The placebo effect: From concepts to genes

A narrative review of the placebo effect: historical roots, current applications, and emerging insights

PURPOSE

Placebo is a term to define physiologically inactive compounds used in treatment that causes physical and emotional changes. The placebo effect, driven by expectation and conditioning, plays a significant role in various conditions like pain, depression, and Parkinson's disease, while the nocebo effect can hinder treatment outcomes. Understanding mechanisms such as neuromodulation and genetics has gained importance in modern medicine. This review aims to explore the clinical relevance of placebo responses, particularly in neuropsychiatric disorders, and their potential in personalized medicine. By integrating placebo research into healthcare, it highlights opportunities to enhance treatment efficacy, improve patient well-being, and reduce reliance on pharmacological interventions.

METHODS

A comprehensive literature search was conducted in PubMed, Scopus, and Google Scholar databases. Recent studies were reviewed to evaluate placebo effects, and the variability of the placebo response in neuropsychiatric disorders was summarized.

RESULTS

Placebo effects significantly impact treatment outcomes across various conditions, including Parkinson's disease, depression, pain syndromes, and epilepsy. The mechanisms involve neurobiological and psychological factors, with evidence suggesting that placebo interventions can modulate neurotransmitter activity and improve patient well-being.

CONCLUSION

Integrating placebo research into clinical practice may enhance treatment outcomes, reduce drug dependency, and support personalized medicine by tailoring interventions to individual placebo responsiveness. Understanding placebo and nocebo mechanisms can optimize therapeutic strategies while minimizing unnecessary pharmacological treatments.

Neuropsychological mechanisms of observational learning in human placebo effects

Scientific evidence indicates that placebo effects are psychoneurobiological events involving the contribution of distinct central nervous systems and peripheral physiological mechanisms that influence pain perception and other symptoms. Placebo effects can occur without formal conditioning and direct prior experience because crucial information can be acquired through observational learning. Observation of benefits in another person results in placebo effects of a magnitude like those induced by directly experiencing an analgesic benefit. Understanding the psychological mechanisms of observationally induced placebo effects is a complex and multifaceted endeavor. While previous reviews have highlighted various frameworks and models to understand these phenomena, the underlying biological mechanisms have been overlooked. We summarize critically current understanding of its behavioral and neural mechanisms. Understanding the neural mechanisms of hypoalgesia driven by observation can serve as a foundation for future development of novel theoretical and methodological approaches and ultimately, applications.

A scoping review of placebo and nocebo responses and effects: insights for clinical trials and practice

Placebo and nocebo responses and effects influence treatment outcomes across a variety of conditions. The current scoping review aims to synthesise evidence from systematic reviews and meta-analyses in both clinical and healthy populations, elucidating key determinants of placebo and nocebo responses and effects, including individual, clinical, psychological and contextual factors. Among the 306 publications identified, 83% were meta-analyses and 17% systematic reviews, with a predominance of research in medical specialties (81.7%) such as psychiatry and neurology. Placebo responses were significantly more studied than nocebo responses. Individual determinants (e.g., age), clinical determinants (e.g., baseline symptom severity) and psychological determinants (e.g., expectations) were found to influence placebo and nocebo outcomes. Contextual determinants, including trial design and the method of treatment administration, also played critical roles. Several key underinvestigated areas in the current body of systematic reviews and meta-analyses were also identified. This scoping review highlights valuable insights into the determinants of placebo and nocebo responses and effects on a group level, potentially offering practical implications for optimising clinical trial designs and enhancing patient care strategies in clinical practice. However, to fully leverage these benefits, it is crucial to address the underexplored topics through more rigorous investigations using a person-centred perspective.

Effect of occlusal appliances on the sleep of individuals with bruxism: A systematic review and meta-analyses

OBJECTIVE

This systematic review determined whether occlusal appliance use influences the sleep of individuals with sleep bruxism.

MATERIAL AND METHODS

Six databases and the gray literature were searched to identify randomized and non-randomized clinical trials comparing slow wave sleep and sleep quality of sleep bruxers before and after occlusal appliance use. The Risk of Bias was assessed using Cochrane tools and Meta-analyses were performed to compare data. The Certainty of the evidence was evaluated by Grading of Recommendations Assessment, Development, and Evaluation approach.

RESULTS

Two randomized and eight non-randomized studies were included. Meta-analyses indicated that soft and hard appliances influenced the slow-wave sleep and sleep quality of sleep bruxers, as determined by polysomnography (Z = 5.58; p < .001), the Pittsburgh Sleep Quality Index (Z = 3.45; p < .001), and the Sleep Assessment Questionnaire (Z = 48.1; p < .001).

CONCLUSION

Occlusal appliance use significantly impacts slow-wave sleep and sleep quality in sleep bruxism individuals, regardless of appliance design or material.

Enhancing placebo analgesia: Unravelling the powerful interplay of ownership and verbal suggestion

BACKGROUND

Placebo analgesic research demonstrates pain reduction after using a placebo analgesic. Recent studies have documented that sometimes possessing a placebo analgesic induces placebo analgesia. These prior studies used a 'cream' as the stimulus and proposed that the effect is driven by an expectancy of obtaining benefits from the owned analgesic. This paper examines three pivotal components of placebo analgesia: placebo form, ownership and expectancy induced by verbal suggestion. We investigate analgesic expectancy between cream versus oil form of placebo stimulus and systematically isolate the effects of ownership, verbal suggestion and their interaction, comparing with the effect of use, to decipher the dynamics of placebo analgesia.

METHODS

Study 1 (N = 46) evaluated analgesic expectancy between cream and oil. Study 2 (N = 119) exposed participants to a placebo analgesic oil and randomized them into PU (possess and use), PA (possess and anticipate), P (possess-only) or A (anticipate-only) conditions. Pain outcomes were assessed using a cold pressor test. Comparing PA and P conditions assessed the verbal suggestion effect, comparing PA and A conditions evaluated the possession effect, while comparing PU and PA conditions shed light on the use effect.

RESULTS

In Study 1, participants showed comparable analgesic expectancy for cream and oil. In Study 2, both PA and PU groups performed equally well, reporting higher pain threshold, F(3, 115) = 5.14, p = 0.002,η p 2  = 0.12; and a greater probability of persistent hand submersion than P and A groups, X2(3) = 8.06, p = 0.045.

CONCLUSION

The findings highlight the significance of integrating possession with expectancy to induce placebo analgesia, which has clinical implications.

SIGNIFICANCE

This study delves into the intricate dynamics of placebo analgesia, shedding light on the significant influence of ownership and verbal suggestion. Through a meticulous exploration of the relationship between ownership and expectancy induced by verbal suggestion, we propose novel avenues for enhancing placebo responses. This research has implications for clinical practice and pain management strategies, potentially revolutionizing approaches to pain relief and therapeutic outcomes. Our findings contribute to a paradigm shift in understanding placebo analgesia, emphasizing the pivotal interaction between ownership and verbal suggestion.

Reverse-engineering placebo analgesia

Placebo analgesia is a widely observed clinical phenomenon. Establishing a robust mouse model of placebo analgesia is needed for careful dissection of the underpinning circuit mechanisms. However, previous studies failed to observe consistent placebo effects in rodent models of chronic pain. We wondered whether strong placebo analgesia can be reverse engineered using general-anesthesia-activated neurons in the central amygdala (CeAGA) that can potently suppress pain. Indeed, in both acute and chronic pain models, pairing a context with CeAGA-mediated pain relief produced robust context-dependent analgesia, exceeding that produced by morphine in the same paradigm. CeAGA neurons receive monosynaptic inputs from temporal lobe areas that could potentially relay contextual cues directly to CeAGA neurons. However, in vivo imaging showed that CeAGA neurons were not reactivated in the conditioned context, despite mice displaying a strong analgesic phenotype. This finding suggests that the placebo-context-induced pain relief engages circuits beyond CeAGA neurons and relies on plasticity in other analgesic and/or nociceptive circuits. Our results show that conditioning with the activation of a central pain-suppressing circuit is sufficient to engineer placebo analgesia and that purposefully linking a context with an active treatment could be a means to harness the power of placebo for pain relief.

The development of an implicit measure of treatment expectations

In three preregistered studies, we investigated whether implicit treatment expectations, using a relational implicit measure (the MT-PEP), vary between participants provided opposing information about novel medical treatments (Studies 1 and 2) or who responded based on normative beliefs toward common over-the-counter drugs (Study 3). The studies revealed large Cohen's d effect sizes of both novel and well-known treatment information within the implicit measure. The studies also provide evidence of convergent validity, with MT-PEP scores associated with explicit beliefs about medicine and over-the-counter drug familiarity. Implicit treatment expectations can be assessed and offer a novel tool for the intersection of social psychology and medicine.

