avoid the Placebo Effect in Analgesic Action

Background: In neck pain treatment, many therapies are focused on etiology, while it is well-known that placebo analgesia is also present in these therapies. The specific efficacy for etiology may be underestimated by ignoring their actual placebo effect. In this study, a logistic regression analysis is used to explore the risk factors causing different placebo responses in patients with neck pain among two RCTs. The probability of the placebo effect is predicted based on these risk factors.

Methods: Trial A and Trial B were similarly designed, randomized, double-/single-blind, placebo-controlled trials in patients treating neck pain with Qishe pill or Shi-style manipulation. Both studies set a placebo pill twice a day or traction for every other day as control. For further analyses on the placebo effect in neck pain management, logistic regression was used to assess subgroup-placebo interactions. The odds ratio assessed a significant influence on the placebo effect.

Results: In this pooled analysis, the total number of patients recruited for these two studies was 284, of which 162 patients received placebo treatment (placebo drug or traction for every other day). No statistically significant differences are found at baseline between the participants with placebo effect and non-placebo effect in the gender, age, and disease duration except in VAS and NDI at the initial time. There are numerically more patients with placebo effect in the shorter disease duration subgroup (< 4 months [76%]), higher initial VAS subgroup (>60 mm [90%]), and worse initial NDI subgroup (>24 [72%]) compared with the gender and age subgroup. An ROC curve is established to assess the model-data fit, which shows an area under the curve of 0.755 and a 95% confidence interval of 0.677–0.830. Participants who show placebo effect after 2 weeks have significantly lower VAS scores after 4 weeks, while there is no significant difference in NDI improvement between the two groups after 4 weeks.

Conclusion: Neck pain patients with shorter disease duration are more likely to overscore their pain severity, because of their less experience in pain perception, tolerance, and analgesia expectation.

Perceived Consumption of a High-Dose Caffeine Drink Delays Neuromuscular Fatigue

ABSTRACT

Elhaj, HM, Imam, O, Page, BW, Vitale, JM, and Malek, MH. Perceived consumption of a high-dose caffeine drink delays neuromuscular fatigue. J Strength Cond Res 36(5): 1185-1190, 2022-The placebo effect is a concept in which a desired outcome arises, mainly from the belief that the treatment (i.e., supplement or drug) was beneficial although no active ingredient was given. The results of studies related to the placebo effect primarily examine functional performance. What remains unanswered, however, is whether these changes in performance are associated with neuromuscular alterations in the exercised muscles. The purpose of the study, therefore, was to determine the influence of the placebo effect on the physical working capacity fatigue threshold (PWCFT) for a continuous exercise paradigm. To achieve this aim, subjects were told that they were participating in a study to determine the dosage response (low or high) of caffeine on neuromuscular fatigue when in fact no caffeine was given during the experiment. We hypothesized that the perceived consumption of the high-dose caffeine drink would result in a higher PWCFT than the perceived consumption of the low-dose caffeine drink and placebo. Secondarily, we hypothesized that the perceived consumption of the high-dose caffeine drink would result in a higher power output than the perceived consumption of the placebo. Nine healthy college-aged men (mean ± SEM: age, 25.7 ± 1.3 years; body mass, 84.4 ± 3.1 kg; and height: 1.82 ± 0.02 m) volunteered to be in the study. For each of the visits, subjects were given an 8 oz. bottle of water with dissolved crystal light. After the drink was consumed, subjects rested in the laboratory for 1 hour before performing the incremental single-leg knee-extensor ergometry. Immediately after the termination of the incremental single-leg knee-extensor ergometry, the subject was asked which caffeine dose (placebo, low, or high) they believed they consumed for that visit. There were no significant mean differences for maximal power output for the 3 perceived conditions (placebo: 62 ± 3, low-dose caffeine: 62 ± 4, and high-dose caffeine: 65 ± 3 W). When the subjects perceived consuming the high-dose caffeine drink, there were significant mean differences (all p-values < 0.01), for PWCFT, between the other conditions (mean ± SEM: placebo: 23 ± 3 W, low-dose caffeine: 26 ± 2 W, and high-dose caffeine: 42 ± 3 W). This corresponded to a significant mean difference (all p-values < 0.01) when the PWCFT was presented as a percentage of the maximal power output (mean ± SEM: placebo: 37 ± 5%, low-dose caffeine: 42 ± 3%, and high-dose caffeine: 64 ± 3%). The application of our results may indicate that the subject's expectancy, to caffeine consumption, plays a critical role in delaying the onset of neuromuscular fatigue despite not receiving any caffeine in their drinks.

