Nocebo in motor neuron disease: systematic review and meta-analysis of placebo-controlled clinical trials

The Nocebo Effect

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

The relationship between expectancy, anxiety, and the nocebo effect: a systematic review and meta-analysis with recommendations for future research

Despite the theoretical prominence of expectancy and anxiety as potential mechanisms of the nocebo effect, not all studies measure expectancy and/or anxiety, and there are inconsistent findings among those that do. The present study sought to systematically review and meta-analyse available data to evaluate the relationship between expectancy, anxiety and the nocebo effect. The two key questions were: (1) whether nocebo manipulations influence expectancy and anxiety; and (2) whether expectancy and anxiety are associated with the subsequent nocebo effect. Fifty-nine independent studies (n = 3129) were identified via database searches to 1st August 2021. Nocebo manipulations reliably increased negative expectancy with a large effect (g = .837) and state anxiety with a small effect (g = .312). Changes in expectancy and state anxiety due to the nocebo manipulation were associated with larger nocebo effects (r = .376 and .234, respectively). However, there was no significant association between dispositional anxiety and the nocebo effect. These findings support theories that rely on situationally-induced expectancy and anxiety, but not dispositional anxiety, to explain nocebo effects. Importantly, being malleable, these findings suggest that interventions that target maladaptive negative expectancies and state anxiety could be beneficial for reducing the harm nocebo effects cause across health settings. Recommendations for future research are discussed.

Nocebo Response in Attention Deficit Hyperactivity Disorder: Meta-Analysis and Meta-Regression of 105 Randomized Clinical Trials

OBJECTIVE

To determine nocebo response in ADHD, identify covariates modifying nocebo response, and study the relationship between nocebo response and drug safety.

METHOD

Systematic review of randomized, double-blind, placebo-controlled clinical trials (RCT) investigating the efficacy and safety of pharmacological interventions for ADHD patients. The influence of covariates was studied using meta-regression.

RESULTS

A total of 105 studies with 8,743 patients in placebo arms were included. Slightly over half (55.5%) of the patients experienced adverse events (AE) while receiving placebo. Nocebo response was associated positively with age, treatment length and method for collecting AEs. Studies with the largest nocebo response showcased the greatest drug response and the best outcome for drug safety.

CONCLUSION

Nocebo response in ADHD RCTs is remarkable, showing a positive relationship with drug response, and a negative relationship with drug safety.

Maximizing placebo response in neurological clinical practice

The placebo effect is a widely recognized phenomenon in clinical research, with a negative perception that it could hide the "true" drug effect. In clinical care its positive potential to increase known drug effects has been neglected for too long. The placebo and nocebo responses have been described in many neurologic disorders such as Parkinson's, Huntington's and Alzheimer's diseases, restless leg syndrome, tics, essential tremor, dystonia, functional movement disorders, neuropathic pain, headaches, migraine, amyotrophic lateral sclerosis, myasthenia gravis, chronic inflammatory demyelinating polyneuropathy, multiple sclerosis and epilepsy. Knowledge regarding placebo mechanisms and their consequences on clinical outcome have greatly improved over the last two decades. This evolution has led to reconsiderations of the importance of placebo response in the clinic and has given several clues on how to improve it in daily practice. In this chapter, we first illustrate "why," e.g. the reasons (relevance to clinical practice, help in differential diagnosis/treatment of psychogenic movements, clinical impact, proven neurobiological grounds, health economic potential), and "how," e.g. the means (increase patients' knowledge, increase learning, improve patient-doctor relationship, increase Hawthorne effect, increase positive/decrease negative expectations (the Rosenthal effect), personalize placebo response), the placebo should be maximized (and nocebo avoided) in neurological clinical practice. Future studies regarding more specific neurobiological mechanisms will allow a finer tuning of placebo response in clinical practice. The use of placebo in clinical practice raises ethical issues, and a recent expert consensus regarding placebo use in the clinic is a first step to future guidelines necessary to this field.