Placebo treatment affects brain systems related to affective and cognitive processes, but not nociceptive pain

Drug treatments for pain often do not outperform placebo, and a better understanding of placebo mechanisms is needed to improve treatment development and clinical practice. In a large-scale fMRI study (N = 392) with pre-registered analyses, we tested whether placebo analgesic treatment modulates nociceptive processes, and whether its effects generalize from conditioned to unconditioned pain modalities. Placebo treatment caused robust analgesia in conditioned thermal pain that generalized to unconditioned mechanical pain. However, placebo did not decrease pain-related fMRI activity in brain measures linked to nociceptive pain, including the Neurologic Pain Signature (NPS) and spinothalamic pathway regions, with strong support for null effects in Bayes Factor analyses. In addition, surprisingly, placebo increased activity in some spinothalamic regions for unconditioned mechanical pain. In contrast, placebo reduced activity in a neuromarker associated with higher-level contributions to pain, the Stimulus Intensity Independent Pain Signature (SIIPS), and affected activity in brain regions related to motivation and value, in both pain modalities. Individual differences in behavioral analgesia were correlated with neural changes in both modalities. Our results indicate that cognitive and affective processes primarily drive placebo analgesia, and show the potential of neuromarkers for separating treatment influences on nociception from influences on evaluative processes.

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.

Choice over placebo administration enhances open-label placebo hypoalgesia

ABSTRACT

Many studies indicate that deceptively administered placebos can improve pain outcomes. However, the deception involved presents an ethical barrier to translation because it violates informed consent and patient autonomy. Open-label placebos (OLPs), inert treatments that are openly administered as placebos, have been proposed as an ethically acceptable alternative. Early studies have suggested that OLP can improve pain outcomes, but important questions remain as to how to maximise OLP hypoalgesia to improve treatment outcomes in pain patients. This study investigated whether providing choice over when to administer an OLP treatment has the capacity to enhance OLP hypoalgesia using an electrocutaneous pain paradigm. One hundred thirty-two healthy volunteers were randomised to 3 types of treatment: OLP with choice, OLP without choice, and no treatment (natural history). The OLP groups were further randomised such that half were tested with a consistent pain intensity and the other half were tested with variable pain intensity to mimic day-to-day variability in pain intensity in health settings. The results indicated that treatment provided with choice exhibited greater OLP hypoalgesia than that provided without choice and that greater expectancy mediated this effect. Of interest, there was no evidence for OLP hypoalgesia without choice relative to natural history. Furthermore, variability in pain intensity did not affect OLP hypoalgesia. The current findings present novel evidence that choice over treatment administration may be a cheap and effective strategy for boosting the efficacy of OLPs in the clinical care of pain.

Efficacy and safety of herbal medicine Gongjin-Dan and Ssanghwa-Tang in patients with chronic fatigue: A randomized, double-blind, placebo-controlled, clinical trial

Background

Gongjin-dan (GJD, also known as Gongchen-dan) and Ssanghwa-tang (SHT, also known as Shuanghe-tang or Souwa-to) are herbal medicines that are widely used in Korea for treating fatigue. However, few studies have evaluated the efficacy and safety of GJD and SHT in the treatment of chronic fatigue.

Methods

In this randomized, double-blind, placebo-controlled clinical trial, 90 individuals with persistent (≥6 months) chronic fatigue of unknown cause and a Fatigue Severity Scale (FSS) score of ≥4 were randomly assigned to GJD group, SHT group, and control group in a 1:1:1 ratio. Outcomes were the changes in the self-reported fatigue questionnaire scores, levels of fatigue-related biomarkers and safety assessment.

Results

Out of 103 patients recruited, 90 were included in the analysis. A significant improvement in the Social Functioning (SF) score of Short-Form 36 Health Survey (SF-36) at week 4 was observed in the GJD group; similarly, a significant improvement compared with that in the Control group was observed in the Role Emotional (RE) score of SF-36 at weeks 4 and 6 and the Physical Functioning (PF) score of SF-36 at week 6 in the SHT group. Laboratory tests revealed no abnormalities, and serious intervention-related adverse events were not reported.

Conclusions

It is suggested that SHT can effectively treat chronic mental and physical fatigue, whereas GJD can effectively treat chronic mental and social fatigue. Furthermore, this study presents evidence supporting the safety of the long-term use of GJD and SHT (up to 4 weeks).

Trial registration

This study was registered at Clinical Research Information Service (CRIS) of Korea with the registration number KCT0007515.

Examining the effects of binaural beat music on sleep quality, heart rate variability, and depression in older people with poor sleep quality in a long-term care institution: A randomized controlled trial

OBJECTIVE

This study aimed to examine the effects of binaural beat music (BBM) on sleep quality, heart rate variability, and depression in older people with poor sleep quality in a long-term care institution.

METHODS

A single-blind randomized controlled trial design was employed, and 64 older participants with poor sleep quality were recruited from a long-term care institution in Taiwan. Participants were randomized into the BBM group or control group and received 14 days of intervention. During the intervention period, participants in the experimental group listened to 20 min of Taiwanese Hokkien oldies embedded with BBM once in the morning and afternoon three times a week. Participants in the control group only listened to Taiwanese Hokkien oldies. Questionnaires and heart rate variability analysis were used to assess participants' sleep quality, heart rate variability, and depressive symptoms.

RESULTS

Significant improvements were observed in sleep quality, along with an increase in heart rate variability means of heart rate and normal sinus beats, and a decrease in low-frequency normalized units and depression severity in the BBM group after the intervention. In the control group, effects on sleep quality were inconsistent, heart rate variability showed significant improvements in some autonomic nervous function regulation, and depression severity was significantly decreased. Furthermore, the BBM group showed a significant improvement in sleep quality and a significant reduction in sympathetic nervous activity compared with the control group.

CONCLUSION

This study demonstrates that 14 days of BBM intervention, a non-invasive intervention, could improve sleep quality and depression in older people with poor sleep quality in long-term care institutions. Geriatr Gerontol Int 2024; 24: 297-304.

Reverse engineering placebo analgesia

Placebo analgesia is a widely observed clinical phenomenon. Establishing a robust mouse model of placebo analgesia is needed for careful dissection of the underpinning circuit mechanisms. However, previous studies failed to observe consistent placebo effects in rodent models of chronic pain. We wondered whether strong placebo analgesia can be reverse engineered using general anesthesia-activated neurons in the central amygdala (CeA GA ) that can potently suppress pain. Indeed, in both acute and chronic pain models, pairing a context with CeA GA -mediated pain relief produced robust context-dependent analgesia, exceeding that induced by morphine in the same paradigm. We reasoned that if the analgesic effect was dependent on reactivation of CeA GA neurons by conditioned contextual cues, the analgesia would still be an active treatment, rather than a placebo effect. CeA GA neurons indeed receive monosynaptic inputs from temporal lobe areas that could potentially relay contextual cues directly to CeA GA . However, in vivo imaging showed that CeA GA neurons were not re-activated in the conditioned context, despite mice displaying a strong analgesic phenotype, supporting the notion that the cue-induced pain relief is true placebo analgesia. Our results show that conditioning with activation of a central pain-suppressing circuit is sufficient to engineer placebo analgesia, and that purposefully linking a context with an active treatment could be a means to harness the power of placebo for pain relief.

Short-term and long-term efficacy of accelerated transcranial magnetic stimulation for depression: a systematic review and meta-analysis

BACKGROUND

In recent years, accelerated transcranial magnetic stimulation (aTMS) has been developed, which has a shortened treatment period. The aim of this study was to evaluate the efficacy and long-term maintenance effects of aTMS in patients with major depressive disorder (MDD).

METHODS

We systematically searched online databases for aTMS studies in patients with MDD published before February 2023 and performed a meta-analysis on the extracted data.

