Expectations about the effectiveness of pain- and itch-relieving medication administered via different routes

Nocebo expectations rather than placebo expectations affect topical pain relief: A randomized clinical trial

Patients' expectations and beliefs regarding the potential benefits and harms of medical interventions may induce placebo and nocebo effects, and affect the response to pain therapies. In a randomized clinical trial, we examined the effect of placebo and nocebo expectations on pain relief and adverse events (AEs) in association with a topical treatment among 65 cancer survivors experiencing chronic musculoskeletal pain. Participants received either a 1% camphor-based topical pain patch or a placebo treatment for 14 days. We measured pain severity with the worst pain item of the Brief Pain Inventory (BPI) at baseline and 14 days and treatment expectations at baseline with validated expectation questionnaires. We found that high vs. low nocebo expectations decreased pain severity improvements by 2.5 points (95% confidence interval [CI] -3.8 to -1.2; p<0.001) on a 0-10 numeric rating scale of the BPI and pain response rate by 42.7% (95% CI 0.2-0.6; p<0.001) at day 14, irrespective of placebo expectation status or treatment arms. Patients with high vs. low nocebo expectations in the true arm reported 22.4% more unwanted AEs. High nocebo expectations were associated with increased AEs by 39.5% (odds ratio: 12.0, 95% CI 1.2, 145.5; p=0.029) and decreased pain response in the true arm vs. placebo. Our study demonstrated that nocebo expectations, rather than placebo expectations, elevate the risk of AEs and compromise the effect of topical pain interventions. The findings raise the possibility that nocebo expectations may worsen somatic symptoms through heightening central pain amplification and should be further investigated.

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

BACKGROUND

The magnitude of placebo effects from physical and psychological 'sham' is unknown but could impact efficacy trials and treatment understanding. To quantify placebo effects, this systematic review of three-armed randomised controlled trials (RCTs) of physical and psychological interventions for pain compared outcomes in 'sham' control intervention and non-exposure arms.

METHODS

RCTs with treatment, 'sham' control intervention, and non-exposure groups were included, enrolling adults with any pain. A protocol was pre-registered (PROSPERO: CRD42023413324), and twelve databases searched from 2008 to July 2023. Trial methods and blinding were analysed descriptively and risk of bias assessed. Meta-analysis of pain measures at short-, medium- and long-term was performed with random-effects models of standardised mean differences (SMD).Studies were sub-grouped according to control intervention type.

RESULTS

Seventeen RCTs were included. The average short-term placebo effect was small (0.21 SMD, 0.1-0.33 95% CI, p = 0.0002, 1440 participants). It showed no heterogeneity (Tau2  = 0.1, I2  = 11%, p = 0.3), preventing meta-regression analyses of effect modifiers. However, sub-group analyses revealed larger placebo effects in manual control interventions compared to disabled devices and miscellaneous control interventions. Overall, placebo analgesia accounted for 39% of treatments' short-term effectiveness. No placebo effects were found at medium-term (7 RCTs, 381 participants) or long-term follow-up (3 RCTs, 173 participants).

CONCLUSIONS

The observed placebo analgesia has mechanistic and methodological implications, though its clinical importance may be limited. Control intervention design affects placebo effects, highlighting the importance of considering methodology in RCT interpretation. Review limitations include a small number of long-term studies and sample heterogeneity.

SIGNIFICANCE

This systematic review directly quantifies placebo effects from physical and psychological 'sham' control interventions and compares them to treatments' overall effectiveness. By doing so, the review enhances our understanding of placebo effects, their relative contribution in clinical trials, and their susceptibly to trial design. It poses further questions regarding the influence of blinding, participant expectations, and features of the therapeutic context. Overall, the insights provided by this review carry methodological significance and are important for the interpretation and synthesis of efficacy trials in this field.

