Placebo and its evil twin, nocebo

Risk factors associated with nocebo effects: A review of reviews

Objective

This meta-review aims to identify and categorize the risk factors that are associated with nocebo effects. The nocebo effect can exert a negative impact on treatment outcomes and have detrimental outcomes on health. Learning more about its potential predictors and risk factors is a crucial step to mitigating it.

Methods

Literature review studies about the risk factors for nocebo effects were searched through five databases (PubMed, Scopus, The Cochrane Library, PsycINFO, and Embase) and through grey literature. Methodological validity and risk of bias were assessed. We conducted a thematic analysis of the results of the forty-three included reviews.

Results

We identified nine categories of risk factors: prior expectations and learning; socio-demographic characteristics; personality and individual differences; neurodegenerative conditions; inflammatory conditions; communication of information and patient-physician relationship; drug characteristics; setting; and self-awareness. We also highlighted the main biochemical and neurophysiological mechanisms underlying nocebo effects.

Conclusions

Nocebo effects arise from expectations of adverse symptoms, particularly when triggered by previous negative experiences. A trusting relationship with the treating physician and clear, tailored treatment instructions can act as protective factors against a nocebo effect. Clinical implications are discussed.

Mind games in dentistry: confounded evidence suggests a substantial nocebo response in dental impaction pain model

DESIGN

A systematic review and metaanalysis of randomized clinical trials (RCTs).

DATA SOURCES

Electronic search was conducted in PubMed, Embase, Scopus, Web of Science and the Cochrane Central Register of Controlled Trials (CENTRAL), on 22 May 2021.

SELECTION CRITERIA

Eligibility criteria included parallel-group placebo-controlled RCTs assessing analgesics after third molar (M3) surgery in healthy patients, reporting the number of patients with at least one drug-related adverse event (AE), and being published in English.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently screened all identified articles against the eligibility criteria, and performed quality assessment and data extraction. Any disagreements were resolved by discussion involving a third reviewer. The primary outcome was the pooled rate of drug-related AEs in placebo and active arms of RCTs assessing analgesic treatment following M3 surgery. Secondary outcome was the drug-related dropout rates in the same setting.

RESULTS

A total of 50 RCTs in 47 articles were included in the analyses. The pooled rates of patients with AE ≥ 1 in the placebo and active arms were 22.8% and 20.6%, respectively. The pooled drug-related dropout rates in the placebo and active arms were 0.24% and 0.08%, respectively. There were no significant risk differences in patients with AE ≥ 1 and drug-related dropouts (p = 0.61 and p = 0.94; respectively). High statistical heterogeneity was found for the proportion of patients with AE ≥ 1 (I2 = 79.7%, p < 0.001), but not for drug-related dropout rates (I2 = 0%, p = 1.00).

CONCLUSION

Patients in the placebo arm reported AEs at a similar frequency as patients receiving active treatment, suggesting that most analgesic-related AEs after M3 surgery may be attributed to the nocebo phenomenon.

Nocebo response in dentistry: A systematic review and meta-analysis of adverse events in analgesic trials of third molar removal

BACKGROUND

The nocebo response refers to the phenomenon where non-specific factors, including negative verbal suggestion and treatment expectations, cause adverse events (AE) following a placebo treatment. Non-specific factors are also likely to influence AE occurrence following administration of active pharmacological treatments.

OBJECTIVE

This meta-analysis aimed to estimate the nocebo response in dentistry by assessing the AEs prevalence in placebo- and active arms of randomised controlled trials (RCTs) assessing analgesic treatment following third molar (M3) surgery.

METHODS

A systematic search was performed in PubMed, Embase, Scopus, Web of Science and the Cochrane Central Register of Controlled Trials. Eligible studies had to report the number of patients experiencing at least one drug-related AE (patients with AE ≥ 1) separately for the active and placebo arms. The proportion of patients with AE ≥ 1 and drug-related dropouts were pooled, and risk differences (RDs) between patients in the placebo- and active arm were calculated.

RESULTS

In 50 independent RCTs of 47 identified articles, the pooled rates of patients with AE ≥ 1 were 22.8% in the placebo arm and 20.6% in the active arm. The pooled rates of drug-related dropout were 0.24% in the placebo arm and 0.08% in the active arm. There were no significant RDs in patients with AE ≥ 1 and drug-related dropouts.

CONCLUSION

These results show that patients in the placebo arm reported AEs to the same extent as patients receiving active treatment, suggesting that most AEs in analgesic medication following M3 surgery may be attributed to the nocebo phenomenon.

What is the nocebo effect and does it apply to dentistry? A narrative review

Background

Evidence for the nocebo effect, a phenomenon characterised by suboptimal treatment efficacy, worsening of symptoms, or the occurrence of adverse events caused by an individual’s negative treatment expectations, is growing across a multitude of medical fields. However, little attention has been paid to patients’ negative expectations and the nocebo effect within dentistry.

Aim

This review summarises essential evidence of the nocebo phenomenon especially in relation to pain and drug administration. Subsequently, an overview of the current evidence of the nocebo phenomenon in the dental field is presented.

Methods

A PubMed search was performed using keywords related to “nocebo,” “placebo,” “expectations,” and “dentistry.” In addition to the articles selected from the search, placebo/nocebo researchers and dental researchers added important references from their respective fields.

Results

Although research on the nocebo effect in dentistry is limited, available current evidence suggests that the factors, which is related to the nocebo effect are likely to play a role in dental practice.

Conclusion

Preliminary evidence from the review warrants further investigation into the nocebo effect in dentistry. Finally, based on the general knowledge of the nocebo effect, the review indicates fruitful arrays of research into the nocebo effect in dentistry.

Positive expectations predict improved mental-health outcomes linked to psychedelic microdosing

Psychedelic microdosing describes the ingestion of near-threshold perceptible doses of classic psychedelic substances. Anecdotal reports and observational studies suggest that microdosing may promote positive mood and well-being, but recent placebo-controlled studies failed to find compelling evidence for this. The present study collected web-based mental health and related data using a prospective (before, during and after) design. Individuals planning a weekly microdosing regimen completed surveys at strategic timepoints, spanning a core four-week test period. Eighty-one participants completed the primary study endpoint. Results revealed increased self-reported psychological well-being, emotional stability and reductions in state anxiety and depressive symptoms at the four-week primary endpoint, plus increases in psychological resilience, social connectedness, agreeableness, nature relatedness and aspects of psychological flexibility. However, positive expectancy scores at baseline predicted subsequent improvements in well-being, suggestive of a significant placebo response. This study highlights a role for positive expectancy in predicting positive outcomes following psychedelic microdosing and cautions against zealous inferences on its putative therapeutic value.

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.