RESULTS

Four randomized controlled trials (RCTs) and 10 before-and-after controlled studies were included. The findings showed that depression scores significantly decreased following the intervention (SMD = 1.80, 95% CI (1.31, 2.30), p < 0.00001). There was no significant difference in antidepressant effectiveness between aTMS and standard TMS (SMD = -0.67, 95% CI (-1.62, 0.27), p = 0.16). Depression scores at follow-up were lower than those directly after the intervention based on the depression rating scale (SMD = 0.22, 95% CI (0.06, 0.37), p = 0.006), suggesting a potential long-term maintenance effect of aTMS. Subgroup meta-analysis results indicated that different modes of aTMS may have diverse long-term effects. At the end of treatment with the accelerated repetitive transcranial magnetic stimulation (arTMS) mode, depressive symptoms may continue to improve (SMD = 0.29, 95% CI (0.10, 0.49), I2 = 22%, p = 0.003), while the accelerated intermittent theta burst stimulation (aiTBS) mode only maintains posttreatment effects (SMD = 0.01, 95% CI (-0.45, 0.47), I2 = 66%, p = 0.98).

CONCLUSIONS

Compared with standard TMS, aTMS can rapidly improve depressive symptoms, but there is no significant difference in efficacy. aTMS may also have long-term maintenance effects, but longer follow-up periods are needed to assess this possibility.

TRIAL REGISTRATION

This article is original and not under simultaneous consideration for publication. The study was registered on PROSPERO ( https://www.crd.york.ac.uk/prospero/ ) (number: CRD42023406590).

Influence of patients' preoperative expectations on postoperative outcomes after total knee or hip arthroplasty: a systematic review

Purpose

The association between preoperative expectations and treatment outcomes in total hip arthroplasty (THA) or total knee arthroplasty (TKA) is still unclear. Therefore the aim is to examine the association between preoperative outcome expectations, process expectations, and self-efficacy, and the postoperative outcomes overall outcome, pain, function, stiffness, satisfaction, and quality of life following THA/TKA.

Methods

A systematic review with narrative synthesis was conducted. PubMed, EMBASE, PsycINFO, CINAHL and Cochrane Library were searched from inception to October 17, 2022. Included were prospective longitudinal cohort studies published in English, German, or Dutch, with an adult population undergoing THA/TKA, and including at least one measure of preoperative expectations and the postoperative outcomes mentioned earlier. Two independent reviewers screened the retrieved articles for eligibility, a third solved disagreements. Risk of bias (RoB) was assessed using the QUIPS tool.

Results

Of the 50 included studies, 38 had high RoB and 12 moderate RoB. Unadjusted results suggest a positive association between preoperative outcome expectations and overall outcome in the medium and long term, and between self-efficacy and change in 'overall outcome' in the long term. Adjusted results suggest positive associations between outcome expectations and function and between self-efficacy and overall outcome in the medium term, and for outcome expectations with pain and change in pain, respectively, and self-efficacy and stiffness in the long term.

Conclusions

Preoperative expectations show a possible positive association with specific outcome measures, such as pain or function. For future research, it is advised to link matching specific expectations with specific outcomes.

Choice Enhances Placebo Hypoalgesia More in Weaker Placebo Contexts: A Partial Reinforcement Study

Providing individuals with choice over treatment has been found to enhance placebo hypoalgesia. However, this choice effect is not always present. The current study tested whether the strength of the placebo context influenced the effect of choice on placebo hypoalgesia. Using an established electrocutaneous pain paradigm, the choice effect was compared when placebo hypoalgesia was induced by Continuous Reinforcement (CRF) (strong placebo context) versus partial reinforcement (PRF) (weak placebo context). Healthy volunteers (N = 133) were randomized to receive either choice over treatment administration or no choice and then to placebo conditioning under either CRF (placebo always followed by surreptitious pain reduction during training) or PRF (placebo only followed by surreptitious pain reduction on half of the training trials). At the test, placebo hypoalgesia was greater and more resistant to extinction overall for those with choice. Importantly, however, the choice effect in enhancing the magnitude of placebo hypoalgesia was stronger after PRF than CRF. These results indicate that choice may have greater placebo-enhancing power in weaker placebo contexts. Therefore, choice may be a cheap and effective tool for improving clinical outcomes by facilitating placebo hypoalgesia when the existing treatment context is insufficient to produce placebo hypoalgesia itself. PERSPECTIVE: This study demonstrates that the enhancing effect of choice on placebo hypoalgesia is greater in a weaker placebo context. As such, offering choice could be an ethical way to effectively improve pain outcomes when placebo effects cannot be readily produced by the treatment context.

The Roles of Endogenous Opioids in Placebo and Nocebo Effects: From Pain to Performance to Prozac

Placebo and nocebo effects have been well documented for nearly two centuries. However, research has only relatively recently begun to explicate the neurobiological underpinnings of these phenomena. Similarly, research on the broader social implications of placebo/nocebo effects, especially within healthcare delivery settings, is in a nascent stage. Biological and psychosocial outcomes of placebo/nocebo effects are of equal relevance. A common pathway for such outcomes is the endogenous opioid system. This chapter describes the history of placebo/nocebo in medicine; delineates the current state of the literature related to placebo/nocebo in relation to pain modulation; summarizes research findings related to human performance in sports and exercise; discusses the implications of placebo/nocebo effects among diverse patient populations; and describes placebo/nocebo influences in research related to psychopharmacology, including the relevance of endogenous opioids to new lines of research on antidepressant pharmacotherapies.

Suggestion Timing Moderates the Effects of Prior Pain Experiences on Pain Perception

Two common elements in patient care are reoccurring painful events (eg, blood draws) and verbal suggestions from others for lessened pain. Research shows that verbal suggestions for lower pain can decrease subsequent pain perception from novel noxious stimuli, but it is less clear how these suggestions and prior painful experiences combine to influence the perception of a reoccurring painful event. The presented experiment tested the hypothesis that the order of these 2 factors influence pain perception for a reoccurring painful event. All participants (702 healthy college-student volunteers, 58% women, 85.5% White) experienced a novel painful event on one arm, then again on their other arm (now a familiar pain event). Participants who received the suggestion that they can tolerate more pain on the second arm relative to the first from the outset, before the initial pain event, perceived relatively less pain during the repeated event as compared to participants who received the same suggestion after the first painful event or no-suggestion (control). Given many pain events within medical contexts are, or become, familiar to patients, further researching the timing at which patients receive verbal suggestions for lower pain can inform practices to optimize the therapeutic, pain-reducing potential of such suggestions. PERSPECTIVE: Providing suggestions that a familiar pain event (ie, the second of 2) will be less painful than a prior event can reduce perceived pain for the familiar event depending on when it is presented. These findings can inform practices to optimize the therapeutic potential of verbal suggestions for reduced pain.

Familiarity From Facial Appearance Leads to Hypoalgesia

Social context has been shown to influence pain perception. This study aimed to broaden this literature by investigating whether relevant social stimuli, such as faces with different levels of intrinsic (based on physical resemblance to known individuals) and episodic (acquired through a previous experience) familiarity, may lead to hypoalgesia. We hypothesized that familiarity, whether intrinsic or acquired through experience, would increase pain threshold and decrease pain intensity. Sixty-seven participants underwent pain induction (the cold pressor test) viewing previously seen faces (Episodic Group) or new faces (Non-episodic Group) that differed in the level of intrinsic familiarity (high vs low). Pain threshold was measured in seconds, while pain intensity was measured on a rating scale of 0 to 10. The results did not show an effect of episodic familiarity. However, compared to low, high intrinsic familiar faces had an attenuating effect on pain intensity, even after controlling for pain expectation. These results suggest that physical features conveying a higher feeling of familiarity induce a top-down hypoalgesic modulation, in line with the idea that familiarity may signal safety and that the presence of familiar others reduce perceived threat-related distress. This study provides further evidence on the social modulation of pain and contributes to the literature on first impressions' influence on social behavior. PERSPECTIVE: Consistent with the idea that familiar others signal safety and reduce the sense of threat, facial features conveying familiarity induce a top-down hypoalgesic modulation. This knowledge may contribute to understanding differences in pain perception in experimental and clinical contexts.

Placebo and nocebo effects and mechanisms associated with pharmacological interventions: an umbrella review

OBJECTIVES

This review aimed to summarise the existing knowledge about placebo and nocebo effects associated with pharmacological interventions and their mechanisms.

DESIGN

Umbrella review, adopting the Assessment of Multiple Systematic Reviews 2 tool for critical appraisal.

DATA SOURCES

MEDLINE/PubMed, Scopus, Web of Science, PsycINFO, Cochrane Central Register of Controlled Trial were searched in September 2022, without any time restriction, for systematic reviews, narrative reviews, original articles. Results were summarised through narrative synthesis, tables, 95% CI.