Nocebo and lessebo effects

The power of placebos is commonly associated with the placebo effect. In contrast, detrimental effects related to the use of a placebo are little studied and less well recognized. This chapter covers the nocebo and lessebo effects defined, respectively, as expectation of harm in the form of adverse events in a placebo arm and reduction of therapeutic benefit due to the uncertainty of being allocated to placebo. The lessebo effect is a more recent concept and has been described only in depression, schizophrenia and Parkinson's disease. The nocebo response was evaluated in many neurological diseases, including epilepsy, multiple sclerosis, Parkinson's disease, Alzheimer's disease, restless leg syndrome, among others. Meta-analyses of randomized controlled trials in these conditions reveal a significant variability of the magnitude of the nocebo response and that factors related to study design, study participants or neurological disease can be associated with a nocebo response, although with the opposing findings across conditions. The knowledge about neurobiological mechanisms of the nocebo effect is poor for neurological diseases, and most of the information has been generated in pain. Functional neuroimaging suggests the existence of a distinct network for the anticipation and the experience of a hyperalgesia nocebo response. Different types of neurotransmitters have been involved, including cholecystokinin, dopamine and opioids. Recognizing the potential impact of nocebo and lessebo effects, mitigating strategies are in development with application to clinical research and clinical practice, such as a contextualized informed consent process, alternative study designs and enhancement of patient-physician communication.

Nocebo effect in myasthenia gravis: systematic review and meta-analysis of placebo-controlled clinical trials

Nocebo refers to the adverse events (AEs) experienced when taking a placebo drug and is believed to be a centrally mediated process. We sought to examine the AEs following placebo administration in Randomised Controlled Trials (RCTs) for Myasthenia Gravis (MG) patients. A systematic literature search was performed on Medline and Web of Science for RCTs for MG pharmacological treatments. We assessed the number of placebo-treated patients reporting at least one AE and the number of dropouts because of AEs. Data were extracted from six RCTs fulfilling the search criteria. Four out of five placebo-treated participants (80.1%) reported at least one AE and one in 40 (2.4%) discontinued placebo treatment because of AE. All patients participating in the MG trials reported similar AEs independent of the study arm to which they belonged (placebo or active treatment). This meta-analysis demonstrates a low nocebo dropout rate in MG compared to central nervous system disorders.

Safety, Tolerability, and Nocebo Phenomena During Transcranial Magnetic Stimulation: A Systematic Review and Meta-Analysis of Placebo-Controlled Clinical Trials

BACKGROUND

The methodology used for the application of repetitive transcranial magnetic stimulation (TMS) is such that it may induce a placebo effect. Respectively, adverse events (AEs) can occur when using a placebo, a phenomenon called nocebo. The primary aim of our meta-analysis is to establish the nocebo phenomena during TMS. Safety and tolerability of TMS were also studied.

METHODS

After a systematic Medline search for TMS randomized controlled trials (RCTs), we assessed the number of patients reporting at least one AE and the number of discontinuations because of AE in active and sham TMS groups.

RESULTS

Data were extracted from 93 RCTs. The overall pooled estimate of active TMS and placebo treated patients who discontinued treatment because of AEs was 2.5% (95% CI 1.9%-3.2%) and 2.7% (95% CI 2.0%-3.5%), respectively. The pooled estimate of active TMS and placebo treated patients experiencing at least one AE was 29.3% (95% CI 19.0%-22.6%) and 13.6% (95% CI 11.6%-15.8%), respectively, suggesting that the odds of experiencing an AE is 2.60 times higher (95% CI 1.75-3.86) in the active treatment group compared to placebo (p < 0.00001). The most common AE was headache, followed by dizziness. Secondary meta-analyses in depression and psychotic disorders showed that the odds of experiencing an AE is 3.98 times higher (95% CI 2.14-7.40) and 2.93 times higher (95% CI 1.41-6.07), respectively, in the active treatment groups compared to placebo.

CONCLUSIONS

TMS is a safe and well-tolerated intervention. Nocebo phenomena do occur during TMS treatment and should be acknowledged during clinical trial design and daily clinical practice.

Rapid overview of systematic reviews of nocebo effects reported by patients taking placebos in clinical trials

Background

Trial participants in placebo groups report experiencing adverse events (AEs). Existing systematic reviews have not been synthesized, leaving questions about why these events occur as well as their prevalence across different conditions unanswered.

Objectives

To synthesize the evidence of prevalence of AEs in trial placebo groups across different conditions.

To compare AEs in trial placebo groups with AEs reported in untreated groups within a subset of randomized trials.

Search methods

We searched PubMed for records with the word “nocebo” in the title and “systematic” in any field. We also contacted experts and hand-searched references of included studies.

