Conscious expectation and unconscious conditioning in analgesic, motor, and hormonal placebo/nocebo responses

Preserving the placebo effect after disclosure: A new perspective on non-deceptive placebos

The present study explores whether a particular style of placebo disclosure could serve as a tool to foster a renewed trust in one's own inherent resources and elicit a meaningful placebo effect. In a motor performance task, two placebo groups received inert transcutaneous electrical nerve stimulation (TENS) in each of four sessions along with information on its force-enhancing properties. Before the final session, one of the placebo groups was informed about the placebo, which was portrayed as a means to unleash an inherent potential. Along with force, we systematically monitored task-specific self-efficacy to test whether this variable would be differentially modulated in the two placebo groups. Compared to two control groups, placebo groups showed higher force and self-efficacy in the last session. No differences in self-efficacy were observed in the placebo groups even after revealing the placebo procedure, suggesting that the disclosure was effective in 'safeguarding' individuals' self-efficacy. These findings may have important implications, paving the way for the use of placebos that not only are ethically permissible but also support individuals' self-efficacy.

The Placebo Effect in Exercise and Mental Health Research

This chapter describes the placebo effect in the context of physical activity and mental health. Following a brief historical overview, definitions for placebos, placebo effects, and related terminology are discussed. Next, three major methodological challenges posed from studying the placebo effect in the context of exercise are described. Additionally, the role of a primary psychological mechanism of placebo and nocebo effects - expectations - will be summarized through the lens of key terminology. Findings from relevant chronic and acute exercise studies that have measured or manipulated exercise-associated expectations will be presented. The chapter concludes with recommendations for controlling or quantifying the placebo effect in exercise and mental health research and its implications in clinical practice.

Factors associated with a placebo effect in Parkinson's disease in clinical trials: a meta-analysis

OBJECTIVES

Outcomes of clinical trials of treatment in patients with Parkinson's disease (PD) may be influenced by placebo effects. The aim of this study was to determine the factors associated with placebo effects in Parkinson's disease (PD) for guidance with design of future clinical trials.

METHODS

Factors associated with placebo effects in PD were examined in a meta-analysis using a random effects model with pooling of placebo effects on the Unified Parkinson's Disease Rating Scale part III (UPDRS III) or Movement Disorder Society sponsored revision of UPDRS III (MDS-UPDRS III). The following prespecified variables were included in the analyses: with or without drug at baseline, with or without a placebo run-in phase, with or without motor fluctuation, published year, number of study sites, placebo administration period, age, sex, disease duration, and daily levodopa dose. Publication bias was assessed by visual inspection of funnel plots and adjusted using the trim-and-fill method.

RESULTS

Thirty-eight articles with a total of 4828 subjects satisfied the inclusion criteria. There was a significant placebo effect using UPDRS III or MDS-UPDRS III (SMD = - 0.25; 95% CI - 0.35 to - 0.14; p < 0.001, I2 = 92%). Subgroup and/or multivariate meta-regression analyses revealed that placebo effects were associated with advanced PD (p = 0.04), drug exposure at baseline (p < 0.001), placebo administration period (p < 0.001), and disease duration (p < 0.01).

CONCLUSIONS

The results of this study are important as guidance in design of future clinical trials in which the influence of placebo effects is minimized.

Could Relationship-Based Learnt Beliefs and Expectations Contribute to Physiological Vulnerability of Chronic Pain? Making a Case to Consider Attachment in Pain Research

Pain is an interpersonal and inherently social experience. Pain perception and administration of medical treatment all occur in a particular environmental and social context. Early environmental influences and early learning experiences and interactions condition the body's response to different threats (like pain), ultimately shaping the underlying neurophysiology. These early interactions and experiences also determine what situations are perceived as threatening, as well as our belief in our own ability to self-manage, and our belief in others to offer support, during perceived threats. These beliefs intrinsically drive the combination of behaviors that emerge in response to perceived threats, including pain. Such behaviors can be categorized into attachment styles. In this interdisciplinary review, we synthesize and summarize evidence from the neurobiological, psychobiological, psychosocial, and psychobehavioral fields, to describe how these beliefs are embedded in the brain's prediction models to generate a series of expectations/perceptions around the level of safety/threat in different contexts. As such, these beliefs may predict how one experiences and responds to pain, with potentially significant implications for the development and management of chronic pain. Little attention has been directed to the effect of adult attachment style on pain in research studies and in the clinical setting. Using interdisciplinary evidence, we argue why we think this interaction merits further consideration and research. PERSPECTIVE: This review explores the influence of attachment styles on pain perception, suggesting a link between social connections and chronic pain development. It aligns with recent calls to emphasize the social context in pain research and advocates for increased focus on adult attachment styles in research and clinical practice.

Impact of cardiac rehabilitation on erectile dysfunction in cardiovascular patients: a systematic review and meta-analysis

Background

Cardiovascular diseases (CVDs) and erectile dysfunction (ED) frequently co-occur, significantly affecting the quality of life of individuals.

Aim

To assess the impact of cardiac rehabilitation (CR) on ED in patients with CVD through a systematic review and meta-analysis.

Methods

This study analyzed randomized controlled trials and other studies comparing CR with usual care for adult males (≥18 years) with any cardiac disease. Literature searches were extensive, and the risk of bias was evaluated by the Cochrane Collaboration tool. Data from 6 studies involving 668 participants were included in the meta-analysis.

Outcomes

The primary outcome was the improvement in ED, as measured with the International Index of Erectile Function.

Results

A statistically significant improvement in erectile function was observed across 6 studies, with a Morris dppc2 effect size of 0.38 (95% CI, 0.17-0.59). Despite initial high heterogeneity (I 2 = 95.7%), identification and correction for selective outcome reporting bias mitigated this issue.

Clinical Translation

CR has a modest but statistically significant impact on improving ED in patients with CVD, indicating its potential positive contribution to the quality of life of this group.

Strengths and Limitations

The study's strengths include a comprehensive literature search and a rigorous methodological approach. Limitations involve high heterogeneity among studies and a low level of evidence due to small sample sizes and study quality; however, the source of heterogeneity was identified and mitigated following risk-of-bias assessment.

Conclusion

The results suggest that CR has a statistically significant but modest impact on improving ED in patients with CVD. Clinicians should consider the integration of CR into the clinical management of these individuals. This study underscores the potential for CR to contribute positively to the quality of life for patients with CVD by addressing associated ED (PROSPERO: CRD42022374625).

Nocebo expectations rather than placebo expectations affect topical pain relief: A randomized clinical trial

Patients' expectations and beliefs regarding the potential benefits and harms of medical interventions may induce placebo and nocebo effects, and affect the response to pain therapies. In a randomized clinical trial, we examined the effect of placebo and nocebo expectations on pain relief and adverse events (AEs) in association with a topical treatment among 65 cancer survivors experiencing chronic musculoskeletal pain. Participants received either a 1% camphor-based topical pain patch or a placebo treatment for 14 days. We measured pain severity with the worst pain item of the Brief Pain Inventory (BPI) at baseline and 14 days and treatment expectations at baseline with validated expectation questionnaires. We found that high vs. low nocebo expectations decreased pain severity improvements by 2.5 points (95% confidence interval [CI] -3.8 to -1.2; p<0.001) on a 0-10 numeric rating scale of the BPI and pain response rate by 42.7% (95% CI 0.2-0.6; p<0.001) at day 14, irrespective of placebo expectation status or treatment arms. Patients with high vs. low nocebo expectations in the true arm reported 22.4% more unwanted AEs. High nocebo expectations were associated with increased AEs by 39.5% (odds ratio: 12.0, 95% CI 1.2, 145.5; p=0.029) and decreased pain response in the true arm vs. placebo. Our study demonstrated that nocebo expectations, rather than placebo expectations, elevate the risk of AEs and compromise the effect of topical pain interventions. The findings raise the possibility that nocebo expectations may worsen somatic symptoms through heightening central pain amplification and should be further investigated.