OUTCOME MEASURES

Mechanisms underlying placebo/nocebo effects and/or their effect sizes.

RESULTS

The databases search identified 372 studies, for a total of 158 312 participants, comprising 41 systematic reviews, 312 narrative reviews and 19 original articles. Seventy-three per cent of the examined systematic reviews were of high quality.Our findings revealed that mechanisms underlying placebo and/or nocebo effects have been characterised, at least in part, for: pain, non-noxious somatic sensation, Parkinson's disease, migraine, sleep disorders, intellectual disability, depression, anxiety, dementia, addiction, gynaecological disorders, attention-deficit hyperactivity disorder, immune and endocrine systems, cardiovascular and respiratory systems, gastrointestinal disorders, skin diseases, influenza and related vaccines, oncology, obesity, physical and cognitive performance. Their magnitude ranged from 0.08 to 2.01 (95% CI 0.37 to 0.89) for placebo effects and from 0.32 to 0.90 (95% CI 0.24 to 1.00) for nocebo effects.

CONCLUSIONS

This study provides a valuable tool for clinicians and researchers, identifying both results ready for clinical practice and gaps to address in the near future.

FUNDING

Università Cattolica del Sacro Cuore, Milan, Italy with the 'Finanziamento Ponte 2022' grant.

PROSPERO REGISTRATION NUMBER

CRD42023392281.

To respond or not to respond: exploring empathy-related psychological and structural brain differences between placebo analgesia responders and non-responders

Introduction

Placebo responsiveness is highly variable across individuals. In the domain of pain, it may range from pronounced hypoalgesia to no response at all. Which factors predict such variation awaits clarification, as the available literature is characterized by mixed and inconclusive results. Particularly interesting in this case are social factors such as empathy or prosocial behavior, as prior work has stressed the connection between feeling pain yourself and empathizing with pain observed in others.

Methods

In a mixed confirmatory and exploratory approach, this study investigated potential psychological and structural brain differences between placebo responders and non-responders in the domain of pain. We aggregated data of four behavioral and neuroimaging studies that had been designed to investigate the effects of placebo analgesia on empathy.

Results

Analyses comparing groups of placebo responders and non-responders showed significant group differences in trait characteristics, with responders reporting increased helping behavior and lower psychopathic traits compared to non-responders. Uncorrected results further showed higher pain-related empathic concern in responders vs. non-responders. These results were accompaniedby tentative group differences in brain structure: placebo analgesia non-responders exhibited increased gray matter volume in left inferior temporal and parietal supramarginal cortical areas, and an increased cortical surface area in bilateral middle temporal cortex.

Discussion

Together, our findings suggest that modifiability of one's pain perception by means of placebo effects is linked to personality traits characterizing social emotions and behavior. They also hint that these psychological as well as brain structural characteristics might be beneficial for the identification of placebo responders. At the same time, they stress the importance of considering contextual factors such as the study setting or paradigm when investigating the association between individual characteristics and placebo responding.

Replication crisis and placebo studies: rebooting the bioethical debate

A growing body of cross-cultural survey research shows high percentages of clinicians report using placebos in clinical settings. One motivation for clinicians using placebos is to help patients by capitalising on the placebo effect's reported health benefits. This is not surprising, given that placebo studies are burgeoning, with increasing calls by researchers to ethically harness placebo effects among patients. These calls propose placebos/placebo effects offer clinically significant benefits to patients. In this paper, we argue many findings in this highly cited and 'hot' field have not been independently replicated. Evaluating the ethicality of placebo use in clinical practice involves first understanding whether placebos are efficacious clinically. Therefore, it is crucial to consider placebo research in the context of the replication crisis and what can be learnt to advance evidence-based knowledge of placebos/placebo effects and their clinical relevance (or lack thereof). In doing so, our goal in this paper is to motivate both increased awareness of replication issues and to help pave the way for advances in scientific research in the field of placebo studies to better inform ethical evidence-based practice. We argue that, only by developing a rigorous evidence base can we better understand how, if at all, placebos/placebo effects can be harnessed ethically in clinical settings.

Placebo effects in osteoarthritis: implications for treatment and drug development

Osteoarthritis (OA) is the most common form of arthritis worldwide, affecting ~500 million people, yet there are no effective treatments to halt its progression. Without any structure-modifying agents, management of OA focuses on ameliorating pain and improving function. Treatment approaches typically have modest efficacy, and many patients have contraindications to recommended pharmacological treatments. Drug development for OA is hindered by the gradual and progressive nature of the disease and the targeting of established disease in clinical trials. Additionally, new medications for OA cannot receive regulatory approval without demonstrating improvements in both structure (pathological features of OA) and symptoms (reduced pain and/or improved function). In clinical trials, people with OA show high 'placebo responses', which hamper the ability to identify new effective treatments. Placebo responses refer to the individual variability in response to placebos given in the context of clinical trials and other settings. Placebo effects refer specifically to short-lasting improvements in symptoms that occur because of physiological changes. To mitigate the effects of the placebo phenomenon, we must first understand what it is, how it manifests, how to identify placebo responders in OA trials and how these insights can be used to improve clinical trials in OA. Leveraging placebo responses and effects in clinical practice might provide additional avenues to augment symptom management of OA.

Placebo treatment affects brain systems related to affective and cognitive processes, but not nociceptive pain

Placebo analgesia is a replicable and well-studied phenomenon, yet it remains unclear to what degree it includes modulation of nociceptive processes. Some studies find effects consistent with nociceptive effects, but meta-analyses show that these effects are often small. We analyzed placebo analgesia in a large fMRI study (N = 392), including placebo effects on brain responses to noxious stimuli. Placebo treatment caused robust analgesia in both conditioned thermal and unconditioned mechanical pain. Placebo did not decrease fMRI activity in nociceptive pain regions, including the Neurologic Pain Signature (NPS) and pre-registered spinothalamic pathway regions, with strong support from Bayes Factor analyses. However, placebo treatment affected activity in pre-registered analyses of a second neuromarker, the Stimulus Intensity Independent Pain Signature (SIIPS), and several associated a priori brain regions related to motivation and value, in both thermal and mechanical pain. Individual differences in behavioral analgesia were correlated with neural changes in both thermal and mechanical pain. Our results indicate that processes related to affective and cognitive aspects of pain primarily drive placebo analgesia.

Longitudinal Meta-Analysis of Historical Parkinson's Disease Trials to Inform Future Trial Design

BACKGROUND

The outcome of clinical trials in neurodegeneration can be highly uncertain due to the presence of a strong placebo effect.

OBJECTIVES

To develop a longitudinal model that can enhance the success of future Parkinson's disease trials by quantifying trial-to-trial variations in placebo and active treatment response.

METHODS

A longitudinal model-based meta-analysis was conducted on the total score of Unified Parkinson's Disease Rating Scale (UPDRS) Parts 1, 2, and 3. The analysis included aggregate data from 66 arms (observational [4], placebo [28], or investigational-drug-treated [34]) from 4 observational studies and 17 interventional trials. Inter-study variabilities in key parameters were estimated. Residual variability was weighted by the size of study arms.

RESULTS

The baseline total UPDRS was estimated to average at 24.5 points. Disease score was estimated to worsen by 3.90 points/year for the duration of the treatments; whilst notably, arms with a lower baseline progressed faster. The model captured the transient nature of the placebo response and sustained symptomatic drug effect. Both placebo and drug effects peaked within 2 months; although, 1 year was needed to observe the full treatment difference. Across these studies, the progression rate varied by 59.4%, the half-life for offset of placebo response varied by 79.4%, and the amplitude for drug effect varied by 105.3%.

CONCLUSION

The longitudinal model-based meta-analysis describes UPDRS progression rate, captures the dynamics of the placebo response, quantifies the effect size of the available therapies, and sets the expectation of uncertainty for future trials. The findings provide informative priors to enhance the rigor and success of future trials of promising agents, including potential disease modifiers. © 2023 GSK. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Resilient Prescribing: An Approach to Psychotropic Use in Deployed Environments

Resilient prescribing is an approach to the use of psychotropics that considers the significance of the treatment beyond the direct effects of the medication. Within this strengths-based approach, those who are prescribed medications must retain a sense of self-efficacy, understand the importance of their own actions in their recovery, have reasonable expectations of what a medication can and cannot do, and avoid the adoption of a disempowering illness identity. These constitute the principles of resilient prescribing. In this manuscript, we explore these principles with consideration for how they may be applied in deployed settings where the ability of service members to recover from behavioral health concerns is mission critical. These principles offer a roadmap to prescribing that builds upon the service members' own strengths and has the potential to amplify the positive impacts of mental health treatment.

