Expectancy-Induced Placebo Analgesia in Children and the Role of Magical Thinking

The Importance of the Treatment Rationale for Pain in Animal-Assisted Interventions: A Randomized Controlled Trial in Healthy Participants

Animal-assisted interventions (AAIs) is a promising treatment approach for pain, but possible mechanisms still need to be elucidated. This study set out to investigate the analgesic effects of an animal provided with a treatment rationale in a randomized controlled trial employing a standardized experimental heat-pain paradigm. We randomly assigned 128 healthy participants to: dog treatment (DT), placebo treatment (PT), dog and placebo treatment (DPT), and no treatment (NT). Primary outcomes were heat-pain tolerance and the corresponding self-reported ratings of pain unpleasantness and intensity. Results revealed no differences in heat-pain tolerance between the conditions. However, participants in the DT condition experienced heat-pain as significantly less unpleasant at the limit of their tolerance compared to participants in the NT condition (estimate = -0.96, CI = -1.58 to 0.34, P = .010). Participants in the DT condition also showed lower ratings of pain intensity at the limit of their tolerance compared to participants in the NT condition (estimate = -0.44, CI = -0.89 to 0.02, P = .060). This study indicates that a dog has analgesic effects on pain perception when integrated into the treatment rationale. We assume that providing a treatment rationale regarding the animal is important in AAIs for pain. PERSPECTIVE: This study shows that the presence of an animal is not sufficient for animal-assisted interventions (AAIs) to have an analgesic effect on pain unless they are provided with a treatment rationale. This could imply that not only the animal but also contextual factors are important in AAIs. TRIAL REGISTRATION: Clinical Trials NCT04361968.

Expectations for Improvement: A Neglected but Potentially Important Covariate or Moderator for Chronic Pain Clinical Trials

Variability in pain-related outcomes can hamper assay sensitivity of chronic pain clinical trials. Expectations of outcome in such trials may account for some of this variability, and thereby impede development of novel pain treatments. Measurement of participants' expectations prior to initiating study treatment (active or placebo) is infrequent, variable, and often unvalidated. Efforts to optimize and standardize measurement, analysis, and management of expectations are needed. In this Focus Article, we provide an overview of research findings on the relationship between baseline expectations and pain-related outcomes in clinical trials of pharmacological and nonpharmacological pain treatments. We highlight the potential benefit of adjusting for participants' expectations in clinical trial analyses and draw on findings from patient interviews to discuss critical issues related to measurement of expectations. We conclude with suggestions regarding future studies focused on better understanding the utility of incorporating these measures into clinical trial analyses. PERSPECTIVE: This focus article provides an overview of the relationship between participants' baseline expectations and pain-related outcomes in the setting of clinical trials of chronic pain treatments. Systematic research focused on the measurement of expectations and the impact of adjusting for expectations in clinical trial analyses may improve assay sensitivity.

The Hand-Withdrawal-Method - An adapted and simplified method of limits for behavioral heat pain assessment

The method-of-limits (MLI) is an established psychophysical procedure, for example for determining thermal thresholds. The standard MLI relies on fixating the thermode at the stimulation site by means of a strap and requires the participant to terminate the increase in heat by pressing a button. This, however, raises concerns regarding safety and task complexity in specific populations, such as cognitively impaired individuals, people with high fear of pain or young children (< 6 years). In this study, we aimed at developing a simplified version of the commonly used MLI for testing heat pain threshold (HPT) and tolerance (HPTol), and at validating it as a first step in healthy adults. Heating is terminated by withdrawing the hand from the heat probe, thereby ensuring maximum control and safety. For validation, HPTs and HPTols were assessed with the novel "hand-withdrawal-method" (HWM) and compared to the standard MLI, using a within-subject design. Additionally, as one potential research area in which the HWM may be used, we explored expectancy-induced placebo hypoalgesic effects by comparing results of standard MLI with those of HWM. Our data confirm good concordance between the 2 methods. For none of the outcomes significant differences between the 2 methods were found. PERSPECTIVE: In the present study in healthy adults, an adapted simplified and safe method of limits was demonstrated to be equivalent to the standard method-of-limits. This novel behavioral "hand-withdrawal-method" seems promising for future investigations of pain sensitivity and placebo effects, especially for specific populations such as young children.

