Is the placebo powerless? Update of a systematic review with 52 new randomized trials comparing placebo with no treatment

Clinical improvements due to specific effects and placebo effects in conservative interventions and changes observed with no treatment in randomized controlled trials of patients with chronic nonspecific low back pain: a systematic review and meta-analysis

ABSTRACT

Little is known about the contribution of placebo effects and changes observed with no treatment in interventions for nonspecific low back pain (NSLBP). This systematic review assessed the proportions of the overall treatment effect that may be attributable to specific treatment effects, placebo effects, and changes observed with no treatment in randomized controlled trials (RCTs) in patients with NSLBP. Trials published before 2019 were identified from a published systematic review, and the search was updated in MEDLINE, Embase, and Cochrane Central for trials published between January 2019 and March 2023. Three-arm RCTs comparing the effects of experimental interventions vs placebo control vs no intervention reporting pain intensity, physical function, and/or health-related quality of life (HRQoL) were included. Sixteen RCTs with 1436 adults with chronic NSLBP testing conservative and mainly passive interventions were included. For pain intensity (16 studies), 33%, 18%, and 49% of the overall short-term treatment effect was attributable to specific treatment effects, placebo effects, and changes observed with no treatment, respectively. For physical function (11 studies) and HRQoL (6 studies), these proportions were 34%, 13%, and 53%, and 11%, 41%, and 48%, respectively. These results show that approximately half of the overall treatment effect of conservative and mainly passive interventions for patients with chronic NSLBP is attributable to changes observed with no treatment, rather than specific or placebo effects of treatments. However, the certainty of evidence was very low to low, suggesting that the true effects might be markedly different from the effect sizes underlying these estimates.

A Fictionalist Account of Open-Label Placebo

The placebo effect is now generally defined widely as an individual's response to the psychosocial context of a clinical treatment, as distinct from the treatment's characteristic physiological effects. Some researchers, however, argue that such a wide definition leads to confusion and misleading implications. In response, they propose a narrow definition restricted to the therapeutic effects of deliberate placebo treatments. Within the framework of modern medicine, such a scope currently leaves one viable placebo treatment paradigm: the non-deceptive and non-concealed administration of "placebo pills" or open-label placebo (OLP) treatment. In this paper, I consider how the placebo effect occurs in OLP. I argue that a traditional, belief-based account of OLP is paradoxical. Instead, I propose an account based on the non-doxastic attitude of pretence, understood within a fictionalist framework.

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.

Alcohol and morality: one alcoholic drink is enough to make people declare to harm others and behave impurely

We aimed to understand if alcohol intoxication affects the willingness to violate moral foundations (care, fairness, authority, loyalty, and purity). We conducted a laboratory study (N = 387) with three randomized groups: alcohol intoxication, placebo, and control, measuring the sacralization of moral foundations via the Moral Foundations Sacredness Scale. The study showed intoxicated participants sacralized moral foundations of care and purity more often than participants from control and placebo groups. It means participants declared more willing to physically harm other people and animals and behave impurely, e.g., doing deviant sexual behaviors or selling their souls. No differences related to fairness, authority, and loyalty were found. Our study helps to understand the decision processes underlying immoral behaviors, including crimes. We showed that even one drink makes people change their judgments about what is right and wrong (in the cases of harmful and impure behaviors), and because this kind of judgment precedes immoral behaviors, our results may help explain why some people under the influence of alcohol break the rules by doing things which they would never do when sober.

Placebo response of sham acupuncture in patients with primary dysmenorrhea: A meta-analysis

BACKGROUND

The placebo response of sham acupuncture in patients with primary dysmenorrhea is a substantial factor associated with analgesia. However, the magnitude of the placebo response is unclear.

OBJECTIVE

This meta-analysis assessed the effects of sham acupuncture in patients with primary dysmenorrhea and the factors contributing to these effects.

SEARCH STRATEGY

PubMed, Embase, Web of Science, and Cochrane CENTRAL databases were searched from inception up to August 20, 2022.

INCLUSION CRITERIA

Randomized controlled trials (RCTs) using sham acupuncture as a control for female patients of reproductive age with primary dysmenorrhea were included.

DATA EXTRACTION AND ANALYSIS

Pain intensity, retrospective symptom scale, and health-related quality of life were outcome measures used in these trials. Placebo response was defined as the change in the outcome of interest from baseline to endpoint. We used standardized mean difference (SMD) to estimate the effect size of the placebo response.

RESULTS

Thirteen RCTs were included. The pooled placebo response size for pain intensity was the largest (SMD = -0.99; 95% confidence interval [CI], -1.31 to -0.68), followed by the retrospective symptom scale (Total frequency rating score: SMD = -0.20; 95% CI, -0.80 to -0.39. Average severity score: SMD = -0.35; 95% CI, -0.90 to -0.20) and physical component of SF-36 (SMD = 0.27; 95% CI, -0.17 to 0.72). Studies using blunt-tip needles, single-center trials, studies with a low risk of bias, studies in which patients had a longer disease course, studies in which clinicians had < 5 years of experience, and trials conducted outside Asia were more likely to have a lower placebo response.

CONCLUSION

Strong placebo response and some relative factors were found in patients with primary dysmenorrhea. PROSPERO registration number: CRD42022304215. Please cite this article as: Sun CY, Xiong ZY, Sun CY, Ma PH, Liu XY, Sun CY, Xin ZY, Liu BY, Liu CZ, Yan SY. Placebo response of sham acupuncture in patients with primary dysmenorrhea: A meta-analysis. J Integr Med. 2023; 21(5): 455-463.

The role of the communicated treatment rationale on treatment outcome: study protocol for a randomized controlled trial

BACKGROUND

Placebo effects are a well-established phenomenon in the treatment of depression. However, the mechanism underlying these effects are not fully understood. Treatment expectations are considered one explanation for why placebos work. Treatment expectations are likely to be affected by clinician-patient interactions. This study aims to investigate the role of the communicated treatment rationale in modulating treatment expectations and its effects on the treatment outcomes of a pharmacological and a psychological active placebo intervention for depression. In this study, treatment expectations are modulated by presenting illness models that are either congruent or incongruent with the treatment intervention that follows.

METHODS

This 2 × 2 randomized controlled trial will involve patients with major depression. Participants will either receive a biological or a psychological illness model from a clinician. Following this, they are randomly assigned to receive either a pharmacological or a psychological active placebo intervention. The illness model and the treatment are either congruent or incongruent with each other, resulting in four groups. In addition, a natural course control group will be included.