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.

The Emotion-Regulation Benefits of Implicit Reappraisal in Clinical Depression: Behavioral and Electrophysiological Evidence

Major depressive disorder (MDD) is characterized by emotion dysregulation. Whether implicit emotion regulation can compensate for this deficit remains unknown. In this study, we recruited 159 subjects who were healthy controls, had subclinical depression, or had MDD, and examined them under baseline, implicit, and explicit reappraisal conditions. Explicit reappraisal led to the most negative feelings and the largest parietal late positive potential (parietal LPP, an index of emotion intensity) in the MDD group compared to the other two groups; the group difference was absent under the other two conditions. MDD patients showed larger regulatory effects in the LPP during implicit than explicit reappraisal, whereas healthy controls showed a reversed pattern. Furthermore, the frontal P3, an index of voluntary cognitive control, showed larger amplitudes in explicit reappraisal compared to baseline in the healthy and subclinical groups, but not in the MDD group, while implicit reappraisal did not increase P3 across groups. These findings suggest that implicit reappraisal is beneficial for clinical depression.

Blinded Pain Cocktails: A Reliable and Safe Opioid Weaning Method

Weaning opioids in patients with noncancerous chronic pain often poses a challenge when psychosocial factors complicate the patient's chronic pain syndrome and opioid use. A blinded pain cocktail protocol used to wean opioid therapy has been described since the 1970s. At the Stanford Comprehensive Interdisciplinary Pain Program, a blinded pain cocktail remains a reliably effective medication-behavioral intervention. This review (1) outlines psychosocial factors that may complicate opioid weaning, (2) describes clinical goals and how to use blinded pain cocktails in opioid tapering, and (3) summarizes the mechanism of dose-extending placebos and ethical justification of its use in clinical practice.

Effect modifiers of virtual reality in pain management: a systematic review and meta-regression analysis

ABSTRACT

There is a rapidly growing body of evidence for the application of virtual reality (VR) in pain management, however, with varying effectiveness. Little is known about patient-related and VR-related factors affecting efficacy of VR. A systematic review and meta-analysis was performed including 122 randomised controlled trials (9138 patients), reporting on subjectively reported pain scores comparing an immersive VR intervention to a non-VR control group. Virtual reality significantly reduced pain in the pooled analysis (standardized mean difference = -0.65, 95% CI -0.76 to -0.54, P < 0.001). Subgroup analyses showed no significant differences between type of pain, ie, VR effects were similar in acute, chronic, and procedural pain conditions. Univariate and multivariate meta-regression analyses were performed to investigate the effect of intervention, patient, and pain characteristics on VR. Virtual reality effectively reduced pain, especially in patients reporting moderate to severe pain and in younger subjects. Studies comparing VR with a control group receiving no distraction methods were associated with higher effect sizes. The effect of VR was not related to a specific frequency or duration of use. Type of software and interaction level were related to VR effects in the univariable, but not in the multivariable, meta-regression analysis. Heterogeneity was considerable for all meta-analyses, and risk of bias was moderate to high in most included studies. Studies on mechanisms behind VR analgesia in younger patients and patients reporting moderate to severe pain are recommended to confirm our hypotheses while taking into account risk of bias and the comparator. Optimal application of VR using treatment modules for long-term pain conditions are an important issue for future research.

Systematic Review and Meta-analysis: Psychosocial Treatments for Disruptive Behavior Symptoms and Disorders in Adolescence

OBJECTIVE

Disruptive behavior disorders (DBDs) represent a common motive for referral among youths. This meta-analysis aimed at estimating the efficacy of psychosocial interventions for adolescents with DBDs.

METHOD

A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-compliant systematic review of MEDLINE/PubMED/PsycINFO/Cochrane Central Register of Controlled Trials was conducted. Eligible studies were randomized controlled trials (RCTs) administering psychosocial interventions to adolescents with DBD, published before April 5, 2020. From the initial set of 6,006 records, 17 RCTs involving 18 cohorts (16 publications) were subjected to a random-effect meta-analysis (involving sensitivity, subgroup, and meta-regression analyses). Primary and secondary outcomes were externalizing symptoms at RCT endpoint (ie, standardized mean difference [SMD]) and acceptability (drop-out odds ratio [OR]), respectively. Risk of bias was assessed using the Risk of Bias 2 tool.

RESULTS

A total of 17 RCTs, involving 1,954 adolescents, were included. The mean age was 14.09 (SD 1.33) years; 61% were male. The mean RCT duration was 12 weeks, with a mean follow-up of 8 (SD 3.98) months. Concern over risk of bias emerged in 12 studies, with high concern in 6. Psychosocial interventions had a large effect size at RCT endpoint (SMD = 0.98, 95% CI = -0.55 to -1.38, k = 18) and were acceptable (drop-out OR = 1.29, 95% CI = 0.62-2.70, k = 13). However, this beneficial effect did not persist at follow-up (SMD = -0.36, 95% CI = 0.06 to -0.78, k = 10). Family format was the most effective variable. No other clinically significant moderator was found.

CONCLUSION

Psychosocial interventions involving the families of DBD adolescents are effective and acceptable in the short term. Future studies should focus on strategies to achieve their long-term efficacy.

Probiotic supplements and stress-related occupational health outcomes: A scoping review

BACKGROUND

Prolonged and constant stress from work often leads to numerous adverse health effects. In recent years, interest in probiotics, living microorganisms that can benefit their host when consumed in adequate amounts, to aid health and well-being has increased. This scoping review is to systematically evaluate the current state of science on the effects of probiotic supplements on health, stress, and stress-related symptoms among working adults in occupational settings.

METHODS

We performed a systematic scoping review following the Arksey and O'Malley Framework. Studies that examined the effects of probiotics on workers' health and stress-related indicators/outcomes in occupational settings were included. A comprehensive search was performed from November 2021 to January 2022 using MEDLINE/PubMed, Cochrane Library, CINAHL, PsychInfo, Scopus, and Embase.

RESULTS

A total of 14 papers met the inclusion and exclusion criteria. Probiotics consisted primarily of Lactobacillus and/or Bifidobacterium strains in various forms and doses. Three out of eight studies reported statistical differences in inflammatory markers or stress hormone levels between probiotic and placebo groups. Three of six reported reduced respiratory tract infection incidents in the probiotic groups and three out of four studies reported no differences in anxiety and depression between groups. Lastly, three studies found that absenteeism and presentism were lower in probiotic groups compared with placebo groups.

CONCLUSION

The potential benefits of probiotics exist; however, the measurements of outcomes, the types of probiotics used, and the characteristics of the intervention varied across studies. Further research is needed focusing on probiotics' direct and indirect mechanisms of action on the stress response and the standardization of strains and dosing.

Choice and the nocebo effect: If a little is good, more is better?

OBJECTIVE

Lack of choice over treatment may increase the nocebo effect, whereby unpleasant side effects can be triggered by the treatment context, beyond any inherent physiological effects of the treatment itself. Excessive choice may also increase the nocebo effect. The current studies tested these possibilities.

METHOD

Participants took part in studies ostensibly investigating the influence of beta-blockers (Study 1, n = 71) and benzodiazepines (Study 2, n = 120) on anxiety. All treatments were placebos. In Study 1, participants were randomly allocated to three groups: no-treatment control, no-choice, and choice between two treatments. In Study 2, a ten-choice group was added. Participants were warned about possible treatment side effects. These warned symptoms were assessed, and scores summed. Nocebo effects were evidenced by significantly higher warned symptoms scores in any placebo-treated group compared to the control group.

RESULTS

In both studies, the no-choice groups experienced a nocebo effect (S1: p = .003, η_p²= 0.121; S2: p = .022, η_p²= 0.045). A significant nocebo effect was not present in groups who chose between two treatments (S1: p = .424, η_p²= 0.009; S2: p = .49, η_p²= 0.004). In Study 2, choosing between ten treatments resulted in a nocebo effect (p = .006, η_p²= 0.065).

CONCLUSION

Lack of choice resulted in the development of nocebo effects, while having a limited choice between two placebos did not generate significant nocebo effects. However, a larger choice between ten placebos generated a nocebo effect of similar magnitude to lack of choice. Facilitating (some) choice in medical care may reduce the development of nocebo effects, but more extensive choice options may not offer similar benefits.

