Can knowledge of Placebo and Nocebo Mechanisms Help Improve Randomized Clinical Trials?

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

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

The Biology of Placebo and Nocebo Effects on Experimental and Chronic Pain: State of the Art

(1) Background: In recent years, placebo and nocebo effects have been extensively documented in different medical conditions, including pain. The scientific literature has provided strong evidence of how the psychosocial context accompanying the treatment administration can influence the therapeutic outcome positively (placebo effects) or negatively (nocebo effects). (2) Methods: This state-of-the-art paper aims to provide an updated overview of placebo and nocebo effects on pain. (3) Results: The most common study designs, the psychological mechanisms, and neurobiological/genetic determinants of these phenomena are discussed, focusing on the differences between positive and negative context effects on pain in experimental settings on healthy volunteers and in clinical settings on chronic pain patients. Finally, the last section describes the implications for clinical and research practice to maximize the medical and scientific routine and correctly interpret the results of research studies on placebo and nocebo effects. (4) Conclusions: While studies on healthy participants seem consistent and provide a clear picture of how the brain reacts to the context, there are no unique results of the occurrence and magnitude of placebo and nocebo effects in chronic pain patients, mainly due to the heterogeneity of pain. This opens up the need for future studies on the topic.

Examining the Nocebo Effect in Trials of Neuromodulators for Use in Disorders of Gut-Brain Interaction

BACKGROUND AND AIMS

Nocebo effects are thought to influence the rate of reported adverse events (AEs) and subject withdrawal in both the treatment and placebo groups of randomized clinical trials (RCTs). Neuromodulators are commonly prescribed to treat disorders of gut-brain interaction (DGBIs), but adherence to these medications is often limited by side effects such as headache, dry mouth, fatigue, and altered bowel habits. We performed a systematic review and meta-analysis to assess the proportion and risk difference of patients who experienced side effects leading to withdrawal in the placebo arm versus the treatment arm of RCTs of neuromodulators for DGBIs. We also sought to estimate the risk of developing any AE in the placebo arm of these studies as well as the rate of specific individual adverse events.

METHODS

We searched MEDLINE, Embase, Web of Science Core Collection, and the Cochrane Central Register of Controlled Trials Searches to identify RCTs that included terms for DGBIs and for commonly prescribed neuromodulators. We calculated pooled proportions of patients experiencing an AE leading to withdrawal in the active treatment group versus the placebo group with 95% confidence intervals (CI), the pooled proportions of patients experiencing any adverse event, the pooled proportions of patients experiencing specific adverse events such as dizziness and headache, the pooled proportions of patients experiencing severe adverse events and corresponding pooled risk differences with 95% CIs.

RESULTS

There were 30 RCTs included representing 2284 DGBI patients. 27 RCTs reported data on AEs leading to withdrawal. The pooled proportion of total patients with AEs leading to withdrawal in the placebo group was 4% (95% CI 0.02 - 0.04). The pooled proportion of patients with AEs leading to withdrawal who received neuromodulators was 9% (95% CI 0.06-0.13). In the 12 studies reporting data on patients experiencing at least one AE, the pooled proportion of patients experiencing any adverse event in the placebo group was 18% (95% CI 0.08 - 0.30), compared to 43% (95% CI 0.24 - 0.63) in the neuromodulator group. Thus, approximately 44% of the rate of withdrawal (0.04/0.09) and 42% of the rate reporting any side effects (0.18/0.43) in the neuromodulator group may be attributed to nocebo effects in the right context. Subgroup analysis by sex, medication class, risk of bias, and specific DGBIs revealed differing withdrawal rates. There was no statistically significant difference in patients experiencing individual AEs of dizziness, headache or diarrhea. Rates of dry mouth, fatigue and constipation were higher in treatment groups compared to placebo groups.

CONCLUSION

Patients with DGBIs in RCTs randomized to placebo groups frequently experience AEs and AEs that lead to withdrawal consistent with a strong nocebo effect. Non-specific AEs such as dizziness, headaches and diarrhea occurred similarly in patients receiving placebo compared to those receiving neuromodulators.

Response and Adverse Event Rates With Placebo in Gastroparesis: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

Multiple drugs have been used to treat gastroparesis symptoms, yet their therapeutic benefits are poorly understood partly due to lack of insight into response and adverse event rates with placebo in randomized controlled trials (RCTs). We evaluated these issues systematically in drug trials for gastroparesis.

METHODS

We searched the medical literature through August 2, 2022 to identify RCTs comparing active drug with placebo in patients with gastroparesis. We assessed placebo response rates according to at least one of the following endpoints: improvement according to a composite outcome, nausea, vomiting, abdominal pain, bloating, or fullness, as well as total adverse events, and adverse events leading to withdrawal. We extracted data as intention-to-treat analyses with dropouts assumed to be treatment failures. We pooled placebo response and adverse event rates using a random effects model and expressed as proportions with 95% confidence intervals (CIs).