What is the role of placebo in neurotherapeutics?

INTRODUCTION

The widespread use of the word 'placebo' in the medical literature emphasizes the importance of this phenomenon in modern biomedical sciences. Neuroscientific research over the past thirty years shows that placebo effects are genuine psychobiological events attributable to the overall therapeutic context, and can be robust in both laboratory and clinical settings.

AREAS COVERED

Here the authors describe the biological mechanisms and the clinical implications of placebo effects with particular emphasis on neurology and psychiatry, for example in pain, movement disorders, depression. In these conditions, a number of endogenous systems have been identified, such as endogenous opioids, endocannabinoids, and dopamine, which contribute to the placebo-induced benefit.

EXPERT OPINION

Every effort should be made to maximize the placebo effect and reduce its evil twin, the nocebo effect, in medical practice. This does not require the administration of a placebo, but rather the enhancement of the effects of pharmacological and nonpharmacological treatments through a good doctor-patient interaction.

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.

Understanding Symptoms in RYR1-Related Myopathies: A Mixed-Methods Analysis Based on Participants' Experience

BACKGROUND

In rare diseases such as ryanodine receptor 1-related myopathies (RYR1-RM), health-related quality of life (HRQoL) measures are critically important so clinicians and researchers can better understand what symptoms are most important to participants, with the ultimate goal of finding tangible solutions for them.

OBJECTIVES

The main objective of this study was to characterize symptoms in individuals with RYR1-RM to inform future research. A secondary objective of this study was to analyze positive and negative sentiments regarding symptoms and treatment effects post N-acetylcysteine (NAC) administration in individuals with RYR1-RM.

METHODS

The study used a mixed-methods design applying methodological triangulation. Qualitative data were collected via semi-structured interviews at three visits to characterize symptoms in individuals with RYR1-RM and to analyze treatment effects. Qualitative data were then transformed into quantitative results to measure the frequency with which each symptom was mentioned by participants.

RESULTS

A total of 12 symptoms were identified as areas of interest to participants with RYR1-RM, highlighting fatigue and weakness as key symptoms. Data transformation categorized more than 1000 citations, reporting a greater number of positive comments for postintervention interviews than for baseline and preintervention visits and that NAC group participants stated more positive comments regarding treatment effect than did the placebo group.

CONCLUSIONS

We present a comprehensive characterization of symptoms in RYR1-RM and how those symptoms influence HRQoL. Furthermore, the introduction of mixed methods may be a valuable way to better understand patient-centered data in rare diseases to support affected individuals in coping with their symptoms.

Examining the Relationship Between Patient Fatigue-Related Symptom Clusters and Carer Depressive Symptoms in Advanced Cancer Dyads: A Secondary Analysis of a Large Hospice Data Set

BACKGROUND

Most symptom management takes place in the community, conducted by patient and/or informal carer dyads with guidance from clinicians. Given the prevalence of cancer, there is a critical need for examination of the impact of managing multiple symptoms, particularly those that cluster with fatigue, on informal carers.

OBJECTIVES

To (1) examine clustering of patient fatigue-related symptom severity and distress in individuals with cancer and (2) test the hypothesis that patient fatigue-related symptom clusters (severity, distress) will be positively associated with carer depressive symptoms.

METHODS

Secondary analysis of 689 hospice patient/informal carer dyads using exploratory factor analysis and structural equation modeling. Patient symptoms were measured by the Memorial Symptom Assessment Scale, and carer depressive symptoms were measured by the Center for Epidemiological Study-Depression Scale.

RESULTS

Patients were 73 (SD, 12) years old, and 43% were female. Carers were 65 years (SD, 14) years old, and 74% were female. For symptom severity, dyspnea, dry mouth, lack of appetite, drowsiness, cough, dizziness, and difficulty swallowing clustered with fatigue. For symptom distress, dyspnea, cough, and dry mouth clustered with fatigue. Structural equation modeling results indicated that the patient fatigue severity cluster was positively related to carer depressive symptoms (b = 0.12, P < .05), but distress was not.