Social Learning of Placebo Effects in Pain: A Critical Review of the Literature and a Proposed Revised Model

Relatively recently, in 2009, experimental studies were undertaken to determine the role of social observational learning in forming hypoalgesic, analgesic and hyperalgesic responses to a placebo. The research findings obtained in studies published before 2018 were integrated and formed the basis of the theoretical model of social learning of placebo effects in pain proposed by Bajcar and Bąbel. This model considered the involvement of different types of modeling (ie, behavioral modeling, symbolic modeling, and verbal modeling) in shaping placebo hypoalgesia/analgesia and nocebo hyperalgesia. The model assumed that pain expectancies might be involved in observationally induced placebo effects in pain and that the effectiveness of observational learning in shaping placebo effects could be moderated by the observer's dispositions, especially empathy. Based on the latest research data, we propose a modified and significantly extended version of this model. The revised model includes the involvement of particular types of modeling in placebo effects and their role in shaping conscious pain-related expectancies. It explains the role of dispositional empathy in shaping observationally induced placebo effects. Notably, the extended version of the model considers the contribution of the characteristics of the observed person to the magnitude of placebo effects induced by social learning. PERSPECTIVE: The paper proposes a comprehensive theoretical approach to explaining the role of observational learning in shaping placebo effects in pain. The proposed model emphasizes the potential of this form of learning in shaping placebo responses and indicates factors that can modify the effectiveness of observational learning.

Neuropsychological mechanisms of observational learning in human placebo effects

Scientific evidence indicates that placebo effects are psychoneurobiological events involving the contribution of distinct central nervous systems and peripheral physiological mechanisms that influence pain perception and other symptoms. Placebo effects can occur without formal conditioning and direct prior experience because crucial information can be acquired through observational learning. Observation of benefits in another person results in placebo effects of a magnitude like those induced by directly experiencing an analgesic benefit. Understanding the psychological mechanisms of observationally induced placebo effects is a complex and multifaceted endeavor. While previous reviews have highlighted various frameworks and models to understand these phenomena, the underlying biological mechanisms have been overlooked. We summarize critically current understanding of its behavioral and neural mechanisms. Understanding the neural mechanisms of hypoalgesia driven by observation can serve as a foundation for future development of novel theoretical and methodological approaches and ultimately, applications.

Pain Rating is Worth a Thousand Words: Nocebo Hyperalgesia Induced by Verbal Modeling Prevails Over the Effects of Symbolic Modeling and Verbal Suggestion

This study compares the effectiveness of verbal modeling, symbolic modeling, and verbal suggestion in inducing nocebo hyperalgesia. It is the first study to examine the contribution of stress to observationally induced nocebo hyperalgesia. This study's experimental groups represented various sources of social information: a group of people participating in the study (verbal modeling), a single participant (symbolic modeling), and an experimenter (verbal suggestion). During the experiment, participants received electrocutaneous stimuli at the same intensity, some of which were applied with a nocebo (sham device). Participants in the verbal modeling group were acquainted with pain ratings that had allegedly been provided by other participants. The ratings suggested that other participants experienced more pain in the nocebo trials than in the control trials. In the symbolic modeling group, participants observed a videotaped model experiencing more pain in the nocebo than in the control trials. In the verbal suggestion group, participants received a verbal suggestion of hyperalgesia in the nocebo trials and no suggestion in the control trials. No manipulations were used in the control group. To investigate whether nocebo hyperalgesia is stable over time, an additional extinction phase was conducted. Nocebo hyperalgesia was induced by verbal modeling only and was partially mediated by expectancy. Stress was a significant moderator of the induced effect. Nocebo hyperalgesia was extinguished during the extinction phase. The obtained results provide potential implications for minimizing nocebo hyperalgesia in clinical practice by, for instance, controlling patients' expectancies and stress levels. PERSPECTIVE: The study shows the role of pain-related information derived from other people in shaping negative treatment experiences in the individual. Because information from others has a particular impact on individuals experiencing stress, both this information and the stress level of patients should be monitored in the treatment process.

Creating Placebo Nonresponders in the Lab

Conditioning and expectation are known to be the main mechanisms of placebo analgesia. They may operate together, so that expectations may be enhanced by a conditioning procedure. Although most of the studies have tried to potentiate expectations through conditioning in order to generate good placebo responders, a few studies have tried to mismatch conditioning and expectations in order to investigate the subsequent administration of a placebo. In this study, we want to further investigate this mismatch. We generated incongruent associations during a conditioning procedure in which the study participants did not get what they expected. In fact, although the participants received verbal instructions of pain decrease following the administration of a placebo, we surreptitiously increased the painful electric stimulation. Two pairings of these incongruent associations (mismatch between what was expected and what was experienced) disrupted expectations of analgesia as well as the placebo effect, as assessed by measuring electric pain thresholds on the hand. The effects of mismatch conditioning on the hand extended to the contralateral arm and to a different type of pain (tourniquet), which suggests that local mismatch conditioning may affect the whole body. In all cases, expectations predicted placebo analgesia. These findings indicate that placebo nonresponders can be created in the laboratory by acting on expectations and that local effects can be generalized to other parts of the body. They also stress the importance of expectations in the therapeutic outcome, with important implications for clinical trials. PERSPECTIVE: By using mismatch conditioning, in which study participants did not get what they expected, we reduced expectations of analgesia, and this reduction abolished placebo analgesia. This effect extended to other parts of the body and other types of pain, which indicates that placebo nonresponders can be created in the laboratory.

The Nocebo Effect

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

Effects of deep brain stimulation and verbal suggestions on pain in Parkinson's disease

BACKGROUND AND OBJECTIVES

In Parkinson's disease (PD) patients, verbal suggestions have been shown to modulate motor and clinical outcomes in treatment with subthalamic deep brain stimulation (DBS). Furthermore, DBS may alleviate pain in PD. However, it is unknown if verbal suggestions influence DBS' effects on pain.

METHODS

Twenty-four people with PD and DBS had stimulation downregulated (80-60 to 20%) and upregulated (from 20-60 to 80%) in a blinded manner on randomized test days: (1) with negative and positive suggestions of pain for down- and upregulation, respectively, and (2) with no suggestions to effect (control). Effects of DBS and verbal suggestions were assessed on ongoing and evoked pain (hypertonic saline injections) via 0-10 numerical rating scales along with motor symptoms, expectations, and blinding.

RESULTS

Stimulation did not influence ongoing and evoked pain but influenced motor symptoms in the expected direction. Baseline and experimental pain measures showed no patterns in degree of pain. There was a trend toward negative suggestions increasing pain and positive suggestions decreasing pain. Results show significant differences in identical stimulation with negative vs positive suggestions (60% conditions AUC 38.75 vs 23.32, t(13) = 3.10, p < 0.001). Expectations to pain had small to moderate effects on evoked pain. Patients estimated stimulation level correctly within 10 points.

CONCLUSION

Stimulation does not seem to influence ongoing and evoked pain, but verbal suggestions may influence pain levels. Patients appear to be unblinded to stimulation level which is an important consideration for future studies testing DBS in an attempted blind fashion.

The Optimal Learning Cocktail for Placebo Analgesia: A Randomized Controlled Trial Comparing Individual and Combined Techniques

This study investigated for the first time the effects of individual and combined application of 3 learning techniques (verbal suggestions, classical conditioning, and observational learning) on placebo analgesia and extinction. Healthy participants (N = 206) were assigned to 8 different groups in which they were taught through either a verbal suggestion, a conditioning paradigm, a video observing someone, or any combination thereof that a placebo device (inactive transcutaneous electric nerve stimulation [TENS]) was capable of alleviating heat pain, whereas one group did not (control). Placebo analgesia was quantified as the within-group difference in experienced pain when the placebo device was (sham) 'activated' or 'inactivated' during equal pain stimuli, and compared between groups. Placebo analgesia was induced in groups with 2 or 3 learning techniques. Significantly stronger placebo analgesia was induced in the combination of all 3 learning techniques as compared to the individual learning techniques or control condition, underlining the additional contribution of 3 combined techniques. Extinction did not differ between groups. Furthermore, pain expectancies, but not state anxiety or trust, mediated placebo analgesia. Our findings emphasize the added value of combining 3 learning techniques to optimally shape expectancies that lead to placebo analgesia, which can be used in experimental and clinical settings. PERSPECTIVE: This unique experimental study compared the individual versus combined effects of 3 important ways of learning (verbal suggestions, classical conditioning, and observational learning) on expectation-based pain relief. The findings indicate that placebo effects occurring in clinical practice could be optimally strengthened if healthcare providers apply these techniques in combination.