RESULTS

Thirty-five studies were eligible. Among 23 trials reporting a composite endpoint of improvement, the pooled placebo response rate was 29.3% (95% CI, 23.7%-35.2%). Pooled placebo response rates were higher in idiopathic compared with diabetic gastroparesis (34.2% vs 28.1%), among trials that did not use validated symptom questionnaires (31.2% vs 27.4%), and in RCTs of shorter duration (<4 weeks, 32.6% vs ≥9 weeks, 23.2%). Adverse events occurred in 33.8% (95% CI, 26.4%-41.8%) of patients with placebo, in 27 trials, and were less common in idiopathic compared with diabetic gastroparesis (17.9% vs 43.4%), trials of shorter duration (<4 weeks, 33.7% vs ≥9 weeks, 40.7%), and trials with lower randomization ratios of active drug to placebo (1:1, 26.7% vs 3:1, 50.5%).

CONCLUSIONS

This meta-analysis assessed placebo response and adverse event rates in gastroparesis. To accurately assess therapeutic gain, future trials should be a minimum of 8 weeks duration, use validated questionnaires, and distinguish gastroparesis subtypes.

Adverse events in trials of licensed drugs for irritable bowel syndrome with constipation or diarrhea: Systematic review and meta-analysis

BACKGROUND

Nocebo effects occurring in patients receiving placebo frequently impact on adverse events reported in randomized controlled trials (RCTs) in irritable bowel syndrome (IBS). Therefore, we conducted a systematic review and meta-analysis to assess the proportion of patients randomized to placebo or active drug experiencing any adverse event in trials of licensed drugs for IBS with constipation (IBS-C) or diarrhea (IBS-D), and to estimate the risk of developing adverse events among patients randomized to placebo.

METHODS

We searched MEDLINE, EMBASE CLASSIC and EMBASE, and the Cochrane central register of controlled trials (through June 2021) to identify RCTs comparing licensed drugs with placebo in adults with IBS-C or IBS-D. We generated Forest plots of pooled adverse event rates in both active drug and placebo arms and pooled risk differences (RDs) with 95% confidence intervals (CIs).

KEY RESULTS

There were 21 RCTs of licensed drugs versus placebo in IBS-C (5953 patients placebo) and 17 in IBS-D (3854 patients placebo). Overall, 34.9% and 46.9% of placebo patients in IBS-C and IBS-D trials, respectively, developed at least one adverse event, with a statistically significantly higher risk of any adverse event and withdrawal due to an adverse event with active drug. In IBS-C and IBS-D trials, rates of each individual adverse event were generally higher with active drug. However, in IBS-C trials, only diarrhea or headache was significantly more common with active drug (RD 0.066 (95% CI 0.043-0.088) and RD 0.011 (95% CI 0.002-0.021), respectively), and in IBS-D trials only constipation, nausea, or abdominal pain (RD 0.096 (95% CI 0.054-0.138), 0.014 (95% CI 0.002-0.027), and 0.018 (95% CI 0.002-0.034), respectively).

CONCLUSIONS & INFERENCES

Patients with IBS randomized to placebo have a high risk of reporting adverse events, which might relate to both nocebo and non-nocebo factors. Although patients' expectations and psychosocial factors may be involved, further understanding of the mechanisms are important to control or optimize these effects in RCTs, as well as in clinical practice.

Safety of transcranial magnetic stimulation in unipolar depression: A systematic review and meta-analysis of randomized-controlled trials

BACKGROUND

To study the safety and patients' tolerance of transcranial magnetic stimulation (TMS), we conducted a systematic review and meta-analysis of the major depressive disorder population.

METHODS

Our study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched the literature published before April 30th, 2021 and performed a random-effects meta-analyses which included drop-out due to adverse events, serious adverse events and other non-serious adverse events as primary and secondary outcomes.

RESULTS

A total of 53 randomized sham-controlled trials with 3,273 participants were included. There was no increased risk of drop-out due to an adverse event (active TMS intervention group=3.3%, sham TMS intervention group=2.3%, odds ratio = 1.30, 95% CI= 0.78-2.16, P = 0.31) or a serious adverse event (active TMS intervention group=0.9%, sham TMS intervention group=1.5%, odds ratio = 0.67, 95% CI= 0.29-1.55, P = 0.35). Our findings suggest that TMS intervention may significantly increase the risk of non-serious adverse events including: headaches (active TMS intervention group=22.6%, sham TMS intervention group=16.2%, odds ratio = 1.48, 95% CI= 1.15-1.91, P = 0.002), discomfort (active TMS intervention group=10.9%, sham TMS intervention group=5.0%, odds ratio 1.98, 95% CI= 1.22-3.21, P = 0.006) and pain (active TMS intervention group=23.8%, sham TMS intervention group=5.2%, odds ratio= 8.09, 95% CI= 4.71-13.90, P < 0.001) at the stimulation site, but these non-serious events were mostly mild and transient after TMS treatment.