The placebo response rate and nocebo events in obesity pharmacological trials. A systematic review and meta-analysis

BACKGROUND

There is a growing number of trials examining the effectiveness of pharmacotherapies for obesity, however, little is known about placebo and nocebo effect in these trials. Hence, we sought to examine the effect of placebo in obesity trials, to better understand the potential factors affecting clinical endpoints in them.

METHODS

Medline, Embase, and Cochrane CENTRAL were searched for articles examining weight-loss RCTs examining patients with overweight or obesity in placebo-controlled arms from inception till 25 June 2022. This paper was registered online with PROSPERO (CRD42022302482). A single arm meta-analysis of proportions was used to estimate the primary outcomes, ≥5%, ≥10%, and ≥15% total weight loss - and the adverse effects that patients experienced during the trial. A meta-analysis of means was used to estimate the pooled mean differences of the secondary outcomes including, body weight measurements, lipid levels, glycemic indices, and blood pressure over time.

FINDINGS

A total of 63 papers involving 20,454 patients and 69 trials were included. The proportion of patients that had ≥5%, ≥10%, and ≥15% weight loss was 20·4% (CI:16·1% to 25·0%), 8·3% (CI:6·1% to 10·9%), and 6·2% (CI:3·8% to 9·7%), respectively. Analysis by duration of trials showed stepwise increase in proportion of patients with ≥5% and ≥10% weight loss with increasing duration of study. Analysis of secondary outcomes found modest improvement in all analyses. The pooled average rate of overall AEs, serious AEs, and discontinuation was 73·7% (CI:68·0% to 79·0%), 3·4% (CI:2·4% to 4·5%), and 5·2% (CI:4·0% to 6·5%), respectively. In psychiatric complications, the pooled rates of anxiety and depression were 2·7% (CI:1·8% to 3·7%) and 2·5 (CI:1·7% to 3·3%).

INTERPRETATION

Our meta-analysis of placebo-treated participants in weight-loss RCTs indicate a significant placebo and nocebo effect. These findings are important to quantify their effect and may inform the design of future RCTs.

FUNDING

This research did not receive additional support from organizations beyond the authors' academic institutions.

The Impact of Probiotics and Prebiotics on Dry Eye Disease Signs and Symptoms

Dry eye is considered an inflammatory disease. Gut microbiota are important in the regulation of low-grade chronic inflammation, including in the eye. Probiotics and prebiotics are increasingly used to regulate chronic-disease-associated gut dysbiosis. Therefore, this double-masked, randomized controlled clinical trial aimed to explore the potential of oral probiotics and prebiotics in the management of dry eye disease. In total, 41 participants with dry eye received probiotic and prebiotic supplements (treatment group, n = 23) or respective placebos (control group, n = 18) for 4 months. Dry eye symptoms and signs were evaluated using the Ocular Surface Disease Index (OSDI), Dry Eye Questionnaire 5, osmolarity, non-invasive keratograph break-up time (NIKBUT), ocular surface staining, tear meniscus height (TMH), lipid layer thickness, and conjunctival redness. After 4 months, the average OSDI score of the treatment group was significantly better compared to that of the controls (16.8 ± 5.9 vs. 23.4 ± 7.4; p < 0.001). The NIKBUT and TMH did not change significantly with treatment (p = 0.31 and p = 0.84) but reduced significantly for controls on average by −5.5 ± 1.0 secs (p = 0.03) and 0.2 ± 0.1 mm (p = 0.02). These data suggest that probiotics and prebiotics might be effective in the management of dry eye disease.

Differences between experimental and placebo arms in manual therapy trials: a methodological review

BACKGROUND

To measure the specific effectiveness of a given treatment in a randomised controlled trial, the intervention and control groups have to be similar in all factors not distinctive to the experimental treatment. The similarity of these non-specific factors can be defined as an equality assumption. The purpose of this review was to evaluate the equality assumptions in manual therapy trials.

METHODS

Relevant studies were identified through the following databases: EMBASE, MEDLINE, SCOPUS, WEB OF SCIENCE, Scholar Google, clinicaltrial.gov, the Cochrane Library, chiloras/MANTIS, PubMed Europe, Allied and Complementary Medicine (AMED), Physiotherapy Evidence Database (PEDro) and Sciencedirect. Studies investigating the effect of any manual intervention compared to at least one type of manual control were included. Data extraction and qualitative assessment were carried out independently by four reviewers, and the summary of results was reported following the PRISMA statement.

RESULT

Out of 108,903 retrieved studies, 311, enrolling a total of 17,308 patients, were included and divided into eight manual therapy trials categories. Equality assumption elements were grouped in three macro areas: patient-related, context-related and practitioner-related items. Results showed good quality in the reporting of context-related equality assumption items, potentially because largely included in pre-existent guidelines. There was a general lack of attention to the patient- and practitioner-related equality assumption items.

CONCLUSION

Our results showed that the similarity between experimental and sham interventions is limited, affecting, therefore, the strength of the evidence. Based on the results, methodological aspects for planning future trials were discussed and recommendations to control for equality assumption were provided.

Use of Placebo and Nonoperative Control Groups in Surgical Trials: A Systematic Review and Meta-analysis

IMPORTANCE

Nonspecific effects, particularly placebo effects, are thought to contribute significantly to the observed effect in surgical trials.

OBJECTIVE

To estimate the proportion of the observed effect of surgical treatment that is due to nonspecific effects (including the placebo effect).

DATA SOURCES

Published Cochrane reviews and updated, extended search of MEDLINE, Embase, and CENTRAL until March 2019.

STUDY SELECTION

Published randomized placebo-controlled surgical trials and trials comparing the effect of the same surgical interventions with nonoperative controls (ie, no treatment, usual care, or exercise program).

DATA EXTRACTION AND SYNTHESIS

Pairs of authors independently screened the search results, assessed full texts to identify eligible studies and the risk of bias of included studies, and extracted data. The proportion of all nonspecific effects was calculated as the change in the placebo control divided by the change in the active surgery and pooled in a random-effect meta-analysis. To estimate the magnitude of the placebo effect, we pooled the difference in outcome between placebo and nonoperative controls and used metaregression to estimate the association between the type of control group and the treatment effect (difference between the groups), adjusting for risk of bias, sample size, and type of outcome.

MAIN OUTCOMES AND MEASURES

Between- and within-group effect sizes expressed as Hedges g.

RESULTS

In this review, 100 trials were included comprising data from 62 trials with placebo controls (3 also included nonoperative controls), and 38 trials with nonoperative controls (32 interventions; 10 699 participants). Risk of bias across trials was comparable except for performance and detection bias, which was high in trials with nonoperative controls. The mean nonspecific effects accounted for 67% (95% CI, 61% to 73%) of the observed change after surgery; however, this varied widely between different procedures. The estimated surgical placebo effect had a standardized mean difference (SMD) of 0.13 (95% CI, -0.26 to 0.51). Trials with placebo and nonoperative controls found comparable treatment effects (SMD, -0.09 [95% CI, -0.35 to 0.18]; 15 interventions; 73 between-group effects; adjusted analysis: SMD, -0.11 [95% CI, -0.37 to 0.15]).

CONCLUSIONS AND RELEVANCE

In this review, the change in health state after surgery was composed largely of nonspecific effects, but no evidence supported a large placebo effect. Placebo-controlled surgical trials may be redundant when trials with nonoperative controls consistently report no substantial association from surgery compared with nonoperative treatment.

Psycho-Neuro-Endocrine-Immunological Basis of the Placebo Effect: Potential Applications beyond Pain Therapy

The placebo effect can be defined as the improvement of symptoms in a patient after the administration of an innocuous substance in a context that induces expectations regarding its effects. During recent years, it has been discovered that the placebo response not only has neurobiological functions on analgesia, but that it is also capable of generating effects on the immune and endocrine systems. The possible integration of changes in different systems of the organism could favor the well-being of the individuals and go hand in hand with conventional treatment for multiple diseases. In this sense, classic conditioning and setting expectations stand out as psychological mechanisms implicated in the placebo effect. Recent advances in neuroimaging studies suggest a relationship between the placebo response and the opioid, cannabinoid, and monoaminergic systems. Likewise, a possible immune response conditioned by the placebo effect has been reported. There is evidence of immune suppression conditioned through the insular cortex and the amygdala, with noradrenalin as the responsible neurotransmitter. Finally, a conditioned response in the secretion of different hormones has been determined in different studies; however, the molecular mechanisms involved are not entirely known. Beyond studies about its mechanism of action, the placebo effect has proved to be useful in the clinical setting with promising results in the management of neurological, psychiatric, and immunologic disorders. However, more research is needed to better characterize its potential use. This review integrates current knowledge about the psycho-neuro-endocrine-immune basis of the placebo effect and its possible clinical applications.