The importance and limitations of polysomnography in insomnia disorder-a critical appraisal

The importance polysomnography (PSG) in the diagnosis and treatment process of insomnia disorder (ID) remains highly disputed. This review summarises the state of the science regarding PSG indications and findings in ID, and the indications to conduct PSG in ID as stated by relevant guidelines. It then highlights the most relevant questions regarding the topic, including the relevance of ID subtyping, to allow an individualised pharmacological or psychotherapeutic treatment approach.

Learning pain from others: a systematic review and meta-analysis of studies on placebo hypoalgesia and nocebo hyperalgesia induced by observational learning

ABSTRACT

Observing someone experience pain relief or exacerbation after an intervention may induce placebo hypoalgesia or nocebo hyperalgesia. Understanding the factors that contribute to these effects could help in the development of strategies for optimizing treatment of chronic pain conditions. We systematically reviewed and meta-analyzed the literature on placebo hypoalgesia and nocebo hyperalgesia induced by observational learning (OL). A systematic literature search was conducted in the databases PubMed, PsycINFO, Web of Science, ScienceDirect, PsycARTICLES, Scopus, and Academic Search Ultimate. Twenty-one studies were included in the systematic review, 17 of which were suitable for meta-analysis (18 experiments; n = 764 healthy individuals). The primary end point was the standardized mean difference (SMD) for pain following placebo cues associated during OL with low vs high pain. Observational learning had a small-to-medium effect on pain ratings (SMD 0.44; 95% confidence interval [CI] 0.21-0.68; P < 0.01) and a large effect on pain expectancy (SMD 1.11; 95% CI 0.49-2.04; P < 0.01). The type of observation (in-person vs videotaped) modulated the magnitude of placebo hypoalgesia/nocebo hyperalgesia ( P < 0.01), whereas placebo type did not ( P = 0.23). Finally, OL was more effective when observers' empathic concern (but no other empathy-related factors) was higher ( r = 0.14; 95% CI 0.01-0.27; P = 0.03). Overall, the meta-analysis demonstrates that OL can shape placebo hypoalgesia and nocebo hyperalgesia. More research is needed to identify predictors of these effects and to study them in clinical populations. In the future, OL could be an important tool to help maximize placebo hypoalgesia in clinical settings.

Nocebo Hyperalgesia in Patients With Fibromyalgia and Healthy Controls: An Experimental Investigation of Conditioning and Extinction Processes at Baseline and 1-Month Follow-up

Nocebo effects are adverse treatment outcomes that are not ascribed to active treatment components. Potentially, their magnitude might be higher in patients with chronic pain compared to healthy controls since patients likely experience treatment failure more frequently. The current study investigated group differences in the induction and extinction of nocebo effects on pressure pain at baseline (N = 69) and 1-month follow-up (N = 56) in female patients with fibromyalgia and matched healthy controls. Nocebo effects were first experimentally induced via classical conditioning combined with instructions on the pain-increasing function of a sham transcutaneous electrical nerve stimulation device, then decreased via extinction. One month later, the same procedures were repeated to explore their stability. Results suggest that nocebo effects were induced in the healthy control group during baseline and follow-up. In the patient group, nocebo effects were only induced during follow-up, without clear group differences. Extinction was only observed during baseline in the healthy control group. Further comparisons of nocebo effects and extinction indicated no significant changes across sessions, possibly suggesting their overall magnitudes were stable over time and across groups. In conclusion, contrary to our expectations, patients with fibromyalgia did not have stronger nocebo hyperalgesia; instead, they might be less responsive to nocebo manipulations than healthy controls. PERSPECTIVE: The current study is the first to investigate group differences in experimentally manipulated nocebo hyperalgesia between chronic pain and healthy populations at baseline and 1-month follow-up. Since nocebo effects are common in clinical settings, their investigation in different populations is essential to explain and minimize their adverse effects during treatment.

A new method for analyzing clinical trials in depression based on individual propensity to respond to placebo estimated using artificial intelligence

One of the major reasons for trial failures in major depressive disorders (MDD) is the presence of unpredictable levels of placebo response as the individual baseline propensity to respond to placebo is not adequately controlled by the current randomization and statistical methodologies. The individual propensity to respond to any treatment or intervention assessed at baseline was considered as a major non-specific prognostic and confounding effect. The objective of this paper was to apply the propensity score methodology to control for potential imbalance at baseline in the propensity to respond to placebo in clinical trials in MDD. Individual propensity was estimated using artificial intelligence (AI) applied to observations collected in two pre-randomization occasions. Cases study are presented using data from two randomized, placebo-controlled trials to evaluate the efficacy of paroxetine in MDD. AI models were used to estimate the individual propensity probability to show a treatment non-specific placebo effect. The inverse of the estimated probability was used as weight in the mixed-effects analysis to assess treatment effect. The comparison of the results obtained with and without propensity weight indicated that the weighted analysis provided an estimate of treatment effect and effect size significantly larger than the conventional analysis.

Learned Nocebo Effects on Cutaneous Sensations of Pain and Itch: A Systematic Review and Meta-analysis of Experimental Behavioral Studies on Healthy Humans

OBJECTIVE

In past decades, the field of nocebo research has focused on studying how sensory perception can be shaped by learning. Nocebo effects refer to aggravated sensory experiences or increased sensitivity to sensations such as pain and itch resulting from treatment-related negative experiences. Behavioral conditioning and verbal suggestions of a negative treatment outcome may aggravate pain and itch perception. Gaining a comprehensive view of the magnitude of nocebo effects and contributing factors will help steer nocebo research toward fruitful directions for understanding complex sensory phenomena.

METHODS

We conducted a systematic review and meta-analysis of a total of 37 distinct experimental nocebo studies on healthy participants (all published in English between 2008 and 2021), with four separate meta-analyses for nocebo effects on pain or itch. We conducted subgroup analyses and meta-regression on factors such as type and intensity of sensory stimuli, and length of conditioning paradigms.

RESULTS

This meta-analysis showed that, on average, effect sizes of nocebo effects were moderate to large (Hedges g between 0.26 and 0.71 for the four primary outcomes). The combination of conditioning and verbal suggestions yielded stronger nocebo responses on pain in particular. Subgroup analyses, including factors such as the type of sensory stimulation, did not explain the moderate heterogeneity in nocebo magnitudes between different studies. Risk of bias was generally low and was not related to nocebo magnitudes either.

CONCLUSIONS

We discuss these results in relation to the role of conditioning and aversive learning, and we recommend more consistency in designing and reporting nocebo experiments.

Artificial intelligence approach for the analysis of placebo-controlled clinical trials in major depressive disorders accounting for individual propensity to respond to placebo

Treatment effect in clinical trials for major depressive disorders (RCT) can be viewed as the resultant of treatment specific and non-specific effects. Baseline individual propensity to respond non-specifically to any treatment or intervention can be considered as a major non-specific confounding effect. The greater is the baseline propensity, the lower will be the chance to detect any treatment-specific effect. The statistical methodologies currently applied for analyzing RCTs doesn't account for potential unbalance in the allocation of subjects to treatment arms due to heterogenous distributions of propensity. Hence, the groups to be compared may be imbalanced, and thus incomparable. Propensity weighting methodology was used to reduce baseline imbalances between arms. A randomized, double-blind, placebo controlled, three arms, parallel group, 8-week, fixed-dose study to evaluate efficacy of paroxetine CR 12.5 and 25 mg/day is presented as a cases study. An artificial intelligence model was developed to predict placebo response at week 8 in subjects assigned to placebo arm using changes from screening to baseline of individual Hamilton Depression Rating Scale items. This model was used to predict the probability to respond to placebo in each subject. The inverse of the probability was used as weight in the mixed-effects model applied to assess treatment effect. The analysis with and without propensity weight indicated that the weighted analysis provided an estimate of treatment effect and effect-size about twice larger than the non-weighted analysis. Propensity weighting provides an unbiased strategy to account for heterogeneous and uncontrolled placebo effect making patients' data comparable across treatment arms.