Deceptive and open-label placebo effects in experimentally induced guilt: a randomized controlled trial in healthy subjects

Placebos are known to yield significant effects in many conditions. We examined deceptive and open-label placebo effects on guilt, which is important for self-regulation and a symptom of mental disorders. Following an experimental induction of guilt, healthy subjects were randomized to deceptive placebo (DP; n = 35), open-label placebo (OLP; n = 35), or no treatment (NT; n = 39). The primary outcome was guilt responses assessed in area under the curve (AUC). Secondary outcomes were shame, guilt, and affect. We hypothesized that DP and OLP would reduce guilt compared to NT. Guilt responses were higher in the NT group than in the placebo groups (estimate = 2.03, 95% CI = 0.24-3.82, d = 0.53), whereas AUC guilt did not differ significantly between the placebo groups (estimate = -0.38, 95% CI = -2.52-1.76, d = -0.09). Placebos are efficacious in reducing acute guilt responses, regardless of the placebo administration (i.e., open vs. deceptive). Furthermore, we observed narrative-specific effects with significant changes of guilt but not shame, pride, or affect. These results indicate not only that guilt is amenable to placebos but also that placebos can be administered in an ethical and potentially emotion-specific manner.

Lack of Effects of the Presence of a Dog on Pain Perception in Healthy Participants-A Randomized Controlled Trial

Animal-assisted interventions (AAIs) have been shown to be effective in the treatment of pain. Studies suggest that relationships with animals can have comparable qualities to relationships with humans and that this enables animals to provide social support. Further, the presence of an animal can strengthen the therapeutic alliance between patients and treatment providers. This suggests that the analgesic effects of AAI might be mediated by social support from an animal or by strengthening the alliance between the patient and the treatment provider. To test these assumptions, we examined the effects of the presence of a dog on experimentally induced pain in a pain assessment and a pain therapy context. Hundred thirty-two healthy participants were randomly assigned to the conditions “pain,” “pain + dog,” “pain + placebo,” or “pain + placebo + dog.” We collected baseline and posttreatment measurements of heat-pain tolerance and the heat-pain threshold and of the corresponding subjective ratings of heat-pain intensity and unpleasantness as well as of participants' perceptions of the study investigator. The primary outcome was heat-pain tolerance. The presence of the dog did not influence the primary outcome (“pain” vs. “pain + dog”: difference = 0.04, CI = −0.66 to 0.74, p = 0.905; “pain + placebo” vs. “pain + placebo + dog”: difference = 0.43, CI = −0.02 to 0.88, p = 0.059). Participants did also not perceive the study investigator to be more trustworthy in the presence of the dog (“pain” vs. “pain + dog”: difference = 0.10, CI = −0.67 to 0.87, p = 0.796; “pain + placebo” vs. “pain + placebo + dog”: difference = 0.11, CI = −0.43 to 0.64, p = 0.695). The results indicate that the mere presence of a dog does not contribute to pain reduction and that the analgesic effects of AAI that previous studies have found is not replicated in our study as AAI did not increase perceived social support and had no effect on the alliance between the participant and the treatment provider. We assume that the animal most likely needs to be an integrated and plausible part of the treatment rationale so that participants are able to form a treatment-response expectation toward AAI.

Clinical Trial Registration: This study was preregistered as a clinical trial on www.clinicaltrials.gov (Identifier: NCT0389814).