DISCUSSION

This study will provide insights into the mechanism of expectation modulation in active placebo treatments for major depression. The results may provide insights for clinicians to improve their communication with patients by focusing on treatment expectations. By identifying the factors that contribute to placebo effects, this study has the potential to improve the effectiveness of existing depression treatments and reduce the burden of this highly prevalent mental health condition.

TRIAL REGISTRATION

This trial has been registered prospectively at ClinicalTrials.gov under the identifier: NCT04719663. Registered on January 22, 2021.

A strong alcoholic drink does not influence self-assessments of the big five personality traits

cAlohol affects how people think, feel, and behave, and how they perceive the physical and social world around them. But does alcohol also influence how people perceive themselves? Past work points to a number of possibilities, suggesting intoxication could lead to positive biases, to negative biases, or have no effects on self-assessments at all. Here we tested whether alcoholic intoxication affects self-assessments of personality within the Big Five personality framework. We hypothesized that intoxicated participants would see themselves more positively than non-intoxicated individuals would. We conducted a preregistered laboratory experiment on participants divided into three groups: alcohol intoxication (n = 106), placebo (n = 114), and control conditions (n = 109). Contrary to predictions, we found no differences in self-assessments of personality across conditions. Findings point to the possibility that self-assessments of personality may be too stable to be affected by the momentary changes in thoughts and feelings caused by alcoholic intoxication.

Influence of placebo effect in mental disorders research: A systematic review and meta-analysis

BACKGROUND

Randomized controlled trials (RCT) in mental disorders research commonly use active control groups including psychotherapeutic shams or inactive medication. This meta-analysis assessed whether placebo conditions (active controls) had an effect compared to no treatment or usual care (passive controls).

METHODS

PubMed, Scopus, PsycINFO, PsycARTICLES, Ovid, the Cochrane Central Register of Controlled Trials and Web of Science were searched from inception to April 2021 and reference lists of relevant articles. Three-arm RCTs, including active and passive control groups, were selected. Where individual standardized mean difference (SMD) was calculable, random effects meta-analyses were performed to estimate an overall effect size with 95% confidence intervals (CI) comparing active vs passive controls. Heterogeneity was assessed using I² statistic and meta-regression. Funnel asymmetry was evaluated using Egger's test (Prospero registration: CRD42021242940).

RESULTS

24 articles with 25 relevant RCTs were included in the review, of which 11 studies were of high risk of bias. There was an improvement in outcomes favouring the placebo conditions, compared to passive controls, overall (25 studies, SMD 0.24, 95% CI 0.06-0.42, I² = 43%) and in subgroups with anxiety (SMD 0.45, 95% CI 0.07-0.84, I² = 59%) or depression (SMD 0.22, 95% CI 0.04-0.39, I² = 0%). Meta-regression did not show a significant explanation for heterogeneity. Egger's test showed no asymmetry (p = .200).

CONCLUSIONS

A small placebo effect was observed in mental disorders research overall, and in patients with anxiety or depression. These findings should be interpreted with caution in the light of heterogeneity and risk of bias.

Effect of plyometric training and neuromuscular electrical stimulation assisted strength training on muscular, sprint, and functional performances in collegiate male football players

Background

The study's objective was to analyze the influence of an 8-week neuromuscular electrical stimulation (NMES) with a plyometric (PT) and strength training (ST) program on muscular, sprint, and functional performances in collegiate male football players.

Methods

Sixty collegiate male football players participated in this randomized controlled trial single-blind study. All the participants were randomly divided into two groups: (1) NMES group (Experimental, n = 30) who received NMES assisted ST and (2) sham NMES group (Control, n = 30) who received sham NMES assisted ST. In addition, participants from both groups received a PT program; both groups received intervention on three days a week for 8-weeks. The study's outcomes, such as muscular, sprint, and functional performances, were assessed using a strength test (STN) for quadriceps muscle, sprint test (ST), and single-leg triple hop test (SLTHT), respectively, at baseline pre-intervention and 8-week post-intervention. The interaction between group and time was identified using a mixed design (2 × 2) ANOVA.

Results

Significant difference found across the two time points for the scores of STN: F (1.58) = 5,479.70, p < 0.05; SLTHT: F (1.58) = 118.17, p < 0.05; and ST: F (1.58) = 201.63, p < 0.05. Similarly, the significant differences were found between groups averaged across time for the scores of STN: F (1.58) = 759.62, p < 0.05 and ST: F (1.58) = 10.08, p < 0.05. In addition, after 8-week of training, Cohen's d observed between two groups a large to medium treatment's effect size for the outcome STN (d = 10.84) and ST (d = 1.31). However, a small effect size was observed only for the SLTHT (d = 0.613).

Conclusions

Findings suggest that the effect of PT and ST with either NMES or sham NMES are equally capable of enhancing muscular, sprint, and functional performances in collegiate male football players. However, PT and ST with NMES have shown an advantage over PT and ST with sham NMES in improving muscular performance and sprint performance among the same participants.

Point‐of‐care tools to support optometric care provision to people with age‐related macular degeneration: A randomised, placebo‐controlled trial

Purpose

Age‐related macular degeneration (AMD) is a leading cause of vision impairment. This randomised placebo‐controlled trial investigated whether point‐of‐care tools can improve optometrists' AMD knowledge and/or care provision.

Methods

Australian optometrists (n = 31) completed a demographics survey and theoretical AMD case study multiple‐choice questions (MCQs) to assess their confidence in AMD care provision and AMD knowledge. Participants were then randomly assigned to one of three point‐of‐care tools (online ‘Classification of Age‐related macular degeneration and Risk Assessment Tool’ (CARAT), paper CARAT, or ‘placebo’) to use when providing care to their subsequent 5–10 AMD patients. Participants self‐audited the compliance of their AMD care to best practice for these patients, and a similar number of consecutive patients seen prior to enrolment. Post‐intervention, participants retook the AMD knowledge MCQs and confidence survey.

Results

A total of 29 participants completed the study. At the study endpoint, clinical confidence relative to baseline improved with the paper CARAT, relative to placebo, for knowledge of AMD risk factors, asking patients about these factors and referring for medical retinal sub‐specialist care. There were no between‐group differences for the change in AMD knowledge scores. Considering record documentation for patients with any AMD severity, there were no significant between‐group differences for documenting patient risk factors, AMD severity, clinical examination techniques or management. In a sub‐analysis, the change from baseline in compliance for documenting discussions about patient smoking behaviours for early AMD patients was higher with use of the online CARAT relative to placebo (p = 0.04). For patients with intermediate AMD, the change from baseline in documenting the risk of progression to late AMD was greater among practitioners who used the paper CARAT, relative to placebo (p = 0.04).