Are there placebo or nocebo effects in balancing performance?

Placebo and nocebo effects could influence the perceived, actual, or both postural stabilities. Therefore, this experiment examined whether postural stability is susceptible to placebo and nocebo effects. Driven by expectations, these cognitions could influence the motor stability of people in physical rehabilitation and those with motion instability. We randomly assigned 78 participants to a placebo, nocebo, or control group. Then, we applied a sham sports cream with positive, negative, or neutral instructions about its impact on balance. Next, we tested postural stability with a modified version of the Modified Clinical Test of Sensory Interaction in Balance, including standard, proprioceptive, visual, and vestibular tests before and after the intervention. Further, we measured expected and perceived performance with visual analog scales and assessed trait anxiety, change in state anxiety, optimism, holistic thinking, persistence, and cooperation with questionnaires. The intervention did not affect actual test performances; similarly, trait and state variables and expectations did not have an impact. Furthermore, the experimental manipulation and trait and state variables did not significantly affect perceived performance. However, the association between expectation and perceived performance was strong (ϱ = 0.627, p < 0.001). These findings suggest that postural stability is not susceptible to placebo and nocebo influences. Still, there is a dissociation between objective and subjective performance, showing that expectations impact perceived but not actual performance, which could fuel motivation in rehabilitation settings.

From past pain to future pain through the pain of others: Information about other people's pain ratings can alleviate our subsequent pain

BACKGROUND

Previous studies have shown that pain memories have a profound impact on subsequent pain experiences. This study investigated whether pain ratings derived from other people can modify an individual's memory of past pain. This study also examined whether pain memory modified by others' pain ratings determines subsequent pain experiences.

METHODS

Participants were divided into two groups: an experimental group and a control group. Participants in both groups were exposed to pain stimulation; then, they recalled its intensity twice over a period of time; after a break, they were again exposed to pain stimulation of the same intensity. The final sample consisted of 53 participants. The only difference between the experimental group and the control group was that in the former the pain ratings of other alleged participants were presented between the two consecutive pain recalls. These ratings suggested that other people experienced the same pain as less intense.

RESULTS

The pain ratings derived from other people did not alter the pain memory; nevertheless, they affected an individual's next pain experience even for a certain period of time after their presentation. This type of pain-related information shaped participants' subsequent pain experiences regardless of their empathy, conformity, and susceptibility to social influence.

CONCLUSIONS

Information on pain derived from other people not only shapes the response to a novel stimulation but also substantially modifies the subsequent experience of that stimulation.

SIGNIFICANCE

The study demonstrates the importance of social information on pain and provides evidence that this type of information substantially modifies the subsequent experience of the same pain. These results suggest that social information on pain can be used to alleviate pain associated with recurring medical procedures and thus increase patients' willingness to continue treatment.

Targeting neural correlates of placebo effects

Harnessing the placebo effects would prompt critical ramifications for research and clinical practice. Noninvasive brain stimulation (NIBS) techniques, such as transcranial magnetic stimulation and multifocal transcranial electric stimulation, could manipulate the placebo response by modulating the activity and excitability of its neural correlates. To identify potential stimulation targets, we conducted a meta-analysis to investigate placebo-associated regions in healthy volunteers, including studies with emotional components and painful stimuli. Using biophysical modeling, we identified NIBS solutions to manipulate placebo effects by targeting either a single key region or multiple connected areas. Moving to a network-oriented approach, we then ran a quantitative network mapping analysis on the functional connectivity profile of clusters emerging from the meta-analysis. As a result, we suggest a multielectrode optimized montage engaging the connectivity patterns of placebo-associated functional brain networks. These NIBS solutions hope to provide a starting point to actively control, modulate or enhance placebo effects in future clinical studies and cognitive enhancement studies.

Implementation of active injury management (AIM) in youth with acute concussion: A randomized controlled trial

BACKGROUND

Nearly 2 million youth seek acute medical care following concussion in the U.S. each year. Current standard of care recommends rest for the first 48 h after a concussion. However, research suggests that prolonged rest may lengthen recovery time especially for patients with certain risk profiles. Research indicates that physical activity and behavioral management interventions (sleep, stress management) may enhance recovery. To date, there is limited empirical evidence to inform acute (<72 h) concussion recommendations for physical activity and behavioral management in adolescents.

OBJECTIVE

To determine the effectiveness of physical activity and behavioral management for acute concussion in adolescents and young adults, and to evaluate the role of patient characteristics on treatment response.

METHODS

This multicenter prospective randomized controlled trial will determine which combination of physical activity and behavioral management is most effective for patients 11-24 years old who present to the emergency department or concussion clinic within 72 h of injury. Participants are randomized into: 1) rest, 2) physical activity, 3) mobile health application (mHealth) behavioral management, or 4) physical activity and mHealth app conditions. Assessments at enrollment, 3-5 days, 14 days, 1 month, and 2 months include: concussion symptoms, balance, vestibular-ocular and cognitive assessments, quality of life, and recovery time. Somatic symptoms and other risk factors are evaluated at enrollment. Compliance with treatment and symptoms are assessed daily using actigraph and daily self-report. The primary study outcome is symptoms at 14 days.

CONCLUSION

Prescribed physical activity and behavioral management may improve outcomes in youth following acute concussion.

Instructions and experiential learning have similar impacts on pain and pain-related brain responses but produce dissociations in value-based reversal learning

Recent data suggest that interactions between systems involved in higher order knowledge and associative learning drive responses during value-based learning. However, it is unknown how these systems impact subjective responses, such as pain. We tested how instructions and reversal learning influence pain and pain-evoked brain activation. Healthy volunteers (n=40) were either instructed about contingencies between cues and aversive outcomes or learned through experience in a paradigm where contingencies reversed three times. We measured predictive cue effects on pain and heat-evoked brain responses using functional magnetic resonance imaging. Predictive cues dynamically modulated pain perception as contingencies changed, regardless of whether participants received contingency instructions. Heat-evoked responses in the insula, anterior cingulate, and other regions updated as contingencies changed, and responses in the prefrontal cortex mediated dynamic cue effects on pain, whereas responses in the brainstem’s rostroventral medulla (RVM) were shaped by initial contingencies throughout the task. Quantitative modeling revealed that expected value was shaped purely by instructions in the Instructed Group, whereas expected value updated dynamically in the Uninstructed Group as a function of error-based learning. These differences were accompanied by dissociations in the neural correlates of value-based learning in the rostral anterior cingulate, thalamus, and posterior insula, among other regions. These results show how predictions dynamically impact subjective pain. Moreover, imaging data delineate three types of networks involved in pain generation and value-based learning: those that respond to initial contingencies, those that update dynamically during feedback-driven learning as contingencies change, and those that are sensitive to instruction. Together, these findings provide multiple points of entry for therapies designs to impact pain.

Post-error adjustments depend causally on executive attention: Evidence from an intervention study

Detecting and correcting execution errors is crucial for safe and efficient goal-directed behavior. Despite intensive investigations on error processing, the cognitive foundations of this process remain unclear. Based on the presumed relation between executive attention (EA) and error processing, we implemented a seven-day EA intervention by adopting the Posner cueing paradigm to test the potential causal link from EA to error processing in healthy adults. The experimental group (high EA, HEA) was trained on the Posner cueing paradigm, with a ratio of invalid cue (IC) trials to valid cue (VC) trials of 5:1 and a corresponding ratio of 1:1 in the active control group (low EA, LEA). We found that the EA intervention improved EA across intervention sessions. Critically, after the EA intervention, the HEA group showed that post-error accuracy (PEA) was restored to the same level as the post-correct accuracy (in comparison with the LEA group). However, post-error slowing and the flanker effect were not modulated by the EA intervention. Furthermore, we observed that the changes in the accuracy of VC trials positively predicted the changes in PEA and that the two groups were classified according to the changes in PEA with a 61.3% accuracy. Based on these results, we propose that EA causally drives error processing. And the capabilities of the “actively catch” more attention resources and the automatic mismatch processing developed after EA intervention is transferable to error processing, thereby directly resulting in the gains in post-error adjustments. Our work informs the potential cognitive mechanisms underlying this causal link.

