Human physiological responses to different types of human-dog interactions: A randomised crossover study.

Previous studies of human-dog interventions vary in terms of type of interaction, which is rarely quantified, leading to contradictory findings and limited comparability. To uncover the influence of different types of interactions, the present study investigated if it was possible to detect differences in immediate physiological measurements of healthy humans during different standardised types of interaction with a dog. Thirty-three healthy participants (women = 25, men = 8, >18 years) were exposed to four different test situations with standardised types of interaction intensity with a dog in random order: no dog present (CONTROL), looking at a dog (VISUAL), petting a dog (TACTILE) or performing tricks with a dog (ACTIVE). Each test situation lasted 10 min with a 30-min break between each. Heart rate (HR), heart rate variability (HRV) and skin conductance (tonic level (SCL) and peak counts (SCR)) were continuously recorded. Blood pressure (BP) and salivary cortisol (s-cortisol) were measured before and after each test situation. Linear Mixed Models were applied. HR, HRV, BP, SCL and SCR increased with increased interaction with the dog (for all: p < 0.001). HRV increased with decreased HR (p = 0.002), increased SCL (p = 0.027), and SCR (p < 0.001) depending on the type of interaction. Generally, s-cortisol increased with increased HR (p = 0.042), SCL increased with increased SCR (p < 0.001), and SCR increased with increased HRV (p = 0.013), depending on type of interaction. The physiological measurements HR, HRV, BP, SCL and SCR are influenced by different types of dog interaction, and thus it is important to quantify and report the type of interaction in human-dog interaction studies. (ClinicalTrials.gov ID:NCT04696419).

Mindfulness Effects on Anxiety: Disentangling the Role of Decentering and Treatment Expectations.

Mindfulness interventions have been found to lower anxiety. However, the current literature has not adequately considered the role of its individual components and of placebo effects. In an online experiment using a balanced placebo design, we aimed to disentangle effects of decentering, a key component of mindfulness, and expectations, a key component of placebo effects, on anxiety related to the COVID-19 pandemic. One hundred twenty-eight adults were randomly assigned to one of four groups: placebo/mindful decentering, placebo/sham decentering, sham/mindful decentering, and sham/sham decentering. Instructions were provided using standardized audio instructions. Current anxiety was assessed pre- and postintervention with the Short State version of the State-Trait Anxiety Inventory. Mindful decentering was found to reduce anxiety postintervention, as compared to sham decentering, regardless of induced expectations regarding its effectiveness. Participants in the mindful decentering group also mentioned more decentering-related words than those in the sham decentering group. These findings indicate that a short, standardized, and online mindful decentering intervention can effectively decrease pandemic-related anxiety independently of one's expectations. These findings provide insights into the efficacy of the individual elements of mindfulness, highlighting decentering as an effective active component for anxiety relief. Moreover, these findings suggest that, in a nonclinical sample, individuals can apply mindful decentering with minimal training.

Nocebo belief and attitudes towards side effect disclosure: A general population-based online survey in Europe and North America.

BACKGROUND: With evidence for large nocebo effects in pain, guidelines for nocebo-minimizing strategies regarding side effect disclosure are emerging. While the ethical implications and effectiveness of such strategies have been the subject of investigations, the perspective of healthcare users are missing despite the stakes for patient autonomy. METHODS: In an online survey, 2766 adults (≥18 years) from a general population sample in Europe and North America responded to questions related to nocebo familiarity, nocebo beliefs and attitudes towards side effect disclosure. RESULTS: Only 474 (17%) were familiar with nocebo terminology, while 1379 (50%) were familiar with the concept of nocebo side effects. Belief in nocebo side effects was not well-established; 738 (31%) agreed that side effect information could increase side effect occurrence. Nocebo belief was associated with more negative attitudes towards side effect disclosure and 1962 (73%) indicated that positive framing was an acceptable way of disclosing side effect information. In general, the majority of participants (65-76%) held positive attitudes towards the disclosure of all potential side effects and 2309 (84%) favoured patient autonomy over nonmaleficence. Although the general patterns were similar in the European and North American sample, the latter showed stronger nocebo belief and stronger positive attitudes towards side effect disclosure. CONCLUSIONS: The study found a consistent, moderate association between nocebo belief and attitudes towards nondisclosure, alongside positive attitudes towards the use of framing. Together with the discovered discrepancy between nocebo familiarity and nocebo belief, these findings have implications for the implementation of nocebo education and risk framing strategies. SIGNIFICANCE STATEMENT: This is the first large-scale, general population-based study to contribute to the scientific discussion about nocebo side effects from the perspective of healthcare users. The findings have implications for the discussion on how to handle the medical and ethical problem of nocebo side effects in clinical practice.