Conclusions

This study demonstrates that point‐of‐care clinical tools can improve practitioner confidence and aspects of the documentation of AMD clinical care by optometrists as assessed by self‐audit.

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.

Alcohol and Placebo: The Role of Expectations and Social Influence

The placebo effect is frequently present in our lives when an expectation, associated with any psychoactive material, leads to subjective and physiological changes. The present work studies the role of expectancies associated with ethanol/alcohol in changes to the subjective state. In experimental situations, we examine how these expectations—with or without social influences—affect participants when consuming alcoholic, pseudo-alcoholic, or non-alcoholic cocktails. Psychological and physical changes can, to a significant extent, arise from an expectation-driven placebo effect. We suggest that expectations of inebriation formed by socialization and experiences can explain most of the behavioural changes following alcohol consumption. These effects seem to be stronger if the alcohol consumption happens in a social context and weaker if it is individually. Regarding the information effect, we suppose that the expectations will positively affect the drunkenness, i.e. toward the placebo “direction”: those who believe they are consuming a non-alcoholic cocktail will be less inebriated than those who know their drink contains alcohol. In this study, we successfully demonstrate the expectation-induced classical placebo effect in the misinformed participants who were, in fact, consuming non-alcoholic drinks. The “social” alcohol consumption further enhances the true or believed effects of the alcohol, and thus the participants reported their subjective feelings in lines with their manipulated expectations. As regards the effect of the alcohol, therefore, many other factors contribute in addition to the alcohol itself, the most important of which seem to be group effect, suggestions and expectations.

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.

Attempting to Separate Placebo Effects from Exercise in Chronic Pain: A Systematic Review and Meta-analysis

BACKGROUND

Pain is the most disabling characteristic of musculoskeletal disorders, and while exercise is promoted as an important treatment modality for chronic musculoskeletal conditions, the relative contribution of the specific effects of exercise training, placebo effects and non-specific effects such as natural history are not clear. The aim of this systematic review and meta-analysis was to determine the relative contribution of these factors to better understand the true effect of exercise training for reducing pain in chronic primary musculoskeletal pain conditions.

DESIGN

Systematic review with meta-analysis DATA SOURCES: MEDLINE, CINAHL, SPORTDiscus, EMBASE and CENTRAL from inception to February 2021. Reference lists of prior systematic reviews.

ELIGIBILITY CRITERIA

Randomised controlled trials of interventions that used exercise training compared to placebo, true control or usual care in adults with chronic primary musculoskeletal pain. The review was registered prospectively with PROSPERO (CRD42019141096).

RESULTS

We identified 79 eligible trials for quantitative analysis. Pairwise meta-analysis showed very low-quality evidence (GRADE criteria) that exercise training was not more effective than placebo (g [95% CI]: 0.94 [- 0.17, 2.06], P = 0.098, I² = 92.46%, studies: n = 4). Exercise training was more effective than true, no intervention controls (g [95% CI]: 0.99 [0.66, 1.32], P < 0.001, I² = 92.43%, studies: n = 42), usual care controls (g [95% CI]: 0.64 [0.44, 0.83], P < 0.001, I² = 76.52%, studies: n = 33), and when all controls combined (g [95% CI]: 0.84 [0.64, 1.04], P < 0.001, I² = 90.02%, studies: n = 79).

CONCLUSIONS

There is very low-quality evidence that exercise training is not more effective than non-exercise placebo treatments in chronic pain. Exercise training and the associated clinical encounter are more effective than true control or standard medical care for reductions in pain for adults with chronic musculoskeletal pain, with very low quality of evidence based on GRADE criteria.

Placebo From an Enactive Perspective

Due to their complexity and variability, placebo effects remain controversial. We suggest this is also due to a set of problematic assumptions (dualism, reductionism, individualism, passivity). We critically assess current explanations and empirical evidence and propose an alternative theoretical framework-the enactive approach to life and mind-based on recent developments in embodied cognitive science. We review core enactive concepts such as autonomy, agency, and sense-making. Following these ideas, we propose a move from binary distinctions (e.g., conscious vs. non-conscious) to the more workable categories of reflective and pre-reflective activity. We introduce an ontology of individuation, following the work of Gilbert Simondon, that allow us to see placebo interventions not as originating causal chains, but as modulators and triggers in the regulation of tensions between ongoing embodied and interpersonal processes. We describe these interrelated processes involving looping effects through three intertwined dimensions of embodiment: organic, sensorimotor, and intersubjective. Finally, we defend the need to investigate therapeutic interactions in terms of participatory sense-making, going beyond the identification of individual social traits (e.g., empathy, trust) that contribute to placebo effects. We discuss resonances and differences between the enactive proposal, popular explanations such as expectations and conditioning, and other approaches based on meaning responses and phenomenological/ecological ideas.

IMPACT OF THE PLACEBO EFFECT ON SYMPTOMS, QUALITY OF LIFE AND FUNCTIONAL OUTCOMES IN ANGINA PECTORIS: A meta-analysis of randomized placebo-controlled trials

BACKGROUND

The placebo effect is a well described phenomenon in blinded studies evaluating anti-anginal therapeutics, although its impact on clinical research metrics remains unknown. We conducted a systematic review and meta-analysis to quantify the impact of placebo on endpoints of symptoms, life-quality and functional outcomes in randomized placebo-controlled trials (RCTs) of symptomatic stable coronary artery disease.

METHODS

We systematically reviewed MEDLINE, EMBASE, and the Cochrane database for double-blind RCTs of anti-angina therapeutics. Patients randomized to the placebo-arm were the study population. Main outcomes were the changes in exercise performance (exercise treadmill test [ETT] parameters), quality of life (Seattle Angina Questionnaire domains), symptoms (Canadian Cardiovascular Society angina class) and drug usage (nitroglycerin tabs/week) between baseline and following placebo. The primary outcome was ETT total duration time. Data were pooled with a random effect model.

RESULTS

Seventy-eight RCTs (83% drug-controlled, 17% procedure-controlled) were included encompassing 4,925 patients randomized to placebo. ETT total duration time was significantly improved following placebo as compared to baseline (mean [95% confidence interval]: 29.2 [20.6-37.8] seconds) with evidence of high heterogeneity (I 2 = 98%) At subgroup analysis, crossover design was associated with a smaller placebo effect on ETT performance than parallel study design (p for interaction=0.001). A significant placebo effect was observed for all secondary outcomes with overall high heterogeneity.