The roles of expectation, comparator, administration route, and population in open-label placebo effects: a network meta-analysis

Three meta-analyses have demonstrated the clinical potential of open-label placebos (OLPs). However, there is a need to synthesize the existing evidence through more complex analyses that would make it possible to answer questions beyond mere efficacy. Such analyses would serve to improve the understanding of why and under what circumstances OLPs work (e.g., depending on induced expectations or across different control groups). To answer these questions, we conducted the first network meta-analyses in the field of OLPs. Our analyses revealed that OLPs could be beneficial in comparison to no treatment in nonclinical (12 trials; 1015 participants) and clinical populations (25 trials; 2006 participants). Positive treatment expectations were found to be important for OLPs to work. Also, OLP effects can vary depending on the comparator used. While the kind of administration route had no substantial impact on the OLP effects, effects were found to be larger in clinical populations than in nonclinical populations. These results suggest that the expectation, comparator, administration route, and population should be considered when designing and interpreting OLP studies.

Placebo effects on cutaneous pain and itch: a systematic review and meta-analysis of experimental results and methodology

ABSTRACT

Placebo effects, positive treatment outcomes that go beyond treatment processes, can alter sensations through learning mechanisms. Understanding how methodological factors contribute to the magnitude of placebo effects will help define the mechanisms by which these effects occur. We conducted a systematic review and meta-analysis of experimental placebo studies in cutaneous pain and itch in healthy samples, focused on how differences in methodology contribute to the resulting placebo effect magnitude. We conducted meta-analyses by learning mechanism and sensation, namely, for classical conditioning with verbal suggestion, verbal suggestion alone, and observational learning, separately for pain and itch. We conducted subgroup analyses and meta-regression on the type of sensory stimuli, placebo treatment, number of acquisition and evocation trials, differences in calibrated intensities for placebo and control stimuli during acquisition, age, and sex. We replicated findings showing that a combination of classical conditioning with verbal suggestion induced larger placebo effects on pain ( k = 68, g = 0 . 59) than verbal suggestion alone ( k = 39, g = 0.38) and found a smaller effect for itch with verbal suggestion alone ( k = 7, g = 0.14). Using sham electrodes as placebo treatments corresponded with larger placebo effects on pain than when topical gels were used. Other methodological and demographic factors did not significantly affect placebo magnitudes. Placebo effects on pain and itch reliably occur in experimental settings with varied methods, and conditioning with verbal suggestion produced the strongest effects. Although methods may shape the placebo effect to some extent, these effects appear robust overall, and their underlying learning mechanisms may be harnessed for applications outside the laboratory.

[Relevance of demographic and psychological factors in pruritus]

BACKGROUND

Pruritus is a frequent phenomenon in patients in dermatology. The severity of pruritus often cannot be explained by the severity of the underlying disease or chronification processes alone. Especially then, demographic and psychological variables should also be considered as moderators of the intensity of pruritus.

PURPOSE

Are there associations between sex, age, emotional and cognitive factors and pruritus intensity in patients with chronic pruritus (CP) and skin-healthy control subjects?

MATERIAL AND METHODS

Recently published studies on the abovenamed moderators of pruritus were searched for in PubMed, collated and the results are summarized.

RESULTS

It was found that women reported a higher intensity of pruritus than men. In addition, negative emotions such as fear, disgust, and anger are positively associated with pruritus in patients with CP. There are also associations between cognitive factors, such as attention, catastrophizing, and pruritus.

CONCLUSION

The associations between both demographic and psychological factors and pruritus should be considered in the diagnostics and treatment of pruritus. A psychological intervention as a complementary treatment should be considered whenever patients report associations between psychological experiences and pruritus and/or automatic or extensive scratching.

Atypical presentation of complex regional pain syndrome: neuropathic itching - A case report

Background

In some patients with neuropathic pain (NP), such as complex regional pain syndrome (CRPS), itching rather than pain is the main symptom making diagnosis and treatment difficult.