A road map for happiness: The psychological factors related cell types in various parts of human body from single cell RNA-seq data analysis

Massive evidence from all sources including zoology, neurobiology and immunology has confirmed that psychological factors can raise remarkable physiological effects. Researchers have long been aware of the potential value of these effects and wanted to harness them in the development of new drugs and therapies, for which the mechanism study is a necessary prerequisite. However, most of these studies are restricted to neuroscience, or starts with blood sample and fall into the area of immunity. In this study, we choose to focus on the psychological factor of happiness, mining existing publicly available single cell RNA sequencing (scRNA-seq) data for the expression of happiness-related genes collected from various sources of literature in all types of cells in the samples, finding that the expression of these genes is not restricted within neuro-regulated cells or tissue-resident immune cells, on the opposite, cell types that are unique to tissue and organ without direct regulation from nervous system account for the majority to express the happiness-related genes. Our research is a preliminary exploration of where our body respond to our mind at cell level, and lays the foundation for more detailed mechanism research.

Can placebo and nocebo effects generalize within pain modalities and across somatosensory sensations?

Pain and other somatosensory sensations, such as itch, can be effectively decreased by placebo effects and increased by nocebo effects. There are indications that placebo effects on pain generalize to other sensations and that nocebo effects generalize within itch modalities. However, it has not yet been investigated whether learned effects can generalize within pain stimulus modalities or from pain to itch. Our aims were to test whether placebo and nocebo effects can generalize within pain modalities, ie, from heat pain to pressure pain, and across somatosensory sensations with psychophysiological similarities, ie, from heat pain to cowhage-evoked itch. For this purpose, 65 healthy participants were randomized to either a placebo or nocebo group. All participants first underwent a conditioning and verbal suggestion procedure with heat pain stimuli. Subsequently, responses to heat pain, pressure pain, and cowhage-evoked itch stimuli were tested. Results showed altered levels of heat and pressure pain with the conditioned cue in both placebo and nocebo groups in the expected directions, but no significant difference in itch in both groups. In conclusion, placebo and nocebo effects on pain may generalize within but not across stimulus modalities. This study provides a novel perspective on the role that response generalization plays in physical symptoms.

Music Intervention for Pain Control in the Pediatric Population: A Systematic Review and Meta-Analysis

Music intervention (MI) has been applied as an effective adjunctive treatment for pain control in various clinical settings. However, no meta-analysis has yet been published on the analgesic effects of MI in infants and children. We performed a systematic review of PubMed, EMBASE, Web of Science, and Cochrane Library databases to identify randomized controlled trials (RCTs) with the keywords "pain" AND "music therapy" from inception to January 2022. Primary outcomes were pain intensity and vital signs. Standardized mean difference (SMD) values and the corresponding 95% confidence intervals (CIs) were computed using a random effect model. Subgroup analyses with age groups, types of pain, and music styles were conducted. A total of 38 RCTs involving 5601 participants met the selection criteria. MI significantly decreased the pain levels (SMD = -0.57, p < 0.001), both in the newborn group (p = 0.007) and in the infant/children group (p < 0.001). MI significantly reduced heart rate (SMD = -0.50, p < 0.001) and respiratory rate (SMD = -0.60, p = 0.002) and increased peripheral capillary oxygen saturation (SMD = 0.44, p < 0.001). In subgroup analyses of types of pain, MI had significant effects on prick pain (p = 0.003), chronic and procedural pain (p < 0.001), and postoperative pain (p = 0.018). As for music styles, significant analgesic effects were observed for classical music (p < 0.001), kids' music (p < 0.001), and pop music (p = 0.001), but not for world music (p = 0.196), special composition (p = 0.092), and multiple music combinations (p = 0.420). In conclusion, our analysis provides supportive evidence about the efficacy of MI, especially classical, kids', and pop music, in controlling prick, procedural, and postoperative pain in the pediatric population.

Temporal expectancy induced by the mere possession of a placebo analgesic affects placebo analgesia: preliminary findings from a randomized controlled trial

Research on placebo analgesia usually shows that people experienced a reduction in pain after using a placebo analgesic. An emerging line of research argues that, under some circumstances, merely possessing (but not using) a placebo analgesic could induce placebo analgesia. The current study investigates how temporary expectation of pain reduction associated with different forms of possessing a placebo analgesic affects pain outcomes. Healthy participants (n = 90) were presented with a vial of olive oil (placebo), described as a blended essential oil that blocks pain sensations upon nasal inhalation, and were asked to anticipate the benefits of such analgesic oil to the self (such as anticipating the analgesic oil to reduce their pain). Participants were randomized into one of three different possession conditions: physical-possession condition (participants possessed a tangible placebo analgesic oil, inducing an expectation to acquire analgesic benefit early upon the experience of pain), psychological-possession condition (participants possessed a coupon, which can be redeemed for a placebo analgesic oil, inducing an expectation to acquire analgesic benefit later upon the experience of pain), or no-possession condition. Participants did a cold pressor test (CPT) to experience experimentally-induced pain on their non-dominant hand. Their objective physical pain responses (pain-threshold and pain-tolerance), and subjective psychological pain perception (pain intensity, severity, quality, and unpleasantness) were measured. Results revealed that participants in the physical-possession condition reported greater pain-threshold, F(2, 85) = 6.65, p = 0.002, and longer pain-tolerance, F(2, 85) = 7.19, p = 0.001 than participants in the psychological-possession and no-possession conditions. No significant group difference was found in subjective pain perception. The results of this study can advance knowledge about pain mechanisms and novel pain management.

How do placebo effects contribute to mindfulness-based analgesia? Probing acute pain effects and interactions using a randomized balanced placebo design

ABSTRACT

Recent sham-controlled studies suggest placebo effects contribute to acute pain relief following mindfulness interventions. However, the specific effects of mindfulness processes and their interaction with placebo effects remain unclear. This study aimed to characterize the role of mindfulness and placebo processes underlying mindfulness-based pain attenuation. Both treatment (focused-attention mindfulness vs sham) and instruction ("told mindfulness" vs "told sham") were manipulated in a balanced placebo design. Changes in acute heat pain were evaluated in 153 healthy adults randomized to receive 6 x 20 minutes of one of the four treatment by instruction interventions or no treatment. Participants receiving any intervention demonstrated improved pain outcomes (unpleasantness, intensity and tolerance) relative to no treatment. The instruction manipulation increased expectation for pain relief in those told mindfulness relative to told sham, but there were no main effects or interactions of treatment or instruction on pain outcomes. However, irrespective of actual intervention received, the belief of receiving mindfulness predicted increased pain threshold and tolerance, with expectancy fully mediating the effect on pain tolerance. These findings suggest a lack of specific effects of mindfulness and instruction on acute pain. Nonetheless, participants' expectancies and beliefs about the treatment they received did predict pain relief. Together with the overall improvement following any intervention, these findings suggest that expectancy and belief may play a stronger role in attenuating acute pain in novices following brief mindfulness interventions than the actual mindfulness-specific processes or instructions delivered.

Choice and the Placebo Effect: A Meta-analysis

Background

Choice has been proposed as a method of enhancing placebo effects. However, there have been no attempts to systematically evaluate the magnitude, reliability, and moderators of the influence of choice on the placebo effect.

Purpose

To estimate the effect size of choice on the placebo effect and identify any moderators of this effect.

Methods

Web of Science, PsycINFO, EMBASE, and PubMed were systematically searched from inception to May 2021 for studies comparing placebo treatment with any form of choice over its administration (e.g., type, timing) to placebo treatment without choice, on any health-related outcome. Random-effects meta-analysis was then used to estimate the effect size associated with the influence of choice on the placebo effect. Meta-regression was subsequently employed to determine the moderating effect of factors such as type of choice, frequency of choice, and size of the placebo effect without choice.

Results

Fifteen independent studies (N = 1,506) assessing a range of conditions, including pain, discomfort, sleep difficulty, and anxiety, met inclusion criteria. Meta-analysis revealed that choice did significantly enhance the placebo effect (Hedges’ g = 0.298). Size of the placebo effect without choice was the only reliable moderator of this effect, whereby a greater effect of choice was associated with smaller placebo effects without choice.