Placebo and nocebo effects in youth: subjective thermal discomfort can be modulated by a conditioning paradigm utilizing mental states of low and high self-efficacy

Introduction:

Conditioning is a key mechanism of placebo and nocebo effects in adults, but little is known about these effects in youth. This study investigated whether personalized verbal cues evoking a sense of high or low self-efficacy can induce conditioned placebo and nocebo effects on subjective discomfort of noxious heat in youth.

Methods:

In a structured interview, 26 adolescents (13–18 years) described personal situations in which they experienced a sense of high, low or neutral self-efficacy. Participants were then asked to recall these memories during a conditioning paradigm, in which a high thermal stimulus applied to the forearm was repeatedly paired with a low self-efficacy cue and a low thermal stimulus with a high self-efficacy cue. In a testing phase, high, low and neutral self-efficacy cues were paired with the same moderate temperature. We hypothesized that conditioned high and low self-efficacy cues would induce conditioned placebo and nocebo responses to moderate temperatures.

Results:

Moderate temperatures were rated as more uncomfortable when paired with the conditioned low compared with the neutral self-efficacy cue (nocebo effect). While in the whole-group analysis, there was no significant difference between ratings of moderate thermal stimuli paired with high compared with neutral self-efficacy cues (placebo effect), a sub-group of participants with a greater range of emotional valence between high and neutral self-efficacy cues revealed a significant placebo effect. The strength of the nocebo effect was associated with higher anxiety and lower hope.

Conclusion:

Conditioned associations using internal self-efficacy states can change subjective discomfort of thermal sensations.

Placebo effect in children: the role of expectation and learning

Classical conditioning and expectations are well-known underlying mechanisms of placebo hypoalgesia. Only little is known about their differential effect in adults, however, and even less in children. Previous studies in children evoked placebo hypoalgesia either with expectations alone or in combination with classical conditioning and revealed conflicting results. Furthermore, these studies investigated children of different ages making it even more difficult to draw conclusions. This study tried to disentangle classical conditioning and expectations by investigating them separately. To examine age effects, n = 172 children (6-9, 10-13, and 14-17 years) as well as n = 32 adults (> = 18 years) were tested using a heat pain paradigm investigating the effectiveness of creams some of which were bogusly introduced as analgesic. In addition to subjective pain intensity ratings, peripheral physiological measures were recorded. Results showed a successful induction of placebo hypoalgesia by both mechanisms for pain ratings and heart rate acceleration. Placebo hypoalgesia was particularly pronounced in children younger than 14 years. Furthermore, placebo hypoalgesia was more marked in children whose mothers raised the expectations. It was also stronger in participants who noticed a strong pain reduction during learning trials. These results encourage the use of placebo effect in clinical practice, particularly for younger children. They underline the relevance of an initial pain reduction and encourage the inclusion of parents in treatment.

Effects of sex on placebo effects in chronic pain participants: a cross-sectional study

ABSTRACT

Sex-related differences can influence outcomes of randomized clinical trials and may jeopardize the effectiveness of pain management and other therapeutics. Thus, it is essential to understand the mechanistic and translational aspects of sex differences in placebo outcomes. Recently, studies in healthy participants have shed light on how sex-related placebo effects might influence outcomes, yet no research has been conducted in a patient population. Herein, we used a tripartite approach to evaluate the interaction of prior therapeutic experience (eg, conditioning), expectations, and placebo effects in 280 chronic (orofacial) pain patients (215 women). In this cross-sectional study, we assessed sex differences in placebo effects, conditioning as a proxy of prior therapeutic effects, and expectations evaluated before and after the exposure to positive outcomes, taking into account participant-experimenter sex concordance and hormonal levels (estradiol and progesterone assessed in premenopausal women). We used mediation analysis to determine how conditioning strength and expectations impacted sex differences in placebo outcomes. Independent of gonadal hormone levels, women showed stronger placebo effects than men. We also found significant statistical sex differences in the conditioning strength and reinforced expectations whereby reinforced expectations mediated the sex-related placebo effects. In addition, the participant-experimenter sex concordance influenced conditioning strength, reinforced expectations, and placebo effects in women but not in men. Our findings suggest that women experience larger conditioning effects, expectations, and placebo effects emphasizing the need to consider sex as a biological variable when placebo components of any outcomes are part of drug development trials and in pain management.