Effects of Generic Exchange of Levodopa Medication in Patients With Parkinson Disease

OBJECTIVES

Generic exchange is common practice in most healthcare systems. This study investigated how patients with Parkinson disease (PD) perceived a switch of their levodopa medication and the resulting effects on their PD symptoms.

METHODS

A questionnaire was developed, piloted, and finally distributed to 13,857 members of the national PD patient support group. It was designed to be completed by patients and their pharmacies. χ 2 tests for independence statistics with or without Monte Carlo simulation were performed. Cramér φ and Cramér V were calculated. McNemar test was used to investigate whether a generic switch of a levodopa-containing medication had an impact on PD symptoms.

RESULTS

Analyses were done with 410 finalized respondents of 13,857 distributed questionnaires. More than half of the responders were 75 years or older and rated themselves Hoehn and Yahr stages 3 to 5. Most patients were confused by a change of their medication. A total of 54.7% of the switchers (n = 148) reported swallowing difficulties with medication, which was significantly more frequent than with nonswitchers (37.3% of 204, P = 0.001). Adverse effects related to the switch were reported by 26.6% of all switchers (switchback rate, 20.5%). The patients at higher Hoehn and Yahr stages were affected to a greater extend.

CONCLUSIONS

Patients, who experienced any brand switch of their levodopa medication, frequently expressed distrust and confusion. Swallowing difficulties and negative effects on their symptoms were problems, which were more pronounced in advanced disease stages. It remains unclear whether the detrimental impact on therapy was caused by the brand switch or by a nocebo effect.

Effects of Self-Efficacy and Outcome Expectations on Motor Imagery-Induced Thermal and Mechanical Hypoalgesia: A Single-Blind Randomised Controlled Trial

The main aim of this study was to assess whether self-efficacy (SE) and outcome expectations (OEs) modulate the hypoalgesic effect induced by motor imagery (MI). A total of 75 asymptomatic participants were randomly assigned to the positive (SE+, OE+), negative (SE-, OE-) or non-expectation (CG) groups. Heat pain threshold (HPT) and pain pressure threshold (PPT) were the main variables. Cold detection threshold (CDT), warm detection threshold (WDT), heart rate (HR) and perceived fatigue were the secondary variables. The variables were assessed preintervention, immediately postintervention and 10 min postintervention, except for HR, which was measured continuously during the intervention. Regarding HPT, significant within-group pre-post differences were found in the OE+ group, with a low effect size (p = 0.01, d = -0.39). With regard to ΔPPT, significant intergroup differences were found in Δpost-pre between the SE+ and CG groups (p = 0.012, d = 1.04) and also between SE+ and OE- (p = 0.006, d = 1.08), both with a large effect size. CG, SE-, and OE- groups had poorer CDT and WDT. Regarding HR, significant intergroup differences were found in the postintervention measurement between OE+ and SE-, with a large effect size (p = 0.016, d = 1.34). Lastly, no between-group differences were found regarding perceived fatigue (p > 0.05). The results obtained showed that positive expectations have a slight influence on the increase in heat and mechanical pain detection thresholds. Positive and non-expectancy groups showed an autonomic activation. The results also showed that negative expectations led to poorer perceptual processes.

Central correlates of placebo effects in nausea differ between men and women

INTRODUCTION

Despite growing evidence validating placebo effects in nausea, little is known about the underlying cortical mechanisms in women and men. Therefore, the present study examined sex differences and electroencephalography (EEG) characteristics of the placebo effect on nausea.

METHODS

On 2 consecutive days, 90 healthy subjects (45 females) were exposed to a nauseating visual stimulus. Nausea was continuously rated on an 11-point numeric rating scale, and 32 EEG channels were recorded. On day 2, subjects were randomly allocated to either placebo treatment or no treatment: the placebo group received sham acupuncture, whereas the control group did not receive any intervention.

RESULTS

In contrast to the control group, both sexes in the placebo group showed reduced signs for anticipatory nausea in the EEG, indexed by increased frontal lobe and anterior cingulate activity. Among women, the improvement in perceived nausea in the placebo group was accompanied by decreased activation in the parietal, frontal, and temporal lobes. In contrast, the placebo-related improvement of perceived nausea in men was accompanied by increased activation in the limbic and sublobar (insular) lobes.

CONCLUSION

Activation of the parietal lobe in women during the placebo intervention may reflect altered afferent activity from gastric mechanoreceptors during nausea-induced tachyarrhythmia, whereas in men, altered interoceptive signals in the insular cortex might play a role. Thus, the results suggest different cerebral mechanisms underlying the placebo effects in men and women, which could have implications for the treatment of nausea.

Counterconditioning as Treatment to Reduce Nocebo Effects in Persistent Physical Symptoms: Treatment Protocol and Study Design

Persistent physical symptoms have a high prevalence and a large impact for patients and society. To date, treatment effects for these symptoms are often limited. Nocebo effects (i.e., negative outcomes that are not attributable to active treatment components) have a substantial influence on treatment success and can be established via learning through classical conditioning. Therefore, interventions aimed at reducing nocebo effects by means of counterconditioning, in which an alternative association (inhibiting the previous association) is learned, could be a promising method for improving physical symptoms. In experimental studies, counterconditioning has been shown promising in reducing experimentally-induced nocebo effects on pain and itch. Application of counterconditioning procedures to reduce nocebo effects on clinical symptoms has yet to be researched. This paper provides a protocol of a 6-week counterconditioning intervention aimed at reducing nocebo effects and clinical pain in patients with fibromyalgia. A study in patients with fibromyalgia is proposed to examine the feasibility and potential effectiveness of this counterconditioning intervention as a novel treatment method for reducing nocebo effects and generalization to clinical pain symptoms. Results can help design an optimized treatment protocol for reducing nocebo effects, based on the experiences of participants and the first indications of treatment efficacy.

Greater baseline pain inclusion criteria in clinical trials increase regression to the mean effect: a modelling study

ABSTRACT

We modelled the effects of pain intensity inclusion thresholds (3/10, 4/10, and 5/10 on a 0- to 10-point numerical pain rating scale) on the magnitude of the regression to the mean effect under conditions that were consistent with the sample mean and variance, and intermeasurement correlation observed in clinical trials for the management of chronic pain. All data were modelled on a hypothetical placebo control group. We found a progressive increase in the mean pain intensity as the pain inclusion threshold increased, but this increase was not uniform, having an increasing effect on baseline measurements compared with study endpoint measurements as the threshold was increased. That is, the regression to the mean effect was magnified by increasing inclusion thresholds. Furthermore, the effect increasing pain inclusion thresholds had on the regression to the mean effect was increased by decreasing sample mean values at baseline and intermeasurement correlations, and increasing sample variance. At its smallest, the regression to the mean effect was 0.13/10 (95% confidence interval: 0.03/10-0.24/10; threshold: 3/10, baseline mean pain: 6.5/10, SD: 1.6/10, and correlation: 0.44), and at its greatest, it was 0.78/10 (95% confidence interval: 0.63/10-0.94/10; threshold: 5/10, baseline mean pain: 6/10, SD: 1.8/10, and correlation: 0.19). We have shown that using pain inclusion thresholds in clinical trials drives progressively larger regression to the mean effects. We believe that a threshold of 3/10 offers the best compromise between maintaining assay sensitivity (the goal of thresholds) and the size of the regression to the mean effect.