CONCLUSION

A substantial placebo effect was present in angina RCTs across a variety of functional and life-quality metrics. High variability in placebo effect size was present, mostly unexplained by differences in study and patient characteristics (PROSPERO CRD42019132797).

Effectiveness of placebo interventions for patients with nonspecific low back pain: a systematic review and meta-analysis

ABSTRACT

Little is known about the effectiveness of placebo interventions in patients with nonspecific low back pain (LBP). This systematic review assessed the magnitude of the effects of placebo interventions as compared to no intervention in randomized controlled trials (RCTs) including patients with LBP. Embase, MEDLINE (Ovid), and Cochrane CENTRAL databases were searched from inception to December 5, 2019. Randomized controlled trials comparing placebo intervention vs no intervention in adult patients with nonspecific LBP were included. Pain intensity, physical functioning, and health-related quality of life measured at short-term, medium-term, and long-term follow-up were the outcomes of this review. Twenty-one randomized controlled trials were included; one concerning acute LBP and one subacute LBP, whereas 19 studies reported on chronic LBP. In chronic LBP, placebo interventions were more effective than no intervention at short-term follow-up for pain intensity (standardized mean difference = -0.37, 95% confidence interval [CI] = -0.55 to -0.18, moderate-quality evidence), physical functioning (standardized mean difference -0.19, 95% CI = -0.39-0.01, moderate-quality evidence), and physical quality of life (mean difference = -2.71, 95% CI = -4.71-0.71, high-quality evidence), respectively. These effects were not significant at medium-term follow-up, and no data were available at long-term follow-up. These results show placebo interventions are more effective than no intervention at short-term follow-up in patients with chronic LBP. However, the magnitude of the effects is probably not clinically relevant (approximately 8 points on a 0-100 pain scale). Future research should identify effect modifiers and causal mechanisms explaining the short-term effects of placebo interventions in patients with chronic LBP.

Effects of open-label placebos in clinical trials: a systematic review and meta-analysis

Open-label placebos (OLPs) are placebos without deception in the sense that patients know that they are receiving a placebo. The objective of our study is to systematically review and analyze the effect of OLPs in comparison to no treatment in clinical trials. A systematic literature search was carried out in February 2020. Randomized controlled trials of any medical condition or mental disorder comparing OLPs to no treatment were included. Data extraction and risk of bias rating were independently assessed. 1246 records were screened and thirteen studies were included into the systematic review. Eleven trials were eligible for meta-analysis. These trials assessed effects of OLPs on back pain, cancer-related fatigue, attention deficit hyperactivity disorder, allergic rhinitis, major depression, irritable bowel syndrome and menopausal hot flushes. Risk of bias was moderate among all studies. We found a significant overall effect (standardized mean difference = 0.72, 95% Cl 0.39–1.05, p < 0.0001, I² = 76%) of OLP. Thus, OLPs appear to be a promising treatment in different conditions but the respective research is in its infancy. More research is needed, especially with respect to different medical and mental disorders and instructions accompanying the OLP administration as well as the role of expectations and mindsets.

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

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

Effect of Electroacupuncture versus Sham Electroacupuncture in Patients with Knee Osteoarthritis: A Pilot Randomized Controlled Trial

Objective

To explore the feasibility of evaluating the effectiveness and safety of electroacupuncture versus sham electroacupuncture for patients with knee osteoarthritis (KOA).

Method

A pilot randomized controlled trial was conducted at a teaching hospital in Beijing. A total of 30 patients with KOA (Kellgren grade II or III) were randomly allocated to an eight-week treatment of either electroacupuncture or sham electroacupuncture. Patients and outcome assessors were blinded to group allocation. The primary outcome was the proportion of responders achieving at least 1.14 seconds decrease in the Timed Up and Go Test (TUG) at week eight compared with baseline. The secondary outcomes included the knee range of motion, the knee extensor and flexor muscle strength, Lequesne index, 9-step stair-climb test (9-SCT), and TUG.

Results

Of 30 patients allocated to two groups, 27 (90%) completed the study. The proportion of responders was 53.3% (8 of 15) for electroacupuncture group and 26.7% (4 of 15) for sham electroacupuncture group by the intention-to-treat analysis (P = 0.264). There was no statistically significant difference in TUG between the two groups at eight weeks (P = 0.856). The compliance rate measured according to patients who conformed to the protocol and had received treatments ≥20 times was 93.3% (28 of 30). The dropout rate was 20% (3 of 15). Adverse effects were not reported in the study.

Conclusion

Our research demonstrated that further evaluation of the effectiveness of electroacupuncture versus sham electroacupuncture was feasible and safe for patients with KOA. Whether or not the electroacupuncture can improve the physical functions of knee joint, expand the knee range of motion, and increase the extensor and flexor muscle strength more significantly than sham electroacupuncture, future studies can be designed with larger sample size, randomization design and less biases. This trial is registered with NCT03366363.

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.

Better than nothing: A historical account of placebos and placebo effects from modern to contemporary medicine

Throughout the history of medicine, multiple conceptions of "placebo" and "placebo effect" have often co-existed across different domains, and today the meaning of these concepts is still disputed. Against this background, this chapter provides a succinct account of the key events in the history of the concepts of "placebo," "placebo control," and "placebo effect." The first section reconstructs the etymology of the term "placebo" and its first introduction in medicine. The next sections provide an account of how placebos have been employed in both medical practice and scientific research in modern medicine. Later sections trace the emergence of the concepts of "placebo control" and "placebo effect" in the first half of the 20th century, from the first empirical studies investigating the effects of placebos up to the publication of Beecher's landmark article "The Powerful Placebo." Finally, the last two sections review the varieties of randomized, placebo-controlled trials (RCTs) in the second half of the 20th century, and the subsequent wave of empirical studies that, starting from the 1970s, have investigated the psychological, pharmacological and neurobiological mechanisms of placebo effects.