Talking to Children and Families about Chronic Pain: The Importance of Pain Education-An Introduction for Pediatricians and Other Health Care Providers

Chronic pain in children and adolescents is a common and debilitating health problem. This narrative review will give a brief overview on what pediatric chronic pain is and what treatment options there are for children and adolescents. The specific emphasis will be on pediatric chronic pain education and communication: this narrative review aims to show how important a good patient-health care provider relationship is-it builds the foundation for successful communication-and how this relationship can be established. In addition, we will present five steps that health care providers can perform to explain pediatric chronic pain to patients and their parents and what to keep in mind in their clinical routine. Our review is intended for pediatricians and other health care providers who treat pediatric patients with chronic pain but might feel uncertain on how to best communicate with them.

Pharmacokinetic and pharmacodynamic considerations of general anesthesia in pediatric subjects

Introduction: The target concentration strategy uses PKPD information for dose determination. Models have also quantified exposure-response relationships, improved understanding of developmental pharmacokinetics, rationalized dose prescription, provided insight into the importance of covariate information, explained drug interactions and driven decision-making and learning during drug development.Areas covered: The prime PKPD consideration is parameter estimation and quantification of variability. The main sources of variability in children are age (maturation) and weight (size). Model use is mostly confined to pharmacokinetics, partly because anesthesia effect models in the young are imprecise. Exploration of PK and PD covariates and their variability hold potential to better individualize treatment.Expert opinion: The ability to model drugs using computer-based technology is hindered because covariate data required to individualize treatment using these programs remain lacking. Target concentration intervention strategies remain incomplete because covariate information that might better predict individualization of dose is absent. Pharmacogenomics appear a valuable area for investigation for pharmacodynamics and pharmacodynamics. Effect measures in the very young are imprecise. Assessment of the analgesic component of anesthesia is crude. While neuromuscular monitoring is satisfactory, depth of anaesthesia EEG interpretation is inadequate. Closed loop anesthesia is possible with better understanding of EEG changes.

Effects of Expectancy on Cognitive Performance, Mood, and Psychophysiology in Healthy Adolescents and Their Parents in an Experimental Study

OBJECTIVE

Placebo effects on cognitive performance and mood and their underlying mechanisms have rarely been investigated in adolescents. Therefore, the following hypotheses were investigated with an experimental paradigm: (1) placebo effects could be larger in adolescents than in adults, (2) parents' expectations influence their adolescents' expectations and placebo effects, and (3) a decrease in stress levels could be an underlying mechanism of placebo effects.

METHODS

Twenty-six healthy adolescents (13.8 ± 1.6 years, 14 girls) each with a parent (45.5 ± 4.2 years, 17 mothers) took part in an experimental within-subjects study. On two occasions, a transdermal patch was applied to their hips and they received an envelope containing either the information that it is a Ginkgo patch to improve cognitive performance and mood, or it is an inactive placebo patch, in counterbalanced order. Cognitive performance and mood were assessed with a parametric Go/No-Go task (PGNG), a modification of California Verbal Learning Test, and Profile of Mood Scales (POMS). Subjects rated their expectations about Ginkgo's effects before patch application as well as their subjective assessment of its effects after the tests. An electrocardiogram and skin conductance levels (SCLs) were recorded and root mean square of successive differences (RMSSD), high-frequency power (HF), and the area under the curve of the SCL (AUC) were analyzed as psychophysiological stress markers.