Oxytocin and the social facilitation of placebo effects

Significant clinical improvement is often observed in patients who receive placebo treatment in randomized double-blind placebo-controlled trials. While a proportion of this "improvement" reflects experimental design limitations (e.g., reliance on subjective outcomes, unbalanced groups, reporting biases), some of it reflects genuine improvement corroborated by physiological change. Converging evidence across diverse medical conditions suggests that clinically-relevant benefits from placebo treatment are associated with the activation of brain reward circuits. In parallel, evidence has accumulated showing that such benefits are facilitated by clinicians that demonstrate warmth and proficiency during interactions with patients. Here, we integrate research on these neural and social aspects of placebo effects with evidence linking oxytocin and social reward to advance a neurobiological account for the social facilitation of placebo effects. This account frames oxytocin as a key mediator of treatment success across a wide-spectrum of interventions that increase social connectedness, thereby providing a biological basis for assessing this fundamental non-specific element of medical care.

Validating a biosignature-predicting placebo pill response in chronic pain in the settings of a randomized controlled trial

ABSTRACT

The objective of this study is to validate a placebo pill response predictive model-a biosignature-that classifies chronic pain patients into placebo responders (predicted-PTxResp) and nonresponders (predicted-PTxNonR) and test whether it can dissociate placebo and active treatment responses. The model, based on psychological and brain functional connectivity, was derived in our previous study and blindly applied to current trial participants. Ninety-four chronic low back pain (CLBP) patients were classified into predicted-PTxResp or predicted-PTxNonR and randomized into no treatment, placebo treatment, or naproxen treatment. To monitor analgesia, back pain intensity was collected twice a day: 3 weeks baseline, 6 weeks of treatment, and 3 weeks of washout. Eighty-nine CLBP patients were included in the intent-to-treat analyses and 77 CLBP patients in the per-protocol analyses. Both analyses showed similar results. At the group level, the predictive model performed remarkably well, dissociating the separate effect sizes of pure placebo response and pure active treatment response and demonstrating that these effects interacted additively. Pain relief was about 15% stronger in the predicted-PTxResp compared with the predicted-PTxNonR receiving either placebo or naproxen, and the predicted-PTxNonR successfully isolated the active drug effect. At a single subject level, the biosignature better predicted placebo nonresponders, with poor accuracy. One component of the biosignature (dorsolateral prefrontal cortex-precentral gyrus functional connectivity) could be generalized across 3 placebo studies and in 2 different cohorts-CLBP and osteoarthritis pain patients. This study shows that a biosignature can predict placebo response at a group level in the setting of a randomized controlled trial.

Verbal Suggestion Modulates the Sense of Ownership and Heat Pain Threshold During the "Injured" Rubber Hand Illusion

The appearance of the self-body influences the feeling that one's body belongs to oneself, that is, a sense of ownership (SoO) and pain perception. This can be identified by measuring the SoO and pain thresholds after performing the rubber hand illusion (RHI) with an injured rubber hand. The generation of SoO is thought to be caused by multisensory integration of bottom-up factors (vision, proprioceptive, and touch), and by top-down factors, such as the context effect. The appearance is one of the context effects which may become more effective when used simultaneously with other context effects (e.g., verbal suggestion). However, in the RHI, when appearance and other context effects are used simultaneously, the effect is unclear. In this study, we attempted to identify the influence of verbal suggestion on the SoO and heat pain threshold (HPT). As a preliminary step, in Experiment 1, the "normal" rubber hand and "penetrated nail" as injured rubber hand were used to clarify the context effect with appearance alone during RHI (synchronous/asynchronous), which was conducted within-subjects. In Experiment 2, we only used the "penetrated nail" rubber hand to clarify the context effect with verbal suggestion and appearance during RHI. We randomly classified participants into two suggestion groups ("fear" and "no-fear"). The RHI (synchronous/asynchronous) was conducted for each group. In each experiment, the effect of each condition was assessed by subjective measures of SoO, such as questionnaire, and objective measures of SoO, such as proprioceptive drift and electrodermal activity. Following RHI in each condition, HPT was measured. The main finding was that, in the synchronous condition, the "penetrated nail" appearance with "fear" verbal suggestion modulated questionnaire and HPT, but not electrodermal activity. We conclude that the context-included multisensory integration affected the subjective factors because it contains a higher cognitive process by verbal suggestion.

Psycho-Neuro-Endocrine-Immunological Basis of the Placebo Effect: Potential Applications beyond Pain Therapy

The placebo effect can be defined as the improvement of symptoms in a patient after the administration of an innocuous substance in a context that induces expectations regarding its effects. During recent years, it has been discovered that the placebo response not only has neurobiological functions on analgesia, but that it is also capable of generating effects on the immune and endocrine systems. The possible integration of changes in different systems of the organism could favor the well-being of the individuals and go hand in hand with conventional treatment for multiple diseases. In this sense, classic conditioning and setting expectations stand out as psychological mechanisms implicated in the placebo effect. Recent advances in neuroimaging studies suggest a relationship between the placebo response and the opioid, cannabinoid, and monoaminergic systems. Likewise, a possible immune response conditioned by the placebo effect has been reported. There is evidence of immune suppression conditioned through the insular cortex and the amygdala, with noradrenalin as the responsible neurotransmitter. Finally, a conditioned response in the secretion of different hormones has been determined in different studies; however, the molecular mechanisms involved are not entirely known. Beyond studies about its mechanism of action, the placebo effect has proved to be useful in the clinical setting with promising results in the management of neurological, psychiatric, and immunologic disorders. However, more research is needed to better characterize its potential use. This review integrates current knowledge about the psycho-neuro-endocrine-immune basis of the placebo effect and its possible clinical applications.

Experience with opioids does not modify the brain network involved in expectations of placebo analgesia

Placebo analgesia (PA) is defined as a psychobiological phenomenon triggered by the information surrounding an analgesic drug instead of its inherent pharmacological properties. PA is hypothesized to be formed through either verbal suggestions or conditioning. The present study aims at disentangling the neural correlates of expectations effects with or without conditioning through prior experience using the model of PA.

We addressed this question by recruiting two groups of individuals holding comparable verbally‐induced expectations regarding morphine analgesia but either (i) with or (ii) without prior experience with opioids. We then contrasted the two groups' neurocognitive response to acute heat‐pain induction following the injection of sham morphine using electroencephalography (EEG). Topographic ERP analyses of the N2 and P2 pain evoked potential components allowed to test the hypothesis that PA involves distinct neural networks when induced by expectations with or without prior experience.

First, we confirmed that the two groups showed corresponding expectations of morphine analgesia (Hedges' g_s < .4 positive control criteria, g_s = .37 observed difference), and that our intervention induced a medium‐sized PA (Hedges' g_av ≥ .5 positive control, g_av = .6 observed PA). We then tested our hypothesis on the recruitment of different PA‐associated brain networks in individuals with versus without prior experience with opioids and found no evidence for a topographic N2 and P2 ERP components difference between the two groups. Our results thus suggest that in the presence of verbally‐induced expectations, modifications in the PA‐associated brain activity by conditioning are either absent or very small.

Increasing the Effectiveness of a Physical Activity Smartphone Intervention With Positive Suggestions: Randomized Controlled Trial

Background

eHealth interventions have the potential to increase the physical activity of users. However, their effectiveness varies, and they often have only short-term effects. A possible way of enhancing their effectiveness is to increase the positive outcome expectations of users by giving them positive suggestions regarding the effectiveness of the intervention. It has been shown that when individuals have positive expectations regarding various types of interventions, they tend to benefit from these interventions more.

Objective

The main objective of this web-based study is to investigate whether positive suggestions can change the expectations of participants regarding the effectiveness of a smartphone physical activity intervention and subsequently enhance the number of steps the participants take during the intervention. In addition, we study whether suggestions affect perceived app effectiveness, engagement with the app, self-reported vitality, and fatigue of the participants.

Methods

This study involved a 21-day fully automated physical activity intervention aimed at helping participants to walk more steps. The intervention was delivered via a smartphone-based app that delivered specific tasks to participants (eg, setting activity goals or looking for social support) and recorded their daily step count. Participants were randomized to either a positive suggestions group (69/133, 51.9%) or a control group (64/133, 48.1%). Positive suggestions emphasizing the effectiveness of the intervention were implemented in a web-based flyer sent to the participants before the intervention. Suggestions were repeated on days 8 and 15 of the intervention via the app.