Case

We report a case of a 23-year-old male with a history of hypoxic brain damage who presented with pruritus of the left foot and ankle. His left foot was fractured, and he underwent surgery 6 months previously. After the operation and cast application, he developed uncontrolled pruritus, swelling, sweating, and flushing of the left foot skin with limping. On examination, he showed well-known features of CRPS without pain. He was diagnosed with an atypical CRPS with neuropathic itching (NI). With treatment modalities used for NP and CRPS, his pruritus subsided gradually, and the his ankle mobility improved.

Conclusions

Unexplained itching can be the main symptom in some CRPS patients. Treatment according to NP can improve symptoms of NI in CRPS patients.

Individual differences in mental imagery in different modalities and levels of intentionality

Mental imagery is a highly common component of everyday cognitive functioning. While substantial progress is being made in clarifying this fundamental human function, much is still unclear or unknown. A more comprehensive account of mental imagery aspects would be gained by examining individual differences in age, sex, and background experience in an activity and their association with imagery in different modalities and intentionality levels. The current online study combined multiple imagery self-report measures in a sample (n = 279) with a substantial age range (18-65 years), aiming to identify whether age, sex, or background experience in sports, music, or video games were associated with aspects of imagery in the visual, auditory, or motor stimulus modality and voluntary or involuntary intentionality level. The findings show weak positive associations between age and increased vividness of voluntary auditory imagery and decreased involuntary musical imagery frequency, weak associations between being female and more vivid visual imagery, and relations of greater music and video game experience with higher involuntary musical imagery frequency. Moreover, all imagery stimulus modalities were associated with each other, for both intentionality levels, except involuntary musical imagery frequency, which was only related to higher voluntary auditory imagery vividness. These results replicate previous research but also contribute new insights, showing that individual differences in age, sex, and background experience are associated with various aspects of imagery such as modality, intentionality, vividness, and frequency. The study's findings can inform the growing domain of applications of mental imagery to clinical and pedagogical settings.

Anxiety sensitivity and opioid misuse and dependence among trauma-exposed adults with chronic pain

It is unclear if anxiety sensitivity may serve as mechanism underlying the relation between posttraumatic stress symptom severity and opioid misuse and dependence among trauma-exposed persons with chronic pain. Therefore, the current study evaluated the explanatory role of anxiety sensitivity in the relations between posttraumatic stress symptom severity and opioid misuse and dependence. Participants included 294 trauma-exposed adults with chronic pain (71.4% female, M_age = 37.79 years, SD = 10.85, M_{pain rating} = 7.32/10) that reported current moderate to severe chronic pain and prescription opioid use. Participants were recruited via an online national survey in the United States of America. There were statistically significant indirect effects of posttraumatic stress symptom severity via anxiety sensitivity in relation to opioid misuse and dependence. The indirect effects of the reverse models for opioid misuse and dependence also were significant and suggest the potential for bi-directional relations; however, the magnitude of the effect was smaller in the tests of specificity than in the original models. The present findings provide initial empirical evidence that greater posttraumatic stress symptom severity is related to anxiety sensitivity, which in turn, is associated with increased opioid misuse and dependence among trauma-exposed individuals with chronic pain.

Is there a relationship between cannabis use problems, emotion dysregulation, and mental health problems among adults with chronic pain?

Cannabis is often used to manage pain among persons who suffer from chronic pain. Yet, despite much literature suggesting cannabis use problems are associated with mental health problems, little work has examined mechanisms of this relationship among a chronic pain population. Chronic pain is also associated with emotion dysregulation. Individuals with chronic pain who experience cannabis use problems may have less capacity to regulate negative emotions, which could relate to greater anxiety, depression, and suicidal ideation. Thus, the current study explored whether emotion dysregulation explained, in part, the relation between cannabis use problems and anxiety, depression, and suicidal ideation among adults with chronic pain. Participants were 431 opioid-using adults with current moderate to severe chronic pain, 176 were current cannabis users, of which 30.20% reported cannabis use problems. Results indicated a significant indirect relationship between cannabis use problems and anxiety [95% CI (.03, .05)], depression [95% CI (.03, .06)], and suicidal ideation [95% CI (.01, .01)] via emotion dysregulation. Tests of specificity suggested potential for a bi-directional effect for suicidal ideation (p < .001). Initial findings suggest that emotion dysregulation may be an important mechanism in the relationship between cannabis use problems and mental health among adults with chronic pain.

