Role of placebo effects in pain and neuropsychiatric disorders

Effectiveness of Cold Therapy for Pain and Anxiety Associated with Chest Tube Removal: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

OBJECTIVES

To assess the effectiveness of cold therapy for pain and anxiety associated with chest tube removal.

DESIGN

A Systematic review and meta-analysis of randomized controlled trials.

DATA SOURCES

Articles were searched from Cochrane Library, PubMed, Embase, CINAHL, ProQuest, Airiti Library, China National Knowledge Infrastructure, and the National Digital Library of Theses and Dissertations in Taiwan.

REVIEW/ANALYSIS METHODS

Eight electronic databases were searched from inception to August 20, 2022. The Cochrane Risk of Bias 2.0 tool was used to assess the quality of the included studies. Using a random-effects model, we calculated Hedges' g and its associated confidence interval to evaluate the effects of cold therapy. Cochrane's Q test and an I2 test were used to detect heterogeneity, and moderator and meta-regression analyses were conducted to explore possible sources of heterogeneity. Publication bias was assessed using a funnel plot, Egger's test, and trim-and-fill analysis.

RESULTS

We examined 24 trials involving 1,821 patients. Cold therapy significantly reduced pain during and after chest tube removal as well as anxiety after chest tube removal (Hedges' g: -1.28, -1.27, and -1.80, respectively). Additionally, the effect size of cold therapy for reducing anxiety after chest tube removal was significantly and positively associated with that of cold therapy for reducing pain after chest tube removal.

CONCLUSIONS

Cold therapy can reduce pain and anxiety associated with chest tube removal.

Conditioning to Enhance the Effects of Repetitive Transcranial Magnetic Stimulation on Experimental Pain in Healthy Volunteers

OBJECTIVE

In this proof-of-concept study we sought to explore whether the combination of conditioning procedure based on a surreptitious reduction of a noxious stimulus (SRPS) could enhance rTMS hypoalgesic effects [i.e., increase heat pain threshold (HPT)] and augment intervention expectations in a healthy population.

METHODS

Forty-two healthy volunteers (19-35 years old) were enrolled in a randomized crossover-controlled study and were assigned to one of two groups: (1) SRPS and (2) No SRPS. Each participant received two consecutive sessions of active or sham rTMS over the M1 area of the right hand on two visits (1) active, (2) sham rTMS separated by at least one-week interval. HPT and the temperature needed to elicit moderate heat pain were measured before and after each rTMS intervention on the right forearm. In the SRPS group, conditioning consisted of deliberately decreasing thermode temperature by 3°C following intervention before reassessing HPT, while thermode temperature was held constant in the No SRPS group. Intervention expectations were measured before each rTMS session.

RESULTS

SRPS conditioning procedure did not enhance hypoalgesic effects of rTMS intervention, neither did it modify intervention expectations. Baseline increases in HPT were found on the subsequent intervention session, suggesting variability of this measure over time, habituation or a possible "novelty effect."

CONCLUSION

Using a SRPS procedure in healthy volunteers did not enhance rTMS modulating effects on experimental pain sensation (i.e., HPT). Future studies are therefore needed to come up with a conditioning procedure which allows significant enhancement of rTMS pain modulating effects in healthy volunteers.

Behavioral Conditioning, the Placebo Effect, and Emergency Department Pain Management

Animals and humans can be readily conditioned to associate a novel stimulus (often a unique taste) by pairing it with the effects of a drug or other agent. When later presented with the stimulus alone, their body's systems respond as if the drug or agent were given. The earliest clinical applications demonstrated both conditioned suppression and enhancement of immune processes. Unique benign stimuli, paired with chemotherapy, come to elicit T-cell suppression when administered alone. The beneficial immune responses to an antigen can be conditioned in the same manner. Further study of what came to be called "psychoneuroimmunology" led to the understanding that the familiar placebo effect, previously attributed to suggestion and expectation, is at least equally dependent on the same sorts of behavioral conditioning. The demonstrated ability to manipulate the immune system by a conditioned taste stimulus is, by definition, a placebo: a therapeutic effect caused by an inactive agent. The purpose of this analysis was to stimulate research in, and the application of, placebo-response conditioning to emergency medicine. Clinical and experimental studies confirm the usefulness of conditioned placebos in analgesia and in placebo-controlled dose reduction. Such conditioning paradigms demonstrate "one-trial learning," making them potentially useful in pain and addiction management within a single emergency department encounter.

Fecal Microbiota Transplantation in Neurological Disorders

Background: Several studies suggested an important role of the gut microbiota in the pathophysiology of neurological disorders, implying that alteration of the gut microbiota might serve as a treatment strategy. Fecal microbiota transplantation (FMT) is currently the most effective gut microbiota intervention and an accepted treatment for recurrent Clostridioides difficile infections. To evaluate indications of FMT for patients with neurological disorders, we summarized the available literature on FMT. In addition, we provide suggestions for future directions.