Results

Participants significantly increased their daily step count from baseline compared with 21 days of the intervention (t₁₀₇=−8.62; P<.001) regardless of the suggestions. Participants in the positive suggestions group had more positive expectations regarding the app (B=−1.61, SE 0.47; P<.001) and higher expected engagement with the app (B=3.80, SE 0.63; P<.001) than the participants in the control group. No effects of suggestions on the step count (B=−22.05, SE 334.90; P=.95), perceived effectiveness of the app (B=0.78, SE 0.69; P=.26), engagement with the app (B=0.78, SE 0.75; P=.29), and vitality (B=0.01, SE 0.11; P=.95) were found. Positive suggestions decreased the fatigue of the participants during the 3 weeks of the intervention (B=0.11, SE 0.02; P<.001).

Conclusions

Although the suggestions did not affect the number of daily steps, they increased the positive expectations of the participants and decreased their fatigue. These results indicate that adding positive suggestions to eHealth physical activity interventions might be a promising way of influencing subjective but not objective outcomes of interventions. Future research should focus on finding ways of strengthening the suggestions, as they have the potential to boost the effectiveness of eHealth interventions.

Trial Registration

Open Science Framework 10.17605/OSF.IO/CWJES; https://osf.io/cwjes

Beliefs About Medicines Predict Side-Effects of Placebo Modafinil

BACKGROUND

Patients receiving placebo in clinical trials often report side-effects (nocebo effects), but contributing factors are still poorly understood.

PURPOSE

Using a sham trial of the cognition-enhancing "smart pill" Modafinil we tested whether medication beliefs and other psychological factors predicted detection and attribution of symptoms as side-effects to placebo.

METHODS

Healthy students (n = 201) completed measures assessing beliefs about medication, perceived sensitivity to medicines, negative affectivity, somatization, and body awareness; 66 were then randomized to receive Deceptive Placebo (told Modafinil-given placebo, 67 to Open Placebo (told placebo-given placebo, and 68 to No Placebo. Memory and attention tasks assessed cognitive enhancement. Nocebo effects were assessed by symptom checklist.

RESULTS

More symptoms were reported in the Deceptive Placebo condition (M = 2.65; SD = 2.27) than Open Placebo (M = 1.92; SD = 2.24; Mann-Whitney U = 1,654, z = 2.30, p = .022) or No Placebo (M = 1.68; SD = 1.75, Mann-Whitney U = 1,640, z = 2.74, p = .006). Participants were more likely to attribute symptoms to Modafinil side-effects if they believed pharmaceuticals to be generally harmful (incidence rate ratio [IRR] = 1.70, p = .019), had higher perceived sensitivity to medicines (IRR = 1.68, p = .011), stronger concerns about Modafinil (IRR = 2.10, p < .001), and higher negative affectivity (IRR = 2.37, p < .001).

CONCLUSIONS

Beliefs about medication are potentially modifiable predictors of the nocebo effect. These findings provide insight into side-effect reports to placebo and, potentially, active treatment.

Expectancy Effects Threaten the Inferential Validity of Synchrony-Prosociality Research

Many studies argue that synchronized movement increases prosocial attitudes and behavior. We reviewed meta-analytic evidence that reported effects of synchrony may be driven by experimenter expectancy, leading to experimenter bias; and participant expectancy, otherwise known as placebo effects. We found that a majority of published studies do not adequately control for experimenter bias and that multiple independent replication attempts with added controls have failed to find the original effects. In a preregistered experiment, we measured participant expectancy directly, asking whether participants have a priori expectations about synchrony and prosociality that match the findings in published literature. Expectations about the effects of synchrony on prosocial attitudes directly mirrored previous experimental findings (including both positive and null effects)-despite the participants not actually engaging in synchrony. On the basis of this evidence, we propose an alternative account of the reported bottom-up effects of synchrony on prosociality: the effects of synchrony on prosociality may be explicable as the result of top-down expectations invoked by placebo and experimenter effects.

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.

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.

The Role of Expectation and Beliefs on the Effects of Non-Invasive Brain Stimulation

Non-invasive brain stimulation (NIBS) techniques are used in clinical and cognitive neuroscience to induce a mild magnetic or electric field in the brain to modulate behavior and cortical activation. Despite the great body of literature demonstrating promising results, unexpected or even paradoxical outcomes are sometimes observed. This might be due either to technical and methodological issues (e.g., stimulation parameters, stimulated brain area), or to participants’ expectations and beliefs before and during the stimulation sessions. In this narrative review, we present some studies showing that placebo and nocebo effects, associated with positive and negative expectations, respectively, could be present in NIBS trials, both in experimental and in clinical settings. The lack of systematic evaluation of subjective expectations and beliefs before and after stimulation could represent a caveat that overshadows the potential contribution of placebo and nocebo effects in the outcome of NIBS trials.

A social affective neuroscience lens on placebo analgesia

Pain is a fundamental experience that promotes survival. In humans, pain stands at the intersection of multiple health crises: chronic pain, the opioid epidemic, and health disparities. The study of placebo analgesia highlights how social, cognitive, and affective processes can directly shape pain, and identifies potential paths for mitigating these crises. This review examines recent progress in the study of placebo analgesia through affective science. It focuses on how placebo effects are shaped by expectations, affect, and the social context surrounding treatment, and discusses neurobiological mechanisms of placebo, highlighting unanswered questions and implications for health. Collaborations between clinicians and social and affective scientists can address outstanding questions and leverage placebo to reduce pain and improve human health.

μ Opioid Antagonist Naltrexone Partially Abolishes the Antidepressant Placebo Effect and Reduces Orbitofrontal Cortex Encoding of Reinforcement

BACKGROUND

Like placebo analgesia, the antidepressant placebo effect appears to involve cortical and subcortical endogenous opioid signaling, yet the mechanism through which opioid release affects mood remains unclear. The orbitofrontal cortex (OFC)-which integrates various attributes of a stimulus to predict associated outcomes-has been implicated in placebo effects and is rich in μ opioid receptors. We hypothesized that naltrexone blockade of μ opioid receptors would blunt OFC-dependent antidepressant placebo effects.

METHODS

Twenty psychotropic-free patients with major depressive disorder completed a randomized, double-blind, placebo-controlled crossover study of 1 oral dose of 50 mg of naltrexone or matching placebo immediately before completing 2 sessions of the antidepressant placebo functional magnetic resonance imaging task. This task manipulates placebo-associated expectancies and their reinforcement while assessing expected and actual mood improvement.

RESULTS

Behaviorally, manipulations of antidepressant placebo expectancies and their reinforcement had positive, interactive effects on participants' expectancy and mood ratings. The high-expectancy condition recruited the dorsolateral and ventrolateral prefrontal cortex, as well as dorsal attention stream regions. Interestingly, increased dorsolateral and ventrolateral prefrontal cortex brain responses appeared to attenuate the antidepressant placebo effect. The administration of 1 oral dose of naltrexone, compared with placebo, partially abolished the interaction of the expectancy and reinforcement manipulation on mood and blocked reinforcement-induced responses in the right central OFC.

CONCLUSIONS

Our results show preliminary evidence for the role of μ opioid central OFC modulation in antidepressant placebo effects by positively biasing the value of placebo based on reinforcement and enhancing subsequent hedonic experiences.