CONCLUSIONS

These findings provide evidence for the safety and patients' tolerance of transcranial magnetic stimulation technique as an alternative monotherapy or as an add-on treatment for major depressive disorder.

Myths and Truths about Placebo Effect in Rehabilitation for Musculoskeletal Pain

This commentary provides the authors' point of view about the biopsychosocial perspective of placebo effect on musculoskeletal pain in the rehabilitation field.

Demonstration of central conduction time and neuroplastic changes after cervical lordosis rehabilitation in asymptomatic subjects: a randomized, placebo-controlled trial

A randomized controlled study was conducted to evaluate the effect of rehabilitation of the cervical sagittal configuration on sensorimotor integration and central conduction time in an asymptomatic population. Eighty (32 female) participants with radiographic cervical hypolordosis and anterior head translation posture were randomly assigned to either a control or an experimental group. The experimental group received the Denneroll cervical traction while the control group received a placebo treatment. Interventions were applied 3 × per week for 10 weeks. Outcome measures included radiographic measured anterior head translation distance, cervical lordosis (posterior bodies of C2–C7), central somatosensory conduction time (latency) (N13–N20), and amplitudes of potentials for spinal N13, brainstem P14, parietal N20 and P27, and frontal N30. Outcomes were obtained at: baseline, after 10 weeks of intervention, and at 3 months follow up. After 10 weeks and 3-months, between-group analyses revealed statistically significant differences between the groups for the following measured variables: lordosis C2–C7, anterior head translation, amplitudes of spinal N13, brainstem P14, parietal N20 and P27, frontal N30 potentials (P < 0.001), and conduction time N13–N20 (P = 0.004). Significant correlation between the sagittal alignment and measured variables were found (P < 0.005). These findings indicate restoration of cervical sagittal alignment has a direct influence on the central conduction time in an asymptomatic population.

The placebo phenomenon and the underlying mechanisms

The clinical role of the placebo effect is a topic of increasing interest for the scientific community. Focus is shifting from the inert role of placebos in randomized controlled trials (RCTs) to potential effects in clinical applications, since the phenomenon is thought to be inherent in routine clinical practice, affecting therapy success rates. Mediation of the mind-brain-body relationship involves both psychosocial and neurobiological factors, the interaction of which comprises the placebo mechanisms. Psychosocial factors include environmentally induced expectations, reward expectations, and even conditioned responses to certain stimuli. Expectations also depend on previous experience of the patient with a similar procedure and can affect future responses. Moreover, the supportive bedside behavior of the clinician and the positive framing of information provided to the patient have proven to be of great importance, setting the foundations for reconsideration of standardized practices. Neurobiological mechanisms mediate these effects through neurotransmitter and neuromodulator pathways. The best understood mechanisms are those regulating non-opioid- and opioid-mediated analgesic responses that implicate specific brain regions of pain control and activation of endogenous opioids. Other responses concern, among others, hormonal control, motor performance, and antidepressant responses. Although mechanisms underlying placebo responses are not as yet completely elucidated, there is substantial evidence suggesting that placebo effects are indicative of healthy functioning of intact brain structures and occur through actual functional changes, and are not simply subjective symptom reports. These effects can be utilized in treatment optimization while maintaining an ethical and respectful manner toward the patient and the standardized disclosure procedures.

Nocebo phenomena may be enhanced in aging: Implications for clinical practice

Nocebo effects, denoting unfavourable outcomes after a medical intervention because of negative expectations rather than a direct pharmacologic action, are an important cause of dropout from clinical trials and non-adherence to medication, and may be especially pertinent for older adults. Several characteristics of aging individuals and their medical care have a potential to augment nocebo susceptibility, such as depression and anxiety, neurodegenerative diseases and chronic pain states, adverse healthcare experiences, generic drug use, age-related stereotypes, and strained patient-physician communication. Nocebo-related research in older adults is hindered by under-representation in clinical trials, medical complexity of geriatric patients, and lack of validated tools to accurately assess susceptibility and efficacy of preventive efforts.

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

Background

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

Objectives

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

Conclusion

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

Issues Impacting Adverse Event Frequency and Severity: Differences Between Randomized Phase 2 and Phase 3 Clinical Trials for Lasmiditan

Objective

We explore factors that may have contributed to differences in treatment‐emergent adverse events in the phase 2 and phase 3 lasmiditan clinical trials.