The Knowledge of Contextual Factors as Triggers of Placebo and Nocebo Effects in Patients With Musculoskeletal Pain: Findings From a National Survey

Backgrounds: Contextual factors (CFs) have been recently proposed as triggers of placebo and nocebo effects in musculoskeletal pain. CFs encompass the features of the clinician (e.g. uniform), patient (e.g. expectations), patient-clinician relationship (e.g. verbal communication), treatment (e.g. overt therapy), and healthcare setting (e.g. design). To date, the researchers' understanding of Italian patients' knowledge about the role of CFs in musculoskeletal pain is lacking. Objectives: The aim of this study was to investigate attitudes and beliefs of Italian patients with musculoskeletal pain about the use of CFs in clinical practice. Methods: A national sample of Italian patients with musculoskeletal pain was recruited from 12 outpatient private clinics in Italy. An invitation to participate in an online survey was sent to patients: a) exhibiting musculoskeletal pain; b) aged 18-75; c) with a valid e-mail account; and d) understanding Italian language. Survey Monkey software was used to deliver the survey. The questionnaire was self-reported and included 17 questions and 2 clinical vignettes on the patients' behavior, beliefs, and attitudes towards the adoption of CFs in clinical practice. Descriptive statistics and frequencies described the actual number of respondents to each question. Results: One thousand one hundred twelve patients participated in the survey. Five hundred seventy-four participants were female (52%). The average age of patients was 41.7 ± 15.2 years. Patients defined CFs as an intervention with an unspecific effect (64.3%), but they believed in their clinical effectiveness. They identified several therapeutic effects of CFs for different health problems. Their use was considered ethically acceptable when it exerts beneficial psychological effects (60.4%), but it was banned if considered deceptive (51.1%). During clinical practice, patients wanted to be informed about the use of CFs (46.0%) that are accepted as an addition to other interventions to optimize clinical responses (39.3%). Moreover, patients explained the power of CFs through body-mind connections (37.1%). Conclusion: Patients with musculoskeletal pain had positive attitudes towards the use and effectiveness of CFs when associated with evidence-based therapy. They mostly perceived the adoption of CFs in clinical practice as ethical.

An open-label randomized trial of intramuscular olanzapine versus oral clonidine for symptomatic treatment of opioid withdrawal in the emergency department

Background: Patients with opioid withdrawal often present to the Emergency Department (ED), but many EDs do not have the infrastructure in place to initiate treatment with opioid agonists (methadone or buprenorphine). Therefore, ED management often entails symptomatic control. The purpose of this study was to compare olanzapine to clonidine for the treatment of opioid withdrawal symptoms. Methods: This was a prospective, randomized clinical trial comparing 10 mg of IM olanzapine to 0.3 mg of oral clonidine for symptoms of opioid withdrawal. Adult (18 years and older) ED patients reporting a history of opioid use and symptoms consistent with withdrawal were eligible. Patients were excluded if they had already received treatment during the ED encounter, were pregnant, incarcerated, or unable to provide consent. Patients were randomized 1:1 to receive olanzapine or clonidine for their initial treatment. A baseline Clinical Opiate Withdrawal Scale (COWS) score was calculated. After 30 min, the patient could receive any additional treatment at the ED physician's discretion. The primary outcome was need for additional medication (rescue) within 1 h of study medication administration. Secondary outcomes included change in COWS score and adverse reactions. Results: We enrolled 63 patients (33 olanzapine, 30 clonidine). Demographic characteristics were similar for both groups (median age 45, range 21-67, 54% male) as well as baseline COWS score (median score 11). The median time since last opiate use was 48 h for both groups (range 4-116). Rescue was given within 1 h for olanzapine for 9 (27%) patients and for clonidine in 19 (63%) patients (difference 36%, 95% CI 13-59%). Decrease in COWS score at 1 h was 8.3 for olanzapine and 5.1 for clonidine (difference 3.2, 95% CI 0.3-6). Adverse events were uncommon: akathisia (1, olanzapine), hypotension (2, clonidine), respiratory depression (0). Conclusions: Treatment of opioid withdrawal symptoms with 10 mg of IM olanzapine results in a lower incidence of rescue medication administration and improved symptoms (COWS score) compared to 0.3 mg of oral clonidine.