Brain Network to Placebo and Nocebo Responses in Acute Experimental Lower Back Pain: A Multivariate Granger Causality Analysis of fMRI Data

Background and Objective: Placebo and nocebo responses are widely observed. Herein, we investigated the nocebo hyperalgesia and placebo analgesia responses in brain network in acute lower back pain (ALBP) model using multivariate Granger causality analysis (GCA). This approach analyses functional magnetic resonance imaging (fMRI) data for lagged-temporal correlation between different brain areas. Method: After completing the ALBP model, 20 healthy subjects were given two interventions, once during a placebo intervention and once during a nocebo intervention, pseudo-randomly ordered. fMRI scans were performed synchronously during each intervention, and visual analog scale (VAS) scores were collected at the end of each intervention. The fMRI data were then analyzed using multivariate GCA. Results: Our results found statistically significant differences in VAS scores from baseline (pain status) for both placebo and nocebo interventions, as well as between placebo and nocebo interventions. In placebo network, we found a negative lagged-temporal correlation between multiple brain areas, including the dorsolateral prefrontal cortex (DLPFC), secondary somatosensory cortex area, anterior cingulate cortex (ACC), and insular cortex (IC); and a positive lagged-temporal correlation between multiple brain areas, including IC, thalamus, ACC, as well as the supplementary motor area (SMA). In the nocebo network, we also found a positive lagged-temporal correlation between multiple brain areas, including the primary somatosensory cortex area, caudate, DLPFC and SMA. Conclusion: The results of this study suggest that both pain-related network and reward system are involved in placebo and nocebo responses. The placebo response mainly works by activating the reward system and inhibiting pain-related network, while the nocebo response is the opposite. Placebo network also involves the activation of opioid-mediated analgesia system (OMAS) and emotion pathway, while nocebo network involves the deactivation of emotional control. At the same time, through the construction of the GC network, we verified our hypothesis that nocebo and placebo networks share part of the same brain regions, but the two networks also have their own unique structural features.

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.

Harnessing Placebo Effects in Primary Care: Using the Person-Based Approach to Develop an Online Intervention to Enhance Practitioners' Communication of Clinical Empathy and Realistic Optimism During Consultations

Background: Empathic communication and positive messages are important components of "placebo" effects and can improve patient outcomes, including pain. Communicating empathy and optimism to patients within consultations may also enhance the effects of verum, i.e., non-placebo, treatments. This is particularly relevant for osteoarthritis, which is common, costly and difficult to manage. Digital interventions can be effective tools for changing practitioner behavior. This paper describes the systematic planning, development and optimization of an online intervention-"Empathico"-to help primary healthcare practitioners enhance their communication of clinical empathy and realistic optimism during consultations. Methods: The Person-Based Approach to intervention development was used. This entailed integrating insights from placebo and behavior change theory and evidence, and conducting primary and secondary qualitative research. Systematic literature reviews identified barriers, facilitators, and promising methods for enhancing clinical empathy and realistic optimism. Qualitative studies explored practitioners' and patients' perspectives, initially on the communication of clinical empathy and realistic optimism and subsequently on different iterations of the Empathico intervention. Insights from the literature reviews, qualitative studies and public contributor input were integrated into a logic model, behavioral analysis and principles that guided intervention development and optimization. Results: The Empathico intervention comprises 7 sections: Introduction, Empathy, Optimism, Application of Empathico for Osteoarthritis, Reflection on my Consultations, Setting Goals and Further Resources. Iterative refinement of Empathico, using feedback from patients and practitioners, resulted in highly positive feedback and helped to (1) contextualize evidence-based recommendations from placebo studies within the complexities of primary healthcare consultations and (2) ensure the intervention addressed practitioners' and patients' concerns and priorities. Conclusions: We have developed an evidence-based, theoretically-grounded intervention that should enable practitioners to better harness placebo effects of communication in consultations. The extensive use of qualitative research throughout the development and optimization process ensured that Empathico is highly acceptable and meaningful to practitioners. This means that practitioners are more likely to engage with Empathico and make changes to enhance their communication of clinical empathy and realistic optimism in clinical practice. Empathico is now ready to be evaluated in a large-scale randomized trial to explore its impact on patient outcomes.

Lay perspectives of the open-label placebo rationale: a qualitative study of participants in an experimental trial

OBJECTIVES

To analyse participants' concepts about the open-label placebo (OLP) effect; to explore their views about the discussion points that are applied in conventional OLP trials and to examine their experiences of taking part in an OLP trial.

DESIGN

A qualitative study using thematic analysis of semistructured interviews that were nested within a randomised controlled trial investigating experimental OLP analgesia (registered at ClinicalTrials.gov: NCT02578420).

PARTICIPANTS

30 healthy adults who took part in the randomised controlled trial.

RESULTS

Participants mostly conceptualised placebo as something that is inert and requires deception in order to be effective. Interviewees used a broad definition of placebos, going beyond a conventional notion of sugar pills. In contrast to the conventional OLP rationale, participants seldom emphasised classical conditioning as a mechanism of placebo effects, stressing a variety of other well-established components through which placebos might be therapeutic, whereas the conventional OLP disclosures state that 'a positive attitude helps but is not necessary', participants in our study applied other attitudes, such as 'it's worth a try'. When asked about their experiences during the trial, the majority emphasised that the concept of OLP was completely novel to them. Participants were rather sceptical about the efficacy of the intervention.

CONCLUSION

Integrating lay perspectives into the scientific rationale of OLP treatments might enhance the plausibility and credibility of the rationale in ethical treatments.

TRIAL REGISTRATION NUMBER

NCT02578420.

Order does matter: the combined effects of classical conditioning and verbal suggestions on placebo hypoalgesia and nocebo hyperalgesia

ABSTRACT

In most experimental studies in which verbal suggestion and classical conditioning are implemented together to induce placebo effects, the former precedes the latter. In naturally occurring situations, however, the information concerning pain does not always precede but often follows the pain experience. Moreover, this information is not always congruent with experience. This study investigates whether the chronology of verbal suggestion and conditioning, as well as their congruence, affects placebo hypoalgesia and nocebo hyperalgesia. The effects induced in 15 groups were compared. The participants in 8 experimental groups were presented with verbal suggestions that were either congruent or incongruent with classical conditioning. The verbal suggestions were provided either before or after conditioning. In 2 other experimental groups, placebo conditioning or nocebo conditioning was implemented without any verbal suggestion; in 2 groups, verbal suggestion of hypoalgesia or hyperalgesia without conditioning was applied. The control groups without any suggestions or conditioning were also included. Placebo hypoalgesia induced by congruent procedures was significantly stronger when the suggestion of hypoalgesia preceded rather than followed conditioning. The order of the congruent procedures did not affect the magnitude of nocebo hyperalgesia. In the groups in which incongruent procedures were implemented, placebo hypoalgesia or nocebo hyperalgesia was in line with the direction of the last-used procedure, regardless of whether it was conditioning or verbal suggestion. The results show that not the type of the procedure (verbal suggestion or conditioning), but the direction of the last-used procedure shapes pain-related expectancies and determines placebo effects.

Placebo response and effect in randomized clinical trials: meta-research with focus on contextual effects

BACKGROUND

Contextual effects (i.e., placebo response) refer to all health changes resulting from administering an apparently inactive treatment. In a randomized clinical trial (RCT), the overall treatment effect (i.e., the post-treatment effect in the intervention group) can be regarded as the true effect of the intervention plus the impact of contextual effects. This meta-research was conducted to examine the average proportion of the overall treatment effect attributable to contextual effects in RCTs across clinical conditions and treatments and explore whether it varies with trial contextual factors.

METHODS

Data was extracted from trials included in the main meta-analysis from the latest update of the Cochrane review on "Placebo interventions for all clinical conditions" (searched from 1966 to March 2008). Only RCTs reported in English having an experimental intervention group, a placebo comparator group, and a no-treatment control group were eligible.

RESULTS

In total, 186 trials (16,655 patients) were included. On average, 54% (0.54, 95%CI 0.46 to 0.64) of the overall treatment effect was attributable to contextual effects. The contextual effects were higher for trials with blinded outcome assessor and concealed allocation. The contextual effects appeared to increase proportional to the placebo effect, lower mean age, and proportion of females.

CONCLUSION

Approximately half of the overall treatment effect in RCTs seems attributable to contextual effects rather than to the specific effect of treatments. As the study did not include all important contextual factors (e.g., patient-provider interaction), the true proportion of contextual effects could differ from the study's results. However, contextual effects should be considered when assessing treatment effects in clinical practice.

TRIAL REGISTRATION

PROSPERO CRD42019130257 . Registered on April 19, 2019.