The impact of an illness perception conversation on open-label placebo response in knee osteoarthritis: A randomised controlled trial.

OBJECTIVE: To compare the effect of an illness perception conversation (IPC), relative to a research participation conversation (RPC), on 2-week changes in knee pain in patients with knee osteoarthritis. METHOD: This was a randomised single-blind trial. Patients were randomised to two matched conversations. An IP conversation concerning the participant's knee pain-related illness perception (IP) or an RPC concerning the participant's motivation for participating in research. Both conversations were followed by an open-label intraarticular saline injection in the most symptomatic knee. The primary outcome was change in knee pain from baseline to 2 weeks follow-up on a 100 mm visual analogue scale (VAS). Key secondary outcomes included the Knee injury and Osteoarthritis Outcome Score (KOOS) subscales: Activities of daily living (ADL) and Quality of life (QoL). Main analyses were based on the intention-to-treat population using repeated measures mixed effects linear models. RESULTS: 103 patients were randomised to the IPC group (n = 52) and the RPC group (n = 51). VAS knee pain scores changed statistically significantly from baseline to end of treatment in both groups, -13.7 (standard error [SE]: 3.2) in the IPC group and -13.0 (SE: 3.1) in the RPC group with an adjusted between-group difference of -0.7 (95% CI: -8.3 to 6.9; P = 0.85). Likewise, no group differences were seen in KOOS ADL and KOOS QoL. CONCLUSION: A conversation concerning knee pain-related IP did not augment the pain-relieving effect of an open-label placebo injection when compared to a similar control conversation concerning motivations for participating in research. TRIAL REGISTRATION: NCT05225480.

Conclusions Regarding the Role of Expectations in Placebo Analgesia Studies May Depend on How We Investigate It: A Meta-Analysis, Systematic Review, and Proposal for Methodological Discussions.

OBJECTIVE: Expectations are highlighted as a key component in placebo effects. However, there are different approaches to whether and how placebo studies should account for expectations, and the direct contribution has yet to be estimated in meta-analyses. Using different methodological approaches, this meta-analysis and systematic review examines the extent to which expectations contribute to pain in placebo studies. METHODS: The databases PubMed, PsycINFO, Embase, and Web of Science were searched for placebo analgesia mechanism studies with numerical measures of both expectations and pain. Thirty-one studies, comprising 34 independent study populations (1566 subjects: patients and healthy participants) were included. Two meta-analyses were conducted: meta-analysis 1, using study-level data, estimated the effect of expectation interventions without taking measures of expectations into account (expectations assumed); and meta-analysis 2, using individual-level data, estimated the direct impact of participants' expectations on pain (expectations assessed). Risk of bias was assessed using the Cochrane risk-of-bias tool. RESULTS: Meta-analysis 1 showed a moderate effect of expectation interventions over no expectation intervention on pain intensity (Hedges g = 0.45, I2 = 54.19). Based on 10 studies providing individual-level data, meta-analysis 2 showed that expectations predicted pain intensity in placebo and control groups ( b = 0.36, SE = 0.05), although inconsistently across study methodologies. CONCLUSIONS: Participants' expectations contributed moderately to pain in placebo analgesia studies. However, this may largely be influenced by how we measure expectations and how their contribution is conceptualized and analyzed-both within and across studies.

Efficacy of patient education and duloxetine, alone and in combination, for patients with multisystem functional somatic disorder: Study protocol for the EDULOX trial.