Methods: In July 2019, five main databases were searched for studies and case descriptions on FMT in neurological disorders in humans or animal models. In addition, the ClinicalTrials.gov website was consulted for registered planned and ongoing trials.

Results: Of 541 identified studies, 34 were included in the analysis. Clinical trials with FMT have been performed in patients with autism spectrum disorder and showed beneficial effects on neurological symptoms. For multiple sclerosis and Parkinson's disease, several animal studies suggested a positive effect of FMT, supported by some human case reports. For epilepsy, Tourette syndrome, and diabetic neuropathy some studies suggested a beneficial effect of FMT, but evidence was restricted to case reports and limited numbers of animal studies. For stroke, Alzheimer's disease and Guillain-Barré syndrome only studies with animal models were identified. These studies suggested a potential beneficial effect of healthy donor FMT. In contrast, one study with an animal model for stroke showed increased mortality after FMT. For Guillain-Barré only one study was identified. Whether positive findings from animal studies can be confirmed in the treatment of human diseases awaits to be seen. Several trials with FMT as treatment for the above mentioned neurological disorders are planned or ongoing, as well as for amyotrophic lateral sclerosis.

Conclusions: Preliminary literature suggests that FMT may be a promising treatment option for several neurological disorders. However, available evidence is still scanty and some contrasting results were observed. A limited number of studies in humans have been performed or are ongoing, while for some disorders only animal experiments have been conducted. Large double-blinded randomized controlled trials are needed to further elucidate the effect of FMT in neurological disorders.

Investigating Knowledge, Attitude, and Beliefs Regarding Placebo Interventions in Clinical Practice: A Comparative Study of Nursing and Medical University Students

BACKGROUND

Placebo interventions are commonly used in medical practice for alleviating symptoms of illnesses. Placebo is considered a pseudo-medication and its use is debatable ethically, professionally, and legally. Despite that there is also a lack of evidence on understanding of placebo interventions among health profession students. Further, no previous studies have been conducted to investigate whether future nurses and physicians differ in their knowledge, attitudes, and beliefs regarding placebo intervention.

MATERIALS AND METHODS

A comparative cross-sectional study was carried out for exploring knowledge, attitude, and beliefs about placebo interventions among a convenient sample of 187 medical and nursing students at King Saud bin Abdulaziz University for Health Sciences. Data were collected using a sociodemographic data sheet and a 32-item placebo knowledge, beliefs, and attitude scale, which was developed from the evidence-based literature. Validity and reliability were ensured through utilizing a panel of experts and internal consistency analysis.

RESULTS

Overall mean participants' knowledge score was 7.68±2.07 (out of 15). Nursing students showed significantly higher knowledge than medical students (P=0.028). More nursing than medical students believed in the effectiveness of placebo (P˂0.001). Medical students had a stronger belief that the placebo effect is mental, while nursing students reported that it is both mental and physiologic (P˂0.006). Concerning placebo attitude, medical students significantly pointed out that it should generally be prohibited and should not be permitted unless research supports its use (P˂0.001). Both groups agreed that impure placebo intervention involves deception.

CONCLUSION

Participants' overall placebo knowledge was low. Inconsistencies in attitude and beliefs were shown among students. Current study findings offered a unique opportunity to better study misunderstandings for placebo, which might open the gate for misuse and place patients at risk of deception. Additionally, study findings were imperative as a relevant evidence-based recommendation for nursing and medical educators could be achieved.

Open-label dose-extending placebos for opioid use disorder: a protocol for a randomised controlled clinical trial with methadone treatment

INTRODUCTION

More than 2 million individuals in the USA have an opioid use disorder (OUD). Methadone maintenance treatment is the gold standard of medication-based treatment for OUD, but high-dose methadone is associated with cardiotoxicity and respiratory complications, among other side effects. These adverse effects make enhancing the effectiveness of lower doses of methadone an attractive therapeutic goal. Long recognised for its capacity to enhance treatment outcomes for a wide range of neuropsychiatric disorders including pain, the placebo effect offers an as-yet untested avenue to such an enhancement. This approach is particularly compelling given that individuals with substance use disorder tend to have higher salience attribution and may thereby be more sensitive to placebo effects. Our study combines two promising clinical methodologies-conditioning/dose-extension and open-label placebo-to investigate whether placebo effects can increase the effective potency of methadone in treatment-seeking OUD patients.