Background

Phase 2 and phase 3 trials showed that the centrally penetrant 5‐HT_1F agonist, lasmiditan, was effective; higher frequency and severity of adverse events (AEs) were seen in phase 2.

Methods

This work represents a hybrid of a review of primary documents and study reports with additional post hoc analyses. Protocols, informed consents, data collection forms, and methodologies were reviewed. This information was supplemented by results from the clinical study reports and post hoc analyses of individual patient data from each trial.

Results

For lasmiditan 100 and 200 mg, in phase 2, the incidence of ≥1 AE was 72‐86% (26% severe), while in phase 3 was 36‐43% (2% severe). The most common AEs in all studies were CNS‐related. The phase 2 consent form was more descriptive of AEs than phase 3. In phase 2, patients recorded AEs and severity in a paper diary that warned about drowsiness and dizziness. In phase 3, patients recorded in electronic diaries whether they experienced unusual feelings after dosing with lasmiditan that they had not felt with a migraine before, and were contacted to determine if an AE had occurred. In phase 2, the AE Schwindel was variably translated from German as “vertigo” or “dizziness,” while phase 3 vertigo cases were queried to ensure there was a sensation of rotation or movement. History of recurrent dizziness and/or vertigo was exclusionary in phase 3.

Conclusions

This work illustrates how informed consent wording, AE collection methods, translation, exclusion criteria, and other factors may be important determinants for reporting of the frequency and severity of AEs in clinical trials.

Adverse Events and Nocebo Effects in Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND AND AIMS

Nocebo effects, adverse outcomes occurring in patients receiving inert therapy, contribute to adverse event [AE] reporting in randomized controlled trials [RCTs]. High placebo AE rates may result in inaccurate estimation of treatment-related AEs. We estimate the pooled rate of AEs in patients randomized to placebo compared to active therapy in inflammatory bowel disease [IBD] RCTs.

METHODS

MEDLINE, EMBASE and CENTRAL were searched to March 1, 2017 for RCTs of conventional medical therapies for Crohn's disease [CD] or ulcerative colitis [UC]. Rates of AEs, serious AEs [SAEs], AE-related trial withdrawal, infections and worsening IBD were pooled using a random-effects model.

RESULTS

We included 124 CD [n = 26 042] and 71 UC RCTs [n = 16 798]. The pooled placebo AE rate was 70.6% (95% confidence interval [CI]: 65.3%, 75.4%) and 54.5% [47.8%, 61.1%] in CD and UC RCTs, respectively. There was no significant risk difference [RD] in AE, SAE or AE-related withdrawal rates between CD patients receiving placebo or active drug. A 1.6% [95% CI: 0.1%, 3.1%] increase in AE rates was observed among UC patients randomized to active therapy. Patients receiving active therapy had a higher risk of infection (RD 1.0% [95% CI: 0.4%, 1.7%] for CD, 2.9% [95% CI: 1.4%, 4.4%] for UC) although a lower risk of worsening CD (RD -3.2% [95% CI: -4.8%, -1.5%]) or UC (RD -3.7% [95% CI: -5.7%, -1.8%]).

CONCLUSIONS

AEs are commonly reported by patients randomized to either placebo or active treatment in IBD RCTs. Clinically relevant differences in AE, SAE and AE-related withdrawal were not observed.

Intravenous vortioxetine to accelerate onset of effect in major depressive disorder: a 2-week, randomized, double-blind, placebo-controlled study

This 2-week randomized, double-blind, placebo-controlled fixed-dose study (NCT02919501) explored the potential of accelerating onset of antidepressant efficacy and plasma exposure with single-dose intravenous vortioxetine at oral vortioxetine treatment initiation. Outpatients (ages 18-65 years) with major depressive disorder and a current depressive episode (Montgomery Åsberg Depression Rating Scale total score ≥30) were randomized to an initial single dose of either intravenous vortioxetine 17 mg (n = 27) or intravenous placebo (n = 28), both treatments followed by 2 weeks of oral vortioxetine (10 mg/day). From baseline to day 7, both groups exhibited fast and substantial improvements by approximately 14 Montgomery Åsberg Depression Rating Scale points, with no statistically significant treatment difference for this primary endpoint. Improvements were substantial already within 24 hours, with numerical treatment differences of 1.3 and 1.6 points at days 1 and 3, respectively, in favour of intravenous vortioxetine + oral vortioxetine. Pharmacokinetic data confirmed that intravenous vortioxetine facilitated reaching steady-state plasma concentration within 24 hours. Intravenous vortioxetine + oral vortioxetine was safe and well-tolerated, with nausea as the most common adverse event. This study supported intravenous vortioxetine as a means of rapidly reaching therapeutic vortioxetine blood levels.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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