CONCLUSION

Managing multiple symptoms that cluster with fatigue negatively impacts informal carers.

IMPLICATIONS FOR PRACTICE

When patients complain of severe fatigue, clinicians need to explore all causes and ask about other symptoms while exploring whether the informal carer is feeling burdened or depressed.

The subthalamic nucleus and the placebo effect in Parkinson's disease

The study of the placebo effect, or response, is related to the investigation of the psychologic component of different therapeutic rituals. The high rate of placebo responses in Parkinson's disease clinical trials provided the impetus for investigating the underlying mechanisms. Ruling out spontaneous remission and regression to the mean through the appropriate experimental designs, genuine psychologic placebo effects have been identified, in which both patients' expectations of therapeutic benefit and learning processes are involved. Specifically, placebo effects are associated with dopamine release in the striatum and changes in neuronal activity in the subthalamic nucleus, substantia nigra pars reticulata, and motor thalamus in Parkinson's disease, as assessed through positron emission tomography and single-neuron recording during deep brain stimulation, respectively. Conversely, verbal suggestions of clinical worsening or drug dose reduction induce nocebo responses in Parkinson's disease, which have been detected at both behavioral and electrophysiologic level. Important implications and applications emerge from this new knowledge. These include better clinical trial designs, whereby patients' expectations should always be assessed, as well as better drug dosage in order to reduce drug intake.

Assessment of Placebo Response in Objective and Subjective Outcome Measures in Rheumatoid Arthritis Clinical Trials

Importance

Large placebo responses in randomized clinical trials may keep effective medication from reaching the market. Primary outcome measures of clinical trials have shifted from patient-reported to objective outcomes, partly because response to randomized placebo treatment is thought to be greater in subjective compared with objective outcomes. However, a direct comparison of placebo response in subjective and objective outcomes in the same patient population is missing.

Objective

To assess whether subjective patient-reported (pain severity) and objective inflammation (C-reactive protein [CRP] level and erythrocyte sedimentation rate [ESR]) outcomes differ in placebo response.

Design, Setting, and Participants

The placebo arms of 5 double-blind, randomized, placebo-controlled clinical trials were included in this cross-sectional study. These trials were conducted internationally for 24 weeks or longer between 2005 and 2009. All patients with rheumatoid arthritis randomized to placebo (N = 788) were included. Analysis of data from these trials was conducted from March 27 to December 31, 2019.

Intervention

Placebo injection.

Main Outcomes and Measures

The difference (with 95% CIs) from baseline at week 12 and week 24 on a 0- to 100-mm visual analog scale to evaluate the severity of pain, CRP level, and ESR.

Results

Of the 788 patients included in the analysis, 644 were women (82%); mean (SD) age was 51 (13) years. There was a statistically significant decrease in patient-reported pain intensity (week 12: -14 mm; 95% CI, -12 to -16 mm and week 24: -20 mm; 95% CI, -16 to -22 mm). Similarly, significant decreases were noted in the CRP level (week 12: -0.51 mg/dL; 95% CI, -0.47 to -0.56 mg/dL and week 24: -1.16 mg/dL; 95% CI, -1.03 to -1.30 mg/dL) and ESR (week 12: -11 mm/h; 95% CI, -10 to 12 mm/h and week 24: -25 mm/h; 95% CI, -12 to -26 mm/h) (all P < .001).

Conclusions and Relevance

The findings of this study suggest that improvements in clinical outcomes among participants randomized to placebo were not limited to subjective outcomes. Even if these findings could largely demonstrate a regression to the mean, they should be considered for future trial design, as unexpected favorable placebo responses may result in a well-designed trial becoming underpowered to detect the treatment difference needed in clinical drug development.

Can insights from placebo and nocebo mechanisms studies improve the randomized controlled trial?