Effects of Open- and Closed-Label Nocebo and Placebo Suggestions on Itch and Itch Expectations

Placebo and nocebo effects have been shown to influence subjective symptoms such as itch. These effects can be induced by influencing outcome expectations through, for example, combining the application of an inert substance (e.g., a cream) with verbal suggestions on the anticipated effects of this substance. Interestingly, placebo effects also occur when it is known that a treatment is inert (i.e., open-label placebo). However, no study to date has examined the efficacy of negative and positive verbal suggestions under similar open-label and closed-label (i.e., concealed placebo/nocebo) conditions in itch. A randomized controlled between-subjects study design was applied in which healthy volunteers (n = 92) were randomized to 1) an open-label positive verbal suggestion group, 2) a closed-label positive verbal suggestion group, 3) an open-label negative verbal suggestion group, or 4) a closed-label negative verbal suggestion group. Verbal suggestions were made regarding the topical application of an inert substance. Itch was evoked experimentally by histamine iontophoresis at baseline and again following suggestions. Itch expectations, self-reported itch during and following iontophoresis, and skin response parameters were measured. Positive suggestions were found to result in significantly lower expected itch than were negative suggestions in both open- and closed-label conditions. No effects of the suggestions on itch during iontophoresis were found, but significantly lower itch was reported in the 4 min following iontophoresis in the (combined open- and closed-label) positive compared with negative verbal suggestion groups. In addition, a smaller increase in skin temperature was found in the positive compared with negative suggestion groups. The findings illustrate a potential role of (open- and closed-label) placebo for optimizing expectations and treatment effects for itch in clinical practice. Clinical Trial Registration: Netherlands Trial Register, trial number: NTR6530.

Are Blue Pills Better Than Green? How Treatment Features Modulate Placebo Effects

Treatment-related expectations are important predictors for placebo effects in various medical conditions. They are formed by verbal and nonverbal cues during the administration of treatments, such as verbal suggestions, conscious and unconscious associations with previous treatments, characteristics of patients and health-care providers as well as perceptual characteristics of the treatment. This review provides an overview of studies that aimed to elucidate the impact of treatment characteristics on expectations and placebo effects. Results show that high price, brand label, the use of invasive placebos and high placebo dose increase the expectations toward the beneficial effect of a placebo treatment, which in turn boost the placebo effect. Neuroimaging studies provide first insights into the neurobiological mechanisms underlying these differential placebo effects.

[Placebo and nocebo effects on itch : Methodological and clinical implications]

Patients often experience positive (placebo) or negative (nocebo) treatment effects due to the positive or negative expectations they have about the treatment. Placebo and nocebo effects have only relatively recently received attention for itch. Experimental studies indicate that, in line with research in other areas, such as pain, learning via verbal suggestion and conditioning plays a key role in placebo and nocebo effects on itch. Results on contagious itch emphasize the role of observational learning and suggest that itch sensations might be particularly susceptible to suggestion and therefore placebo and nocebo effects. Substantial itch reductions in the placebo arms of clinical trials suggest that placebo effects are also important for clinical practice. In this article, an overview is given of how placebo and nocebo effects on itch can optimally be used in research and for the treatment of itch.