BACKGROUND: Multisystem functional somatic disorder is characterized by specific patterns of persistent physical symptoms with a complex biopsychosocial etiology. The disorder can lead to disability and personal suffering. Current treatment options require specialized settings, therefore patients often wait a long time to receive specific treatment. Patient education is considered important in most treatment programs, but has only been investigated sparsely as a stand-alone treatment. Pharmacological treatment is limited to tricyclic antidepressants in low doses with no antidepressant properties. Duloxetine has been found effective in single organ functional disorders. As a treatment for multisystem functional somatic disorder, duloxetine could reduce symptoms and treat comorbid anxiety and depression. It may furthermore enhance the effect of patient education through a hypothesized effect on cognitive functioning. The purpose of the EDULOX trial is to study psycho-EDUcation and duLOXetine alone and in combination. METHODS: This is a nested study design. The parent trial "EDULOX1" (n = 424) will compare a patient education program with enhanced usual care in an open-labelled, randomized controlled trial. In addition to this, eligible participants will furthermore receive either duloxetine or active placebo in the nested, double-blinded, randomized controlled trial, "EDULOX2" (n = 212). Patient and clinician reported outcomes will be collected through questionnaires. CONCLUSION: The EDULOX trial may establish evidence for treatments applicable for the majority of patients with multisystem functional somatic disorder. If effective, duloxetine would be a more tolerable pharmacological treatment option that can target comorbid depression and anxiety, and potentially boost the effect of patient education. Trial registration number The study is registered at www. CLINICALTRIALS: gov (NCT06232473) and the internal list of research projects at the Region of Central Denmark (Case number 1-16-02-305-23). Approval from the Danish Medical Research Ethics Committees (Case number: 2212291) and the Danish Medicines Agency was obtained under EudraCT Number: 2022-002780-30 and Sponsor's Protocol Code Number: 9515.

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

BACKGROUND AND OBJECTIVES: In Parkinson's disease (PD) patients, verbal suggestions have been shown to modulate motor and clinical outcomes in treatment with subthalamic deep brain stimulation (DBS). Furthermore, DBS may alleviate pain in PD. However, it is unknown if verbal suggestions influence DBS' effects on pain. METHODS: Twenty-four people with PD and DBS had stimulation downregulated (80-60 to 20%) and upregulated (from 20-60 to 80%) in a blinded manner on randomized test days: (1) with negative and positive suggestions of pain for down- and upregulation, respectively, and (2) with no suggestions to effect (control). Effects of DBS and verbal suggestions were assessed on ongoing and evoked pain (hypertonic saline injections) via 0-10 numerical rating scales along with motor symptoms, expectations, and blinding. RESULTS: Stimulation did not influence ongoing and evoked pain but influenced motor symptoms in the expected direction. Baseline and experimental pain measures showed no patterns in degree of pain. There was a trend toward negative suggestions increasing pain and positive suggestions decreasing pain. Results show significant differences in identical stimulation with negative vs positive suggestions (60% conditions AUC 38.75 vs 23.32, t(13) = 3.10, p < 0.001). Expectations to pain had small to moderate effects on evoked pain. Patients estimated stimulation level correctly within 10 points. CONCLUSION: Stimulation does not seem to influence ongoing and evoked pain, but verbal suggestions may influence pain levels. Patients appear to be unblinded to stimulation level which is an important consideration for future studies testing DBS in an attempted blind fashion.

Placebo analgesia in physical and psychological interventions: Systematic review and meta-analysis of three-armed trials.

BACKGROUND: The magnitude of placebo effects from physical and psychological 'sham' is unknown but could impact efficacy trials and treatment understanding. To quantify placebo effects, this systematic review of three-armed randomised controlled trials (RCTs) of physical and psychological interventions for pain compared outcomes in 'sham' control intervention and non-exposure arms. METHODS: RCTs with treatment, 'sham' control intervention, and non-exposure groups were included, enrolling adults with any pain. A protocol was pre-registered (PROSPERO: CRD42023413324), and twelve databases searched from 2008 to July 2023. Trial methods and blinding were analysed descriptively and risk of bias assessed. Meta-analysis of pain measures at short-, medium- and long-term was performed with random-effects models of standardised mean differences (SMD).Studies were sub-grouped according to control intervention type. RESULTS: Seventeen RCTs were included. The average short-term placebo effect was small (0.21 SMD, 0.1-0.33 95% CI, p = 0.0002, 1440 participants). It showed no heterogeneity (Tau2 = 0.1, I2 = 11%, p = 0.3), preventing meta-regression analyses of effect modifiers. However, sub-group analyses revealed larger placebo effects in manual control interventions compared to disabled devices and miscellaneous control interventions. Overall, placebo analgesia accounted for 39% of treatments' short-term effectiveness. No placebo effects were found at medium-term (7 RCTs, 381 participants) or long-term follow-up (3 RCTs, 173 participants). CONCLUSIONS: The observed placebo analgesia has mechanistic and methodological implications, though its clinical importance may be limited. Control intervention design affects placebo effects, highlighting the importance of considering methodology in RCT interpretation. Review limitations include a small number of long-term studies and sample heterogeneity. SIGNIFICANCE: This systematic review directly quantifies placebo effects from physical and psychological 'sham' control interventions and compares them to treatments' overall effectiveness. By doing so, the review enhances our understanding of placebo effects, their relative contribution in clinical trials, and their susceptibly to trial design. It poses further questions regarding the influence of blinding, participant expectations, and features of the therapeutic context. Overall, the insights provided by this review carry methodological significance and are important for the interpretation and synthesis of efficacy trials in this field.