Background and aims The randomized controlled trial (RCT) is currently facing several challenges, one of these being that the placebo response appears to be increasing in RCTs, thereby making it difficult to demonstrate an effect of potentially new treatments over placebo. This problem has primarily been approached by predicting the magnitude of the placebo response via stable factors, such as demographic variables, and/or by developing complex designs aimed at reducing the placebo response in the hope that it will improve the test of the active treatment. Yet, the success of this approach has so far been limited. Methods A new approach toward improving the RCT is put forward based on placebo and nocebo mechanism studies, i.e. studies that investigate the mechanisms underlying placebo analgesia and nocebo hyperalgesia. In a series of meta-analyses the magnitude of placebo and nocebo effects were determined. Experimental studies across nociplastic and neuropathic pain conditions and across pharmacological and acupuncture treatments investigated psychological and neurobiological mechanisms underlying these effects. The obtained results were used to make approximations of expectations to see if that could predict the placebo response in RCTs and function as a new way of tapping into the placebo component of treatment effects. Results The magnitude of placebo and nocebo effects is large and highly variable. Placebo effects exist across chronic pain conditions with varying degrees of known etiology as well as across pharmacological and non-pharmacological treatments. Patients' perception of the treatment, the verbal suggestions given for pain relief, and the patients' expectations toward pain relief contribute to the magnitude of the placebo effect and to pain relief following placebo interventions. Also, unintentional unblinding and patients' perception of a treatment markedly influence the treatment outcome. By making approximations of expectations toward treatment effects it was possible to predict the magnitude of the placebo response in RCTs. Conclusions and implications The new approach of tapping into or directly asking patients about their perception and expectations toward a treatment, along with the account of the natural history of pain, has the potential to improve the information that can be obtained from RCTs. Thus, by interfacing insights from placebo and nocebo mechanism studies, it may be possible to enhance the information that can be obtained from RCTs and to account for a large part of the variability in the placebo component of the overall treatment effect. This approach has the potential to improve the scientific evaluation of treatments, as well as to illustrate how the effect of treatments can be optimized in clinical practice, which is the crux of evidence-based medicine.

Placebo Effects in the Neuroendocrine System: Conditioning of the Oxytocin Responses

OBJECTIVE

There is evidence that placebo effects may influence hormone secretion. However, few studies have examined placebo effects in the endocrine system, including oxytocin placebo effects. We studied whether it is possible to trigger oxytocin placebo effects using a classical conditioning paradigm.

METHODS

Ninety-nine women were assigned to a conditioned, control, or drug control group. In the two-phase conditioning paradigm, participants in the conditioned and drug control groups received an oxytocin nasal spray combined with a distinctive smell (conditioned stimulus [CS]) for three acquisition days, whereas the control group received placebo spray. Subsequently, the conditioned and control groups received placebo spray with the CS and the drug control group received oxytocin spray for three evocation days. Salivary oxytocin was measured several times during each day. Pain sensitivity and facial evaluation tests previously used in oxytocin research were also administered.

RESULTS

On evocation day 1, in the conditioned group, oxytocin significantly increased from baseline to 5 minutes after CS (B[slope] = 19.55, SE = 5.88, p < .001) and remained increased from 5 to 20 (B = -10.42, SE = 5.81, p = .071) and 50 minutes (B = -0.70, SE = 3.37, p = .84). On evocation day 2, a trend for increase in oxytocin was found at 5 minutes (B = 15.22, SE = 8.14, p = .062). No placebo effect was found on evocation day 3 (B = 3.57, SE = 3.26, p = .28). Neither exogenous nor conditioned oxytocin affected pain or facial tasks.

CONCLUSIONS

Results indicate that oxytocin release can be conditioned and that this response extinguishes over time. Triggering hormonal release by placebo manipulation offers various clinical possibilities, such as enhancing effects of pharmacological treatments or reducing dosages of medications.

TRIAL REGISTRATION

The study was registered as a clinical trial on www.trialregister.nl (number NTR5596).