Quantifying the Difference between Active and Passive Control Groups in Cognitive Interventions Using two Meta-Analytical Approaches

Despite promising reports of broad cognitive benefit in studies of cognitive training, it has been argued that the reliance of many studies on no-intervention control groups (passive controls) make these reports difficult to interpret because placebo effects cannot be ruled out. Although researchers have recently been trying to incorporate more active controls, in which participants engage in an alternate intervention, previous work has been contentious as to whether this actually yields meaningfully different results. To better understand the influence of passive and active control groups on cognitive interventions, we conducted two meta-analyses to estimate their relative effect sizes. While the first one broadly surveyed the literature by compiling data from 34 meta-analyses, the second one synthesized data from 42 empirical studies that simultaneously employed both types of controls. Both analyses showed no meaningful performance difference between passive and active controls, suggesting that current active control placebo paradigms might not be appropriately designed to reliably capture these non-specific effects or that these effects are minimal in this literature.

Evaluating the Placebo Status of Nebulized Normal Saline in Patients With Acute Viral Bronchiolitis: A Systematic Review and Meta-analysis

IMPORTANCE

In therapeutic trials for acute viral bronchiolitis, consistent clinical improvement in groups that received nebulized normal saline (NS) as placebo raises the question of whether nebulized NS acts as a treatment rather than a placebo.

OBJECTIVE

To measure the short-term association of nebulized NS with physiologic measures of respiratory status in children with bronchiolitis by analyzing the changes in these measures between the use of nebulized NS and the use of other placebos and the changes before and after nebulized NS treatment.

DATA SOURCES

MEDLINE and Scopus were searched through March 2019, as were bibliographies of included studies and relevant systematic reviews, for randomized clinical trials evaluating nebulized therapies in bronchiolitis.

STUDY SELECTION

Randomized clinical trials comparing children 2 years or younger with bronchiolitis who were treated with nebulized NS were included. Studies enrolling a treatment group receiving an alternative placebo were included for comparison of NS with other placebos.

DATA EXTRACTION AND SYNTHESIS

Data abstraction was performed per PRISMA guidelines. Fixed- and random-effects, variance-weighted meta-analytic models were used.

MAIN OUTCOMES AND MEASURES

Pooled estimates of the association with respiratory scores, respiratory rates, and oxygen saturation within 60 minutes of treatment were generated for nebulized NS vs another placebo and for change before and after receiving nebulized NS.

RESULTS

A total of 29 studies including 1583 patients were included. Standardized mean differences in respiratory scores for nebulized NS vs other placebo (3 studies) favored nebulized NS by -0.9 points (95% CI, -1.2 to -0.6 points) at 60 minutes after treatment (P < .001). There were no differences in respiratory rate or oxygen saturation comparing nebulized NS with other placebo. The standardized mean difference in respiratory score (25 studies) after nebulized NS was -0.7 (95% CI, -0.7 to -0.6; I2 = 62%). The weighted mean difference in respiratory scores using a consistent scale (13 studies) after nebulized NS was -1.6 points (95% CI, -1.9 to -1.3 points; I2 = 72%). The weighted mean difference in respiratory rate (17 studies) after nebulized NS was -5.5 breaths per minute (95% CI, -6.3 to -4.6 breaths per minute; I2 = 24%). The weighted mean difference in oxygen saturation (23 studies) after nebulized NS was -0.4% (95% CI, -0.6% to -0.2%; I2 = 79%).

CONCLUSIONS AND RELEVANCE

Nebulized NS may be an active treatment for acute viral bronchiolitis. Further evaluation should occur to establish whether it is a true placebo.

Handling underlying discrete variables with bivariate mixed hidden Markov models in NONMEM

Non-linear mixed effects models typically deal with stochasticity in observed processes but models accounting for only observed processes may not be the most appropriate for all data. Hidden Markov models (HMMs) characterize the relationship between observed and hidden variables where the hidden variables can represent an underlying and unmeasurable disease status for example. Adding stochasticity to HMMs results in mixed HMMs (MHMMs) which potentially allow for the characterization of variability in unobservable processes. Further, HMMs can be extended to include more than one observation source and are then multivariate HMMs. In this work MHMMs were developed and applied in a chronic obstructive pulmonary disease example. The two hidden states included in the model were remission and exacerbation and two observation sources were considered, patient reported outcomes (PROs) and forced expiratory volume (FEV1). Estimation properties in the software NONMEM of model parameters were investigated with and without random and covariate effect parameters. The influence of including random and covariate effects of varying magnitudes on the parameters in the model was quantified and a power analysis was performed to compare the power of a single bivariate MHMM with two separate univariate MHMMs. A bivariate MHMM was developed for simulating and analysing hypothetical COPD data consisting of PRO and FEV1 measurements collected every week for 60 weeks. Parameter precision was high for all parameters with the exception of the variance of the transition rate dictating the transition from remission to exacerbation (relative root mean squared error [RRMSE] > 150%). Parameter precision was better with higher magnitudes of the transition probability parameters. A drug effect was included on the transition rate probability and the precision of the drug effect parameter improved with increasing magnitude of the parameter. The power to detect the drug effect was improved by utilizing a bivariate MHMM model over the univariate MHMM models where the number of subject required for 80% power was 25 with the bivariate MHMM model versus 63 in the univariate MHMM FEV1 model and > 100 in the univariate MHMM PRO model. The results advocates for the use of bivariate MHMM models when implementation is possible.

Acupuncture for the Treatment of Pain - A Mega-Placebo?

Several control conditions, such as penetrating sham acupuncture and non-penetrating placebo needles, have been used in clinical trials on acupuncture effects in chronic pain syndromes. All these control conditions are surprisingly effective with regard to their analgesic properties. These findings have fostered a discussion as to whether acupuncture is merely a placebo. Meta-analyses on the clinical effectiveness of placebo revealed that placebo interventions in general have minor, clinically important effects. Only in trials on pain and nausea, including acupuncture studies, did placebo effects vary from negligible to clinically important. At the same time, individual patient meta-analyses confirm that acupuncture is effective for the treatment of chronic pain, including small but statistically significant differences between acupuncture and sham acupuncture. All acupuncture control conditions induce de qi, a distinct stimulation associated with pain and needling which has been shown to be a nociceptive/pain stimulus. Acupuncture therefore probably activates the pain matrix in the brain in a bottom-up fashion via the spino-thalamic tract. Central nervous system effects of acupuncture can be modulated through expectations, which are believed to be a central component of the placebo response. However, further investigation is required to determine how strong the influence of placebo on the attenuation of activity in the pain matrix really is. A meta-analysis of individual participant functional magnetic imaging data reveals only weak effects of placebo on the activity of the pain network. The clinical acupuncture setting is comprised of a combination of a distinct neurophysiological stimulus, the needling stimulus/experience, and a complex treatment situation. A broader definition of placebo, such as that proposed by Howick (2017) acknowledges a role for expectation, treatment context, emotions, learning, and other contextual variables of a treatment situation. The inclusion of particular treatment feature as a definitional element permits a contextual definition of placebo, which in turn can be helpful in constructing future clinical trials on acupuncture.