Placebo analgesia and nocebo hyperalgesia in patients with Alzheimer disease and healthy participants.

ABSTRACT: The role of placebo analgesia and nocebo hyperalgesia in patients with Alzheimer disease (AD) is largely unknown, with only few studies in the area. Therefore, this study aims to investigate to which extent placebo analgesia and nocebo hyperalgesia effects are present in patients experiencing mild-to-moderate AD. Twenty-one patients with AD (test population) and 26 healthy participants (HP; design validation) were exposed to thermal pain stimulation on 3 test days: Lidocaine condition (open/hidden lidocaine administration), capsaicin condition (open/hidden capsaicin administration), and natural history (no treatment), in a randomized, within-subject design. Open lidocaine and open capsaicin were accompanied by verbal suggestions for pain relief and pain increase, respectively. Expected pain and actual pain intensity were measured on a numerical rating scale (0-10). Placebo and nocebo effects were calculated as pain differences in open-hidden lidocaine and capsaicin, respectively, controlled for no treatment. Healthy participants obtained a placebo effect ( P = 0.01) and a trend for a nocebo effect ( P = 0.07). Patients with AD did not obtain a placebo effect ( P = 0.44) nor a significant nocebo effect ( P = 0.86). Healthy participants expected lower and higher pain with open vs hidden lidocaine and capsaicin, respectively ( P < 0.001). The same expectation effects were seen in patients with AD (open vs hidden lidocaine, P = 0.008; open vs hidden capsaicin, P < 0.001). With a well-controlled experimental setting, this study suggests that patients with AD may not experience placebo analgesia effects. Nocebo hyperalgesia effects in patients with AD needs further research. These findings may have implications for the conduction of clinical trials and the treatment of patients with AD in clinical practice.

The desire for side-effect information in pain treatment: an experimental analysis of contextual and individual difference factors.

ABSTRACT: Informing patients about potential side effects of pain treatment is a requirement that protects patients and aids decision making, but it increases the likelihood of unwanted nocebo side effects. If patients do not desire all side-effect information, it may be possible to ethically reduce nocebo effects through authorized concealment of side effects, whereby patients and clinicians engage in shared decision-making to regulate the disclosure of side-effect information. Currently, there is no experimental data clarifying the factors that causally influence desire for side-effect information in pain treatment. In 2 cross-sectional, between-subjects scenario experiments (experiment 1 N = 498, experiment 2 N = 501), 18 to 79-year-old community adults learned about a lower back pain treatment, and potential side-effect severity, frequency, and duration were manipulated. Individual differences in information avoidance were also recorded. In both experiments, participants reported high desire for side-effect information, but the desire was reduced when side effects were described as less severe, less frequent, and participants scored high in information avoidance. Results were not moderated by participants' level of contact with the health care system, chronic health condition, or clinical pain history. Additional analyses indicated that low side-effect severity and frequency lessen desire for side-effect information because these variables reduce belief that side-effect information will be needed in the future and lower feelings of anticipated regret. The experiments identify situational and individual-difference factors that decrease the desire for side-effect information and provide evidence on when and for whom it may be useful for physicians to engage in shared medical decision-making with the goal of reducing nocebo side effects.

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.

Comparison of indirect treatment methods in migraine prevention to address differences in mode of administration.

Aim: Indirect treatment comparisons (ITCs) are anchored on a placebo comparator, and the placebo response may vary according to drug administration route. Migraine preventive treatment studies were used to evaluate ITCs and determine whether mode of administration influences placebo response and the overall study findings. Materials & methods: Change from baseline in monthly migraine days produced by monoclonal antibody treatments (subcutaneous, intravenous) was compared using fixed-effects Bayesian network meta-analysis (NMA), network meta-regression (NMR), and unanchored simulated treatment comparison (STC). Results: NMA and NMR provide mixed, rarely differentiated results between treatments, whereas unanchored STC strongly favors eptinezumab over other preventive treatments. Conclusion: Further investigations are needed to determine which ITC best reflects the impact of mode of administration on placebo.