Pain, placebo, and test of treatment efficacy: a narrative review

Over the past decade, the mechanisms underlying placebo effects have begun to be identified. At the same time, the placebo response appears to have increased in pharmacological trials and marked placebo effects are found in neurostimulation and surgical trials, thereby posing the question whether non-pharmacological interventions should be placebo-controlled to a greater extent. In this narrative review we discuss how the knowledge of placebo mechanisms may help to improve placebo control in pharmacological and non-pharmacological trials. We review the psychological, neurobiological, and genetic mechanisms underlying placebo analgesia and outline the current problems and potential solutions to the challenges with placebo control in trials on pharmacological, neurostimulation, and surgical interventions. We particularly focus on how patients' perception of the therapeutic intervention, and their expectations towards treatment efficacy may help develop more precise placebo controls and blinding procedures and account for the contribution of placebo factors to the efficacy of active treatments. Finally, we discuss how systematic investigations into placebo mechanisms across various pain conditions and types of treatment are needed in order to 'personalise' the placebo control to the specific pathophysiology and interventions, which may ultimately lead to identification of more effective treatment for pain patients. In conclusion this review shows that it is important to understand how patients' perception and expectations influence the efficacy of active and placebo treatments in order to improve the test of new treatments. Importantly, this applies not only to assessment of drug efficacy but also to non-pharmacological trials on surgeries and stimulation procedures.

How May Placebo Mechanisms Influence Orofacial Neuropathic Pain?

The conceptualization of placebo has changed from inactive pills to a detailed understanding of how patients' perception of receiving a treatment influences pain processing and overall treatment outcome. Large placebo effects were recently demonstrated in chronic neuropathic pain, thereby opening the question of whether placebo effects also apply to orofacial neuropathic pain. In this article, we review the new definitions, magnitude, and social, psychological, neurobiologic, and genetic mechanisms of placebo effects in pain, especially neuropathic pain, to illustrate that placebo effects are not simply response bias but psychoneurobiological phenomena that can be measured at many levels of the neuroaxis. We use this knowledge to carefully illustrate how patients' perceptions of the treatment, the relationship with the health care provider, and the expectations and emotions toward a treatment can influence test and treatment outcome and potentially skew the results if they are not taken into consideration. Orofacial neuropathic pain is a new research area, and we review the status on definition, diagnosis, mechanisms, and pharmacologic treatment of neuropathic pain after trigeminal nerve injury, as this condition may be especially influenced by placebo factors. Finally, we have a detailed discussion of how knowledge of placebo mechanisms may help improve the understanding, diagnosis, and treatment of orofacial neuropathic pain, and we illustrate pitfalls and opportunities of applying this knowledge to the test of dental treatments.

The placebo response in myasthenia gravis assessed by quantitative myasthenia gravis score: A meta-analysis

INTRODUCTION

This meta-analysis investigates the placebo response in generalized myasthenia gravis (MG) trials by means of Quantitative Myasthenia Gravis (QMG) scores.

METHODS

PubMed, Scopus, Web of Science, Cochrane Controlled Trial Register, and EMBASE were searched. QMG score, dropouts rate, adverse events (AEs), and AEs responsible for dropouts were examined, together with treatment moderators.

RESULTS

The magnitude of placebo response showed an effect size of 0.24, which was significantly lower than 0.67 of the drug response (P = 0.019). Furthermore, the forest plot revealed that, overall, active treatments showed a significantly higher impact on QMG scores than placebos.

CONCLUSIONS

Placebo and drug responses in MG trials are small and moderate, respectively. The lack of MG trials with a pure placebo arm or a no-treatment control arm made it impossible to disentangle improvements due to the placebo psychological effect from other effects such as natural history and/or regression to the mean. Muscle Nerve 59:671-678, 2019.

The placebo effect in the motor domain is differently modulated by the external and internal focus of attention

Among the cognitive strategies that can facilitate motor performance in sport and physical practice, a prominent role is played by the direction of the focus of attention and the placebo effect. Consistent evidence converges in indicating that these two cognitive functions can influence the motor outcome, although no study up-to-now tried to study them together in the motor domain. In this explorative study, we combine for the first time these approaches, by applying a placebo procedure to increase force and by manipulating the focus of attention with explicit verbal instructions. Sixty healthy volunteers were asked to perform abduction movements with the index finger as strongly as possible against a piston and attention could be directed either toward the movements of the finger (internal focus, IF) or toward the movements of the piston (external focus, EF). Participants were randomized in 4 groups: two groups underwent a placebo procedure (Placebo-IF and Placebo-EF), in which an inert treatment was applied on the finger with verbal information on its positive effects on force; two groups underwent a control procedure (Control-IF and Control-EF), in which the same treatment was applied with overt information about its inefficacy. The placebo groups were conditioned about the effects of the treatment with a surreptitious amplification of a visual feedback signalling the level of force. During the whole procedure, we recorded actual force, subjective variables and electromyography from the hand muscles. The Placebo-IF group had higher force levels after the procedure than before, whereas the Placebo-EF group had a decrease of force. Electromyography showed that the Placebo-IF group increased the muscle units recruitment without changing the firing rate. These findings show for the first time that the placebo effect in motor performance can be influenced by the subject’s attentional focus, being enhanced with the internal focus of attention.