The effects of acupuncture on pregnancy outcomes of in vitro fertilization: a systematic review and meta-analysis

BACKGROUND

The effects of acupuncture on in vitro fertilization (IVF) outcomes remain controversial. And the variation in participant, interventions, outcomes studied, and trial design may relate to the efficacy of adjuvant acupuncture.

METHODS

We searched digital databases for relevant studies, including Embase, PubMed, Cochrane Library and some Chinese databases up to December 2018, for randomized controlled trials (RCTs) evaluating the effects of acupuncture on women undergoing IVF. We included studies with intervention groups using needling, and control groups consisting of no acupuncture or sham (placebo) acupuncture. Primary outcomes were clinical pregnancy rate (CPR) and live birth rate (LBR). Meta-regression and subgroup analysis were conducted on the basis of eight pre-specified covariates to investigate the variances of the effects of adjuvant acupuncture on pregnancy rates and the sources of heterogeneity.

RESULTS

Twenty-seven studies with 6116 participants were included. The pooled clinical pregnancy rate (CPR) from all of acupuncture groups was significantly greater than that of control groups (RR 1.21, 95% CI: 1.07-1.38), whereas the pooled live birth rate (LBR) was not. Meta-regression subgroup analysis showed a more significant benefit of acupuncture for repeated IVF cycle proportion (number of women with a history of prior unsuccessful IVF attempt divided by number of women included in each trial) ≥ 50% group (CPR: RR 1.60, 95% CI: 1.28-2.00; LBR: RR 1.42, 95% CI: 1.05-1.92), and this covariate explained most of the heterogeneity (CPR and LBR: adjusted R2 = 100 and 87.90%). Similar results were found between CPR and number of acupuncture treatments (CPR: p = 0.002, adjusted R2 = 51.90%), but not LBR.

CONCLUSIONS

Our analysis finds a benefit of acupuncture for IVF outcomes in women with a history of unsuccessful IVF attempt, and number of acupuncture treatments is a potential influential factor. Given the poor reporting and methodological flaws of existing studies, studies with larger scales and better methodologies are needed to verify these findings.

Nocebo Effects and Negative Suggestions in Daily Clinical Practice - Forms, Impact and Approaches to Avoid Them

Medical situations are hot spots in the life of a patient with potentially long lasting effects arising from the use of either negative expressions or encouraging statements, or the lack of empathy or a positive physician-patient relationship. Health care personnel should be aware of and evaluate what patients are exposed to, hear and see. Knowing more about the effects of nocebos and negative suggestions, combined with increased attention to these matters, provides the basis for better recognition of detrimental influences in their own clinical environment and to be able to avoid, stop or neutralize them. After anamnesis patients should not be left with a focus on a negative past, but shifted to positive experiences prior to their illness, or to positive expectations in the future following surgery and rehabilitation. For example, after examining an injured leg the doctor should not turn to the computer for documentation unless he has shifted the patient's focus on the other, unimpaired leg. "Is that painful too? No? Good! Can you feel that? Yes? Perfect! Can you bend that knee, move these toes? Great! That's good." This example draws attention to the fact that negative effects (discussed in the following) substantially are dependent on the focus of the patient and thus can be affected by focus shift and distraction. Patients, their symptoms and their healing are negatively affected by the omission of placebo effects, by nocebo effects and by negative suggestions.

Role of placebo effects in pain and neuropsychiatric disorders

The placebo (and the nocebo) effect is a powerful determinant of health outcomes in clinical disease treatment and management. Efforts to completely eradicate placebo effects have shifted dynamically, as increasingly more researchers are tuned to the potentially beneficial effects of incorporating those uncontrollable placebo effects into clinical therapeutic strategies. In this review, we highlight the major findings from placebo research, elucidating the main neurobiological systems and candidate determinants of the placebo phenomenon, and illustrate a perspective that can effectively frame future research on the topic. Finally, we issue a call for increased research on the efficacy of therapeutic strategies that incorporate placebo "tools," and argue that clinical trials of the placebo response in neuropsychiatric diseases and disorders has important and far-reaching translational and clinical relevance.

Placebo Effects in Traumatic Brain Injury

In recent years, several randomized controlled trials evaluating pharmaceutical treatments for traumatic brain injury (TBI) have failed to demonstrate efficacy over placebo, with both active and placebo arms improving at comparable rates. These findings could be viewed in opposing ways, suggesting on the one hand failure of the tested outcome, but on the other, representing evidence of robust placebo effects in TBI. In this article, we examine several of the primary psychological processes driving placebo effects (verbal suggestion, cognitive re-framing, interpersonal interactions, conditioning, therapeutic alliance, anxiety reduction) as well as placebo neurobiology (top-down cortical regulation, reward system activation, dopaminergic and serotonergic neurotransmission). We then extrapolate from the literature to explore whether something inherent in TBI makes it particularly responsive to placebos. Viewed as such here, placebos may indeed represent a powerful and effective treatment for a variety of post-TBI complaints.

What Is the Role of the Placebo Effect for Pain Relief in Neurorehabilitation? Clinical Implications From the Italian Consensus Conference on Pain in Neurorehabilitation

Background

It is increasingly acknowledged that the outcomes of medical treatments are influenced by the context of the clinical encounter through the mechanisms of the placebo effect. The phenomenon of placebo analgesia might be exploited to maximize the efficacy of neurorehabilitation treatments. Since its intensity varies across neurological disorders, the Italian Consensus Conference on Pain in Neurorehabilitation (ICCP) summarized the studies on this field to provide guidance on its use.

Methods

A review of the existing reviews and meta-analyses was performed to assess the magnitude of the placebo effect in disorders that may undergo neurorehabilitation treatment. The search was performed on Pubmed using placebo, pain, and the names of neurological disorders as keywords. Methodological quality was assessed using a pre-existing checklist. Data about the magnitude of the placebo effect were extracted from the included reviews and were commented in a narrative form.

Results

11 articles were included in this review. Placebo treatments showed weak effects in central neuropathic pain (pain reduction from 0.44 to 0.66 on a 0-10 scale) and moderate effects in postherpetic neuralgia (1.16), in diabetic peripheral neuropathy (1.45), and in pain associated to HIV (1.82). Moderate effects were also found on pain due to fibromyalgia and migraine; only weak short-term effects were found in complex regional pain syndrome. Confounding variables might have influenced these results.