METHODS AND ANALYSIS

A total of 120 newly enrolled treatment-seeking OUD patients will be randomly assigned to one of two different groups: either methadone plus daily placebo dose-extension (PDE; treatment group) or methadone/treatment as usual (control). Participants will meet with study team members five times over the course of 3 months of treatment with methadone (baseline, 2 weeks, and 1, 2 and 3 months postbaseline). Throughout this study time period, methadone dosages will be adjusted by an addiction clinician blind to patient assignment, per standard clinical methods. The primary outcome is methadone dose at 3 months. Secondary outcomes include self-report of drug use; 3-month urine toxicology screen results; and treatment retention. Exploratory outcomes include several environmental as well as personality factors associated with OUD and with propensity to demonstrate a placebo effect.

ETHICS AND DISSEMINATION

Human subjects oversight for this study is provided by the University of Maryland, Baltimore and University of Maryland, College Park Institutional Review Boards. Additionally, the study protocol is reviewed annually by an independent Data and Safety Monitoring Board. Study results will be disseminated via research conference presentations and peer-reviewed publications.

TRIAL REGISTRATION NUMBER

NCT02941809.

Placebo hypoalgesia: above and beyond expectancy and conditioning

Placebo hypoalgesia provides pain relief for individuals via the expectation of a beneficial or therapeutic outcome, while nocebo hyperalgesia results in increased pain in response to anxious anticipation of harmful outcomes. These forms of placebo pain modulation can be induced through repeated associations, verbal cues, and social interactions. Understanding these methods of pain modulation can provide greater insight into the psychosocial contexts of pain modulation, as well as develop novel approaches to pain management.

The Placebo Effect in Pain Therapies

Pharmacological strategies for pain management have primarily focused on dampening ascending neurotransmission and on opioid receptor-mediated therapies. Little is known about the contribution of endogenous descending modulatory systems to clinical pain outcomes and why some patients are mildly affected while others suffer debilitating pain-induced dysfunctions. Placebo effects that arise from patients' positive expectancies and the underlying endogenous modulatory mechanisms may in part account for the variability in pain experience and severity, adherence to treatment, distinct coping strategies, and chronicity. Expectancy-induced analgesia and placebo effects in general have emerged as useful models to assess individual endogenous pain modulatory systems. Different systems and mechanisms trigger placebo effects that highly impact pain processing, clinical outcomes, and sense of well-being. This review illustrates critical elements of placebo mechanisms that inform the methodology of clinical trials, the discovery of new therapeutic targets, and the advancement of personalized pain management.

Placebos Without Deception: Outcomes, Mechanisms, and Ethics

Scientific research indicates that open-label and dose-extending placebos (that patients know are placebos) can elicit behavioral, biological, and clinical outcome changes. In this chapter, we present the state-of-the-art evidence and ethical considerations about open-label and dose-extending placebos, discussing the perspective of giving placebos with a rational, as dose extension of active drugs, or expectancy boosters. Previous comprehensive reviews of placebo use have considered how to harness placebo effects in medicine and the need to focus on elements of the clinical encounter as well as patient-clinician relations. Here, we illustrate the similarities and differences between standard (deceptive) placebos, open-label placebos and dose-extending placebos. We conclude that placebos without deception would override ethical barriers to their clinical use. This paves the way to future large-scale, pragmatic randomized trials that investigate the potential of ethical open-label and dose-extending placebos to improve patients' outcomes, and reduce side effects.

Expectancy Modulation of Opioid Neurotransmission

Expectancies are powerful modulators of cognitive and emotional experiences, as well as the neurobiological responses linked to these processes. In medicine, placebo effects are a clear example of how expectancies activate opioid neurotransmission in a treatment context, leading to the experience of analgesia and the improvement of emotional states, among other symptoms. Molecular neuroimaging techniques using positron emission tomography (PET) and the selective μ-opioid receptor tracer [11C]carfentanil have significantly contributed to our understanding of the neurobiological systems involved in the formation of placebo effects. This line of research has described neural and neurotransmitter networks implicated in placebo effects and provided the technical tools to examine inter-individual differences in the function of placebo responsive mechanisms. As a consequence, the capacity to activate endogenous opioid networks during the administration of placebos has been linked to the concept of resiliency mechanisms, partially determined by genetic factors, and uncovered by the cognitive emotional integration of the expectations created by the therapeutic environment and its maintenance through learning mechanisms. This evidence has contributed to the understanding of the biological bases of the cognitive and psychological mechanisms implicated in the response to treatments, and opened up new opportunities for drug development and the enhancement of treatment responses. Further, delineation of these processes within and across diseases is critical to understand neural systems that could be enhanced to promote symptomatic improvement and modify disease progression.

Placebo Analgesia in Rodents: Current and Future Research

The investigation of placebo effects in animal pain models has received less attention than human research. This may be related to a number of difficulties, including the fact that animals lack the ability to use language and establish expectancies verbally, that animals cannot report and rate the extent to which they experience pain, and the inadequacy of current models of pain. Here, we describe the relatively small number of studies that have been published, communicating the opportunities and excitement of this research. We critically discuss pitfalls and limitations with the hope that this will advance future animal placebo-related research.

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.