The Role of Patient-Practitioner Relationships in Placebo and Nocebo Phenomena

INTRODUCTION

Placebo and nocebo effects form part of all therapeutic environments and play a significant role in the effectiveness of treatment outcomes. Patient expectancies drive these phenomena, which can be shaped through contextual factors including verbal suggestions, conditioning, and social observation.

OBJECTIVES

This review seeks to identify the biopsychosocial factors of the patient-practitioner interaction that play a role in the development of placebo and nocebo effects, as well as the anthropological elements of the biodynamic process of relating that are meaningful in the development of expectancies.

METHODS

We conducted a narrative review of frameworks of the placebo and nocebo effect, including the impact of expectancies and interpersonal relationships in the context of healing and the clinical setting.

RESULTS

Expectancies leading to placebo and nocebo effects can be modified by macro and micro factors, such as culture and society, as well as individual psychobiological traits, respectively. The developmental sociobiological adaptations that form and consolidate mindsets and meaningful contexts play an important role in shaping patient expectancies, as well as patients' conscious and subconscious reactions to signs and actions taking place within the clinical environment. Practitioner characteristics, like empathy, friendliness, and competence, favor the formation of positive expectancies. Caring and warm patient-practitioner interactions can enhance the therapeutic value of clinical encounters when patients' positive expectancies are actively encouraged and engaged.

CONCLUSION

A patient-centered approach rooted in demonstrating care and empathy can positively enhance a patient's experience within the clinical environment and activate psychosociobiological adaptations associated with the placebo phenomenon. Pain patients could particularly benefit from non-invasive approaches for improving treatment effectiveness and quality-of-life.

Clinical relevance of contextual factors as triggers of placebo and nocebo effects in musculoskeletal pain

Placebo and nocebo effects are embodied psycho-neurobiological responses capable of modulating pain and producing changes at different neurobiological, body at perceptual and cognitive levels. These modifications are triggered by different contextual factors (CFs) presented in the therapeutic encounter between patient and healthcare providers, such as healing rituals and signs. The CFs directly impact on the quality of the therapeutic outcome: a positive context, that is a context characterized by the presence of positive CFs, can reduce pain by producing placebo effects, while a negative context, characterized by the presence of negative CFs, can aggravate pain by creating nocebo effects. Despite the increasing interest about this topic; the detailed study of CFs as triggers of placebo and nocebo effects is still lacked in the management of musculoskeletal pain.

Increasing evidence suggest a relevant role of CFs in musculoskeletal pain management. CFs are a complex sets of internal, external or relational elements encompassing: patient’s expectation, history, baseline characteristics; clinician’s behavior, belief, verbal suggestions and therapeutic touch; positive therapeutic encounter, patient-centered approach and social learning; overt therapy, posology of intervention, modality of treatment administration; marketing features of treatment and health care setting. Different explanatory models such as classical conditioning and expectancy can explain how CFs trigger placebo and nocebo effects. CFs act through specific neural networks and neurotransmitters that were described as mediators of placebo and nocebo effects.

Available findings suggest a relevant clinical role and impact of CFs. They should be integrated in the clinical reasoning to increase the number of treatment solutions, boosts their efficacy and improve the quality of the decision-making. From a clinical perspective, the mindful manipulation of CFs represents a useful opportunity to enrich a well-established therapy in therapeutic setting within the ethical border. From a translational perspective, there is a strong need of research studies on CFs close to routine and real-world clinical practice in order to underline the uncertainty of therapy action and help clinicians to implement knowledge in daily practice.

Why We should Assess Patients' Expectations in Clinical Trials

Most of the analgesic clinical trials have failed to succeed over the past years because of the occurrence of large placebo responses. Patients' expectations about the therapeutic benefit represent a major determinant of the placebo response. Therefore, assessing patients' expectations should become the rule in any clinical trial. This would allow us to better interpret therapeutic outcomes when comparing placebo and verum groups.