Clinical implications

These estimates should be interpreted with caution, but underscore that the placebo effect can be exploited in neurorehabilitation programs. It is not necessary to conceal its use from the patient. Knowledge of placebo mechanisms can be used to shape the doctor-patient relationship, to reduce the use of analgesic drugs and to train the patient to become an active agent of the therapy.

Placebo response and its determinants in children with ADHD across multiple observers and settings: A randomized clinical trial

This study aims to quantify placebo response (PR) in children with attention deficit hyperactivity disorder (ADHD) as assessed by parents and teachers and to explore some of its determinants. Five hundred and forty children with ADHD (ages 6-12) were recruited to a randomized, double-blind, placebo-controlled crossover trial with methylphenidate. The main outcome variable was Conners' Global Index (CGI), based on assessment of behaviour by parents (CGI-P) and teacher (CGI-T). PR was calculated as the difference between CGI-P/T scores at baseline and placebo week. There was a highly significant PR as assessed by the parents' and teachers' (p < 0.001). The magnitude of PR as assessed by parents was greater (10.57 points) compared to that assessed by teachers (3.93 points). The determinants of PR were different between parents and teachers. For parents, income, marital status, education, maternal smoking during pregnancy, and prior psychostimulant exposure (PPE) showed a significant effect on PR. For teachers, only ethnicity and PPE had an effect. The pattern of PR revealed two distinct profiles that may shed some light on the mechanisms involved in PR. PR in children with ADHD varies depending on the setting of the observations and the evaluator. Several psychosocial factors have been identified as modulators of PR. This is relevant for the design and interpretation of clinical trials and for clinical practice.

Blinding in trials of interventional procedures is possible and worthwhile

In this paper, we use evidence from our earlier review of surgical randomised controlled trials with a placebo arm to show that blinding in trials of interventional procedures is feasible. We give examples of ingenious strategies that have been used to simulate the active procedure and to make the placebo control indistinguishable from the active treatment. We discuss why it is important to blind of patients, assessors, and caregivers and what types of bias that may occur in interventional trials. Finally, we describe the benefits of blinding, from the obvious ones such as avoiding bias, as well as less evident benefits such as avoiding patient drop out in the control arm.

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.

Blinding in trials of interventional procedures is possible and worthwhile

In this paper, we use evidence from our earlier review of surgical randomised controlled trials with a placebo arm to show that blinding in trials of interventional procedures is feasible. We give examples of ingenious strategies that have been used to simulate the active procedure and to make the placebo control indistinguishable from the active treatment. We discuss why it is important to blind of patients, assessors, and caregivers and what types of bias that may occur in interventional trials. Finally, we describe the benefits of blinding, from the obvious ones such as avoiding bias, as well as less evident benefits such as avoiding patient drop out in the control arm.

The Placebo Analgesic Effect in Healthy Individuals and Patients: A Meta-Analysis

OBJECTIVE

The present meta-analysis investigates whether the magnitude of placebo analgesia is different in patients compared with healthy individuals and whether placebo analgesia is different in experimentally induced pain compared with clinical pain in patients.

METHODS

A literature search in Web of Science (ISI) on the terms "placebo analgesia" and "placebo analgesic" was conducted. The search resulted in 71 studies, including 4239 participants. Fifty-five studies included healthy individuals and 16 studies included patients. Of the 16 studies with patients, five studies investigated clinical pain and 11 studies investigated experimentally induced pain.

RESULTS

The average effect size was 1.24 for healthy individuals and 1.49 for patients. In the studies with patients, the average effect sizes of placebo treatment were 1.73 for experimentally induced pain and 1.05 for clinical pain. A χ test revealed that there were relatively more studies with patients compared with healthy volunteers in which there was a clinically significant reduction in pain (p = .040).

CONCLUSIONS

The findings suggest that patients benefited from placebo treatment to a greater degree than healthy individuals did and that studies on healthy individuals may underestimate the magnitude of the placebo analgesic effect in patients. Patients' clinical pain and experimentally induced pain respond to placebo to the same degree.

Effects of placebos without deception compared with no treatment: A systematic review and meta-analysis

OBJECTIVE

To investigate the clinical efficacy of open-label placebos compared with no treatment in a systematic review and meta-analysis.

METHODS

We searched the Cochrane Injuries Group's Specialised Register, The Cochrane Central Register of Controlled Trials (CENTRAL), Ovid MEDLINE(R) In-Process & Other Non-Indexed Citations (OvidSP), EMBASE (OvidSP), and clinical trials registers and screened reference lists. The search was run on 27^th April 2015. We included all randomized controlled trials of any medical condition with open-label placebo and no-treatment groups. Authors independently assessed records and extracted data. We excluded nonrandomized trials and nonclinical studies. Risk of bias was assessed using Cochrane criteria. We used random-effects model for meta-analysis.

RESULTS

We screened 348 publications, assessed 24 articles for eligibility and identified five trials (260 participants) that met inclusion criteria. The clinical conditions were: irritable bowel syndrome, depression, allergic rhinitis, back pain, and attention deficit hyperactivity disorder. The risk of bias was moderate. We found a positive effect for nondeceptive placebos (standardized mean difference 0.88, 95% CI 0.62 to 1.14, P < 0.00001, I² = 1%).

CONCLUSIONS

Open-label placebos appear to have positive clinical effects compared to no treatment. Caution is warranted when interpreting these results due to the limited number of trials identified, lack of blinding, and the fact that positive messages were included alongside open-label placebos. Larger definitive trials are now warranted to explore the potential patient benefit of open-label placebos, to investigate the relative contributions of positive suggestions, and ethical implications.

Harnessing the placebo effect: Exploring the influence of physician characteristics on placebo response

OBJECTIVE

Research on placebo/nocebo effects suggests that expectations can influence treatment outcomes, but placebo/nocebo effects are not always evident. This research demonstrates that a provider's social behavior moderates the effect of expectations on physiological outcomes.

METHODS

After inducing an allergic reaction in participants through a histamine skin prick test, a health care provider administered a cream with no active ingredients and set either positive expectations (cream will reduce reaction) or negative expectations (cream will increase reaction). The provider demonstrated either high or low warmth, or either high or low competence.

RESULTS

The impact of expectations on allergic response was enhanced when the provider acted both warmer and more competent and negated when the provider acted colder and less competent.