Conclusions

Treatment choice can effectively facilitate the placebo effect, but this effect appears more pronounced in contexts where the placebo effect without choice is weaker. Because most evidence to date is experimental, translational studies are needed to test whether providing choice in clinical scenarios where placebo effects are weaker may help boost the placebo effect and thereby improve patient outcomes.

Induction and generalization of nocebo effects on itch

Nocebo effects, that is, negative treatment outcomes due to negative expectancies, can increase itch. Moreover, indirect evidence has shown that nocebo hyperknesis can generalize to another itch modality. Knowledge on response generalization can help to prevent and decrease negative effects. The aims of this study were to investigate (1) the efficacy of inducing nocebo effects on cowhage‐evoked itch via verbal suggestions and (2) whether these effects can generalize to (2a) mechanically evoked touch and (2b) mechanically evoked itch. Forty‐four healthy participants watched a video suggesting that a nocebo solution increases cowhage‐evoked itch and that a control solution does not affect itch. Subsequently, cowhage, mechanical itch, and mechanical touch stimuli were applied. Nocebo effects were measured as the difference in both mean and peak of the outcomes itch and urge to scratch between nocebo and control trials. Main analyses revealed significant nocebo effects on mean and peak itch for all stimuli. For urge to scratch, a significant nocebo effect was only observed for mechanical touch (peak). As mechanical stimuli did not induce pure sensations as planned, posthoc sensitivity analyses were run for mechanical stimuli that individually induced either touch or itch at baseline. These analyses showed similar results for generalization to mechanical itch, but generalization to mechanical touch was non‐significant. This study showed that merely verbal suggestion can induce nocebo effects on cowhage‐evoked itch and that these effects can generalize to another itch modality. Future studies may examine how to prevent negative experiences from generalizing to subsequent encounters.

Do individual psychological characteristics predict induction and generalization of nocebo and placebo effects on pain and itch?

BACKGROUND

Nocebo and placebo effects, i.e., adverse or beneficial treatment effects, respectively, putatively due to expectancies can modulate pain and itch. These effects can generalize within the pain or itch modality. Predicting the induction and generalization of these effects can be helpful in clinical practice. This study aims to investigate whether psychological characteristics related to the fear-avoidance model predict the induction and generalization of nocebo and placebo effects on pain and itch in young healthy participants.

METHODS

Data from two previous experiments were analyzed. In Experiment 1, we induced nocebo and placebo effects on heat pain and tested generalization to pressure pain and to cowhage-evoked itch (n = 33 in a nocebo group, n = 32 in a placebo group). In Experiment 2, we induced nocebo effects on cowhage-evoked itch and tested generalization to mechanical itch and to mechanical touch (n = 44). Potential predictors were anxiety- and stress symptoms, attention to pain/itch, and pain/itch catastrophizing. Multiple regression analyses were performed.

RESULTS

For nocebo effects, none of the individual psychological characteristics significantly predicted induction of nocebo effects nor their generalization. For placebo effects, only less stress symptoms, lower attention to pain, and higher pain catastrophizing weakly predicted a stronger generalization of placebo effects from heat pain to pressure pain.

CONCLUSION

The tested psychological characteristics may not play an important role in the induction and generalization of nocebo and placebo effects in healthy individuals. However, firm conclusions cannot be drawn with the current sample. Future studies should validate findings in larger and more diverse samples.

Associations Between Interindividual Differences, Expectations and Placebo and Nocebo Effects in Itch

Introduction: Placebo and nocebo effects are positive and negative health outcomes that can be elicited by the psychosocial context. They can be mediated by expectations, and may emerge in somatic symptoms even when people are aware of these effects. Interindividual differences (e.g., in personality, affective states) could impact placebo and nocebo responding, but findings are inconsistent. Methods: The current work examined expectation as a mediator of the association between verbal placebo and nocebo suggestions (VSs) and histamine-induced itch across three experimental studies. Moreover, we examined whether interindividual differences (e.g., in optimism, neuroticism, behavioral activation system (BAS), body ignorance) modulated: (1) the direct association between VSs and itch (direct moderation), and (2) the indirect, expectation-mediated association between VSs and itch (moderated mediation). Positive VSs were compared to neutral instructions (Study 1; n = 92) or negative VSs (Studies 2+3; n = 203) in an open-label (i.e., explaining placebo and nocebo effects) or closed-label (concealed) context using PROCESS. First, mediation of VSs effects on itch by expectations was tested. Next, moderation by individual traits was explored using conditional process analyses. Results: The effects of VSs on itch were significantly mediated by expectation in Study 1 and in the open-label (but not closed-label) contexts of Studies 2 and 3. Ignorance of bodily signals marginally moderated the direct effects of VSs on itch when closed-label suggestions were given: at low levels of body ignorance, effects of positive and negative VSs were stronger. Moreover, moderated mediation was observed in the open-label groups of Studies 2 and 3: The expectation-mediated effects of VSs on itch were stronger when BAS drive was lower. Conclusion: Overall, the effects of VSs on itch were mediated by expectations in the open-label, but not the closed-label context. Moreover, the current work suggests that placebo and nocebo effects may be moderated by ignorance of bodily signals and the BAS. There was limited evidence that other interindividual differences modulated placebo and nocebo responding in itch.

The placebo and nocebo effects in functional urology

A placebo is an inert substance normally used in clinical trials for comparison with an active substance. However, a placebo has been shown to have an effect on its own; commonly known as the placebo effect. A placebo is an essential component in the design of conclusive clinical trials but has itself become the focus of intense research. The placebo effect is partly the result of positive expectations of the recipient on the state of health. Conversely, a nocebo effect is when negative expectations from a substance lead to poor treatment outcomes and/or adverse events. Randomized controlled trials in functional urology have demonstrated the importance of the placebo and nocebo effects across different diseases such as overactive bladder, urinary incontinence, lower urinary tract symptoms and interstitial cystitis/painful bladder syndrome, as well as male and female sexual dysfunction. Understanding the true nature of the placebo-nocebo complex and the scope of its effect in functional urology could help urologists to maximize the positive effects of this phenomenon while minimizing its potentially negative effects.

Spontaneously Generated Online Patient Experience of Modafinil: A Qualitative and NLP Analysis

Objective: To compare the findings from a qualitative and a natural language processing (NLP) based analysis of online patient experience posts on patient experience of the effectiveness and impact of the drug Modafinil.

Methods: Posts (n = 260) from 5 online social media platforms where posts were publicly available formed the dataset/corpus. Three platforms asked posters to give a numerical rating of Modafinil. Thematic analysis: data was coded and themes generated. Data were categorized into PreModafinil, Acquisition, Dosage, and PostModafinil and compared to identify each poster's own view of whether taking Modafinil was linked to an identifiable outcome. We classified this as positive, mixed, negative, or neutral and compared this with numerical ratings. NLP: Corpus text was speech tagged and keywords and key terms extracted. We identified the following entities: drug names, condition names, symptoms, actions, and side-effects. We searched for simple relationships, collocations, and co-occurrences of entities. To identify causal text, we split the corpus into PreModafinil and PostModafinil and used n-gram analysis. To evaluate sentiment, we calculated the polarity of each post between −1 (negative) and +1 (positive). NLP results were mapped to qualitative results.

Results: Posters had used Modafinil for 33 different primary conditions. Eight themes were identified: the reason for taking (condition or symptom), impact of symptoms, acquisition, dosage, side effects, other interventions tried or compared to, effectiveness of Modafinil, and quality of life outcomes. Posters reported perceived effectiveness as follows: 68% positive, 12% mixed, 18% negative. Our classification was consistent with poster ratings. Of the most frequent 100 keywords/keyterms identified by term extraction 88/100 keywords and 84/100 keyterms mapped directly to the eight themes. Seven keyterms indicated negation and temporal states. Sentiment was as follows 72% positive sentiment 4% neutral 24% negative. Matching of sentiment between the qualitative and NLP methods was accurate in 64.2% of posts. If we allow for one category difference matching was accurate in 85% of posts.

Conclusions: User generated patient experience is a rich resource for evaluating real world effectiveness, understanding patient perspectives, and identifying research gaps. Both methods successfully identified the entities and topics contained in the posts. In contrast to current evidence, posters with a wide range of other conditions found Modafinil effective. Perceived causality and effectiveness were identified by both methods demonstrating the potential to augment existing knowledge.