Study eligibility

We included any systematic review of randomized trials where nocebo effects were reported. We excluded systematic reviews of non-randomized studies.

Participants and interventions

We included studies in any disease area.

Study appraisal and synthesis methods

We appraised the quality of the studies using a shortened version of the Assessment of Multiple Systematic Reviews tool (AMSTAR) tool. We reported medians and interquartile ranges (IQRs) of AEs. Among the trials within the review that included untreated groups, we compared the prevalence of AEs in untreated groups with the prevalence of AEs in placebo groups.

Results

We identified 20 systematic reviews. These included 1271 randomized trials and 250,726 placebo-treated patients. The median prevalence of AEs in trial placebo groups was 49.1% (IQR 25.7–64.4%). The median rate of dropouts due to AEs was 5% (IQR 2.28–8.4%). Within the 15 of trials that reported AEs in untreated groups, we found that the AE rate in placebo groups (6.51%) was higher than that reported in untreated groups (4.25%).

Limitations

This study was limited by the quality of included reviews and the small number of trials that included untreated groups.

Conclusions and implications of key findings

AEs in trial placebo groups are common and cannot be attributed entirely to natural history. Trial methodologies that reduce AEs in placebo groups while satisfying the requirement of informed consent should be developed and implemented.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-3042-4) contains supplementary material, which is available to authorized users.

Incidence of Placebo Adverse Events in Randomized Clinical Trials of Targeted and Immunotherapy Cancer Drugs in the Adjuvant Setting: A Systematic Review and Meta-analysis

IMPORTANCE

Several reports have associated the placebo effect with objective response and improvement of a clinical condition in oncology, but only a few studies have analyzed the adverse events (AEs) in the placebo groups of the clinical trials.

OBJECTIVE

To determine the incidence of placebo AEs reported in randomized clinical trials of modern cancer drugs in the adjuvant setting.

DATA SOURCES

Based on the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline, a systematic literature search of English-language publications from January 1, 2000, through April 15, 2018, was performed using MEDLINE (PubMed). The following search terms were used to retrieve all trials from the PubMed library: adjuvant, maintenance, consolidation, and placebo, in addition to specific cancer type-related keywords.

STUDY SELECTION

A double-blind, randomized, placebo-controlled, phase 3 design was mandatory for study inclusion. Only studies enrolling patients who had undergone macroscopically complete resections were included. No other anticancer treatments in addition to placebo were allowed in the control group. Only trials involving a targeted therapy (tyrosine kinase, BRAF, or MEK inhibitors) or immunotherapy-related drugs were included. Trials using chemotherapy, interferon, and endocrine therapy were excluded. Two authors (D.H.E. and F.D.W.) independently reviewed the studies for inclusion.

DATA EXTRACTION AND SYNTHESIS

Data were extracted by investigators, and random-effects meta-analysis was performed to estimate the proportion of grade 3 to 4 placebo AEs in the included studies.

MAIN OUTCOMES AND MEASURES

Incidence of grade 3 to 4 placebo AEs in the placebo groups.

RESULTS

Of 731 studies screened, 10 eligible trials were found including 4 tumor types (melanoma, non-small cell lung cancer, gastrointestinal stromal tumor, and renal cell carcinoma). Overall, 11 143 patients (6270 [56.3%] in the treatment group with mean [SD] age of 55.6 [4.2] years and 4873 patients [43.7%] in the placebo group with mean [SD] age of 55.9 [4.3] years) were included. The mean incidence of any-grade placebo AEs was 85.1% (95% CI, 79.2%-91.0%). The most frequent (mean [SD]) grade 3 to 4 placebo AEs in patients were hypertension (2.8% [2.2%]), fatigue (1.0% [0.9%]), and diarrhea (0.8% [0.6%]). The overall, random-effects pooled incidence of grade 3 to 4 placebo AEs was 18% (95% CI, 15%-21%), with a high level of heterogeneity (I2 = 86%). Frequency of grade 3 to 4 placebo AEs was found to be correlated in the treatment and placebo groups (ρ = 0.7; P = .03). Mean study drug discontinuation owing to placebo AEs was 3.9% (95% CI, 2.7%-5.2%).

CONCLUSIONS AND RELEVANCE

Placebo administration was associated with a substantial incidence of grade 3 to 4 placebo AEs in modern cancer adjuvant trials. This finding should be considered by investigators, sponsors, regulatory authorities, and patient support groups.