CONCLUSION

This study suggests that placebo effects should be construed not as a nuisance variable with mysterious impact but instead as a psychological phenomenon that can be understood and harnessed to improve treatment outcomes. (PsycINFO Database Record

Placebo Intervention Enhances Reward Learning in Healthy Individuals

According to the placebo-reward hypothesis, placebo is a reward-anticipation process that increases midbrain dopamine (DA) levels. Reward-based learning processes, such as reinforcement learning, involves a large part of the DA-ergic network that is also activated by the placebo intervention. Given the neurochemical overlap between placebo and reward learning, we investigated whether verbal instructions in conjunction with a placebo intervention are capable of enhancing reward learning in healthy individuals by using a monetary reward-based reinforcement-learning task. Placebo intervention was performed with non-invasive brain stimulation techniques. In a randomized, triple-blind, cross-over study we investigated this cognitive placebo effect in healthy individuals by manipulating the participants’ perceived uncertainty about the intervention’s efficacy. Volunteers in the purportedly low- and high-uncertainty conditions earned more money, responded more quickly and had a higher learning rate from monetary rewards relative to baseline. Participants in the purportedly high-uncertainty conditions showed enhanced reward learning, and a model-free computational analysis revealed a higher learning rate from monetary rewards compared to the purportedly low-uncertainty and baseline conditions. Our results indicate that the placebo response is able to enhance reward learning in healthy individuals, opening up exciting avenues for future research in placebo effects on other cognitive functions.

Different Disclosed Probabilities to Receive an Antiemetic Equally Decrease Subjective Symptoms in an Experimental Placebo Study: To Be or Not to Be Sure

PURPOSE

The purpose of this study was to examine whether the disclosed probability of receiving an antiemetic affects nausea.

METHODS

Forty-eight healthy participants (mean [SD] age, 26.8 [5.4] years; 50% female) were exposed to 5 × 2 minutes of nauseogenic body rotations on 2 days. On day 2, participants were randomized to 3 experimental groups that were given different instructions concerning the probability of receiving an antiemetic remedy (100%, 50%, or 0% probability), whereas all received an inert substance. Subjective symptoms, behavioral (rotation tolerance) measures, and physiologic (electrogastrogram) measures of nausea were assessed and mediator and moderator analyses performed for effects of expectations and psychological characteristics on outcomes.

FINDINGS

Disclosed probabilities of both 100% and 50% significantly reduced subjective symptoms of nausea in an equal manner compared with the 0% probability group from day 1 to day 2. This effect was found for neither rotation tolerance nor myoelectric gastric activity. Expectations and psychological characteristics did not affect the results found. Post hoc analyses revealed that women only seem to be susceptible to this placebo effect.

IMPLICATIONS

Nausea is susceptible to placebo effects independent of the disclosed probability of receiving a drug and of explicit expectations. In line with placebo research, this effect is probably attributable to central mechanisms, and it is speculated that it could be related to the reward circuitry and social interactions.

The magnitude and temporal changes of response in the placebo arm of surgical randomized controlled trials: a systematic review and meta-analysis

BACKGROUND

Understanding changes in the placebo arm is essential for correct design and interpretation of randomized controlled trials (RCTs). It is assumed that placebo response, defined as the total improvement in the placebo arm of surgical trials, is large; however, its precise magnitude and properties remain to be characterized. To the best of our knowledge, the temporal changes in the placebo arm have not been investigated. The aim of this paper was to determine, in surgical RCTs, the magnitude of placebo response and how it is affected by duration of follow-up.

METHODS

The databases of MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials and ClinicalTrials.gov were searched from their inception to 20 October 2015 for studies comparing the efficacy of a surgical intervention with placebo. Inclusion was not limited to any particular condition, intervention, outcome or patient population. The magnitude of placebo response was estimated using standardized mean differences (SMDs). Study estimates were pooled using random effects meta-analysis. Potential sources of heterogeneity were evaluated using stratification and meta-regression.

RESULTS

Database searches returned 88 studies, but for 41 studies SMDs could not be calculated, leaving 47 trials (involving 1744 participants) eligible for inclusion. There were no temporal changes in placebo response within the analysed trials. Meta-regression analysis showed that duration of follow-up did not have a significant effect on the magnitude of the placebo response and that the strongest predictor of placebo response was subjectivity of the outcome. The pooled effect in the placebo arm of studies with subjective outcomes was large (0.64, 95% CI 0.5 to 0.8) and remained significantly different from zero regardless of the duration of follow-up, whereas for objective outcomes, the effect was small (0.11, 95% CI 0.04 to 0.26) or non-significant across all time points.

CONCLUSIONS

This is the first study to investigate the temporal changes of placebo response in surgical trials and the first to investigate the sources of heterogeneity of placebo response. Placebo response in surgical trials was large for subjective outcomes, persisting as a time-invariant effect throughout blinded follow-up. Therefore, placebo response cannot be minimized in these types of outcomes through their appraisal at alternative time points. The analyses suggest that objective outcomes may be preferable as trial end-points. Where subjective outcomes are of primary interest, a placebo arm is necessary to control for placebo response.

Information without Implementation: A Practical Example for Developing a Best Practice Education Control Group

This article considers methodology for developing an education-only control group and proposes a simple approach to designing rigorous and well-accepted control groups. This approach is demonstrated in a large randomized trial. The Lifestyles trial (n = 367) compared three group interventions: (a) cognitive-behavioral treatment (CBT) for osteoarthritis pain, (b) CBT for osteoarthritis pain and insomnia, and (c) education-only control (EOC). EOC emulated the interventions excluding hypothesized treatment components and controlling for nonspecific treatment effects. Results showed this approach resulted in a control group that was highly credible and acceptable to patients. This approach can be an effective and practical guide for developing high-quality control groups in trials of behavioral interventions.

Placebo in Surgical Research: A Case-Based Ethical Analysis and Practical Consequences

Placebo is a form of simulated medical treatment intended to deceive the patient/subject who believes that he/she received an active therapy. In clinical medicine, the use of placebo is allowed in particular circumstances to assure a patient that he is taken care of and that he/she receives an active drug, even if this is not the case. In clinical research placebo is widely used, as it allows a baseline comparison for the active intervention. If the use of placebo is highly regulated in pharmacological trials, surgery studies have a series of particularities that make its use extremely problematic and regarded less favorably. The purpose of this paper is to present three famous cases of placebo use in surgical trials and to perform an ethical analysis of their acceptability using the Declaration of Helsinki as a main regulatory source.