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.

Oral capsules of tetra-hydro-cannabinol (THC), cannabidiol (CBD) and their combination in peripheral neuropathic pain treatment.

BACKGROUND: Cannabinoids are often prescribed for neuropathic pain, but the evidence-based recommendation is 'weak against'. OBJECTIVES: The aim was to examine the effect of two cannabinoids and their combination in peripheral neuropathic pain. METHODS: This was a randomized, double-blind, trial with treatment arms for cannabidiol (CBD), tetra-hydro-cannabinol (THC), CBD and THC combination (CBD/THC), and placebo in a 1:1:1:1 ratio and flexible drug doses (CBD 5-50 mg, THC 2.5-25 mg, and CBD/THC 5 mg/2.5 mg-50 mg/25 mg). Treatment periods of 8-week duration were proceeded by 1 week for baseline observations. Patients with painful polyneuropathy, post-herpetic neuralgia and peripheral nerve injury (traumatic or surgical) failing at least one previous evidence-based pharmacological treatment were eligible for inclusion. The primary outcome was the change in weekly average of daily pain measured with a numeric rating scale (NRS). Trail Making Test (TMT) was used as one of the tests of mental functioning. RESULTS: In all, 145 patients were included in the study of which 118 were randomized and 115 included in the intention-to-treat analysis. None of the treatments reduced pain compared to placebo (p = 0.04-0.60). Effect sizes as estimated in week 8 (positive values worse and negative better than placebo) were CBD mean 1.14 NRS points (95% CI 0.11-2.19), THC 0.38 (CI -0.65 to 1.4) and CBD/THC -0.12 (-1.13 to 0.89). CONCLUSIONS: CBD, THC and their combination did not relieve peripheral neuropathic pain in patients failing at least one previous evidence-based treatment for neuropathic pain.

Social communication pathways to COVID-19 vaccine side-effect expectations and experience.

OBJECTIVE: Negative beliefs about medication and vaccine side-effects can spread rapidly through social communication. This has been recently documented with the potential side-effects from the COVID-19 vaccines. We tested if pre-vaccination social communications about side-effects from personal acquaintances, news reports, and social media predict post-vaccination side-effect experiences. Further, as previous research suggests that side-effects can be exacerbated by negative expectations, we assessed if personal expectations mediate the relationships between social communication and side-effect experience. METHOD: In a prospective longitudinal survey (N = 551), COVID-19 vaccine side-effect information from three sources-social media posts, news reports, and first-hand accounts from personal acquaintances-as well as side-effect expectations, were self-reported pre-vaccination. Vaccination side-effect experience was assessed post-vaccination. RESULTS: In multivariate regression analyses, the number of pre-vaccination social media post views (ß = 0.17) and impressions of severity conveyed from personal acquaintances (ß = 0.42) significantly predicted an increase in pre-vaccination side-effect expectations, and the same variables (ßs = 0.11, 0.14, respectively) predicted post-vaccination side-effect experiences. Moreover, pre-vaccination side-effect expectations mediated the relationship between both sources of social communication and experienced side-effects from a COVID-19 vaccination. CONCLUSIONS: This study identifies links between personal acquaintance and social media communications and vaccine side-effect experiences and provides evidence that pre-vaccination expectations account for these relationships. The results suggest that modifying side-effect expectations through these channels may change the side-effects following a COVID-19 vaccination as well as other publicly discussed vaccinations and medications.

Blinding and sham control methods in trials of physical, psychological, and self-management interventions for pain (article II): a meta-analysis relating methods to trial results.

ABSTRACT: Sham interventions in randomized clinical trials (RCTs) of physical, psychological, and self-management (PPS) therapies for pain are highly variable in design and believed to contribute to poor internal validity. However, it has not been formally tested whether the extent to which sham controls resemble the treatment under investigation consistently affects trial outcomes, such as effect sizes, differential attrition, participant expectancy, and blinding effectiveness. Placebo- or sham-controlled RCTs of PPS interventions of clinical pain populations were searched in 12 databases. The similarity of control interventions to the experimental treatment was rated across 25 features. Meta-regression analyses assessed putative links between employed control interventions, observed effect sizes in pain-related outcomes, attrition, and blinding success. The sample included 198 unique control interventions, dominated by manual therapy and chronic musculoskeletal pain research. Meta-analyses indicated small-to-moderate benefits of active treatments over control interventions, across subgroups of manual therapies, exercise, and rehabilitation, and psychological intervention trials. Multiple meta-regression modelling demonstrated that similarity between sham control and tested interventions predicted variability in pain-related outcomes, attrition, and blinding effectiveness. Influential variables were differences relating to the extent of intervention exposure, participant experience, and treatment environments. The results support the supposed link between blinding methods and effect sizes, based on a large and systematically sourced overview of methods. However, challenges to effective blinding are complex and often difficult to discern from trial reports. Nonetheless, these insights have the potential to change trial design, conduct, and reporting and will inform guideline development.

Blinding and sham control methods in trials of physical, psychological, and self-management interventions for pain (article I): a systematic review and description of methods.

ABSTRACT: Blinding is challenging in randomised controlled trials of physical, psychological, and self-management therapies for pain, mainly because of their complex and participatory nature. To develop standards for the design, implementation, and reporting of control interventions in efficacy and mechanistic trials, a systematic overview of currently used sham interventions and other blinding methods was required. Twelve databases were searched for placebo or sham-controlled randomised clinical trials of physical, psychological, and self-management treatments in a clinical pain population. Screening and data extraction were performed in duplicate, and trial features, description of control methods, and their similarity to the active intervention under investigation were extracted (protocol registration ID: CRD42020206590). The review included 198 unique control interventions, published between 2008 and December 2021. Most trials studied people with chronic pain, and more than half were manual therapy trials. The described control interventions ranged from clearly modelled based on the active treatment to largely dissimilar control interventions. Similarity between control and active interventions was more frequent for certain aspects (eg, duration and frequency of treatments) than others (eg, physical treatment procedures and patient sensory experiences). We also provide an overview of additional, potentially useful methods to enhance blinding, as well as the reporting of processes involved in developing control interventions. A comprehensive picture of prevalent blinding methods is provided, including a detailed assessment of the resemblance between active and control interventions. These findings can inform future developments of control interventions in efficacy and mechanistic trials and best-practice recommendations.

Is laparoscopic excision for superficial peritoneal endometriosis helpful or harmful? Protocol for a double-blinded, randomised, placebo-controlled, three-armed surgical trial.

INTRODUCTION: Placebo-controlled surgical designs are recommended to ascertain treatment effects for elective surgeries when there is genuine doubt about the effectiveness of the surgery. Some elective surgeries for pain have been unable to show an effect beyond sham surgery, suggesting contributions from contextual factors. However, the nature of contextual factors in elective surgery is largely unexplored. Further, methodological difficulties in placebo-controlled surgical trials impact the ability to estimate the effectiveness of a surgical procedure. These include an overall lack of testing the success of blinding, absence of comparison to a no-surgery control group and dearth of test for neuropathic pain.For women with peritoneal endometriosis, there is uncertainty regarding the pain-relieving effect of surgery. Surgery may put patients at risk of complications such as postsurgical neuropathic pain, without guarantees of sufficient pelvic pain relief. The planned placebo-controlled trial aims to examine the effect of surgery on pelvic pain, widespread pain and neuropathic pain symptoms in women with peritoneal endometriosis, and to test the contribution of contextual factors to pain relief. METHODS AND ANALYSIS: One hundred women with peritoneal endometriosis will be randomised to either diagnostic laparoscopy with excision of endometrial tissue (active surgery), purely diagnostic laparoscopy (sham surgery) or delayed surgery (no-surgery control group). Outcomes include pelvic pain relief, widespread pain, neuropathic pain symptoms and quality of life. Contextual factors are also assessed. Assessments will be obtained at baseline and 1, 3 and 6 months postrandomisation. Mixed linear models will be used to compare groups over time on all outcome variables. ETHICS AND DISSEMINATION: The trial is approved by the Regional Ethics Committee in the Central Denmark Region (1-10-72-152-20). The trial is funded by a PhD scholarship from Aarhus University, and supported by a grant from 'Helsefonden' (20-B-0448). Findings will be published in international peer-reviewed journals and disseminated at international conferences. TRIAL REGISTRATION NUMBER: NCT05162794.