RESULTS

Expectations did not differ between adolescents and parents and were correlated concerning reaction times only. Overall, expectations did not influence placebo effects. There was only one significant placebo effect on the percentage of correct inhibited trials in one level of the PGNG in adolescents, but not in parents. RMSSD and HF significantly increased, and AUC decreased from pre- to post-patch application in adolescents, but not in parents.

CONCLUSION

With this experimental paradigm, we could not induce relevant placebo effects in adolescents and parents. This could be due to aspects of the study design such as application form and substance, and that healthy subjects were employed. Nevertheless, we could show that adolescents are more sensitive to psychophysiological reactions related with interventions which could be part of the underlying mechanisms of placebo effects in adolescents.

Classical conditioning of antidepressant placebo effects in mice

INTRODUCTION

Placebo effects in human clinical trials for depression treatment are robust and often comparable to drug effects. Placebo effects are traditionally difficult to study in rodents due to the slow-onset action of classical antidepressant drugs. We hypothesized that the rapid antidepressant actions of ketamine would allow modeling antidepressant placebo effects in rodents.

METHODS

Male and female CD-1 mice received either ketamine or saline injections with concomitant exposure to specific environmental conditioning stimuli, for a total of three drug/conditioning sessions each 2 weeks apart. Two weeks later, during an evocation phase, mice were exposed to the drug-paired conditioning stimuli or no conditioned stimuli followed by testing for motor stimulatory actions and antidepressant-like effects using the forced swim test. Negative (no ketamine administration at any time) and positive (acute ketamine administration prior to evocation testing) control groups were included as comparators.

RESULTS

Both male and female mice exhibited increased locomotor activity following ketamine administration during the conditioning phase, which was not observed following exposure to the conditioning stimuli. Exposure to the conditioning stimuli previously paired with ketamine, similar to an acute ketamine administration, reduced immobility time in the forced swim test both 1 and 24 h after administration in male, but not female, mice.

CONCLUSIONS

These results represent the first evidence of antidepressant-like placebo-conditioned effects in an animal model. The developed approach can be used as a model to explore the neurobiological mechanisms of placebo effects, their possible sexually dimorphic effects, and relevance to mechanisms underlying antidepressant action.

Learning to fear pain after observing another's pain: An experimental study in schoolchildren

BACKGROUND

Children of individuals with chronic pain have an increased vulnerability to experience pain problems, possibly through observation of pain in their parents. As pain-related fear (PRF) is a critical factor in the development and maintenance of chronic pain, the current experimental study examined the acquisition of PRF through observational learning and subsequent extinction after first-hand experience of the feared stimulus.

METHODS

Healthy children (8-16 years) observed either their mother or a stranger performing two cold pressor tasks (CPT) filled with coloured water. In a differential conditioning procedure, one colour (CS+) was combined with genuine painful facial expressions and the other colour (CS-) with neutral facial expressions. Following this observation phase, children performed both CPTs (10°C) themselves.

RESULTS

Children expected the CS+ to be more painful than the CS- and they reported being more afraid and hesitant to immerse in the CS+ compared to the CS-. Moreover, this fear was reflected in children's level of arousal in anticipation of CPT performance. This learned association extinguished after performing both CPTs. Effects were not moderated by whether the child observed their mother or a stranger, by the child's pain catastrophizing, trait PRF or trait anxiety. Remarkably, learning effects increased when the child perceived a larger difference between the model's painful and neutral facial expressions.

CONCLUSIONS

This study provides evidence for observational learning of PRF and subsequent extinction in schoolchildren. This acquisition of PRF by observing parental pain may contribute to vulnerabilities in children of parents with chronic pain.

SIGNIFICANCE

Children may acquire pain-related fear by observing pain in others and this learned fear can diminish after first-hand experience. Remarkably, observational learning did not depend on the children's relationship with the model, but it did depend on the intensity of pain that is perceived. A better understanding of the impact of observing (parental) pain may help clarify the intergenerational transmission of risk for pain and inform the development of preventive programs.

Variation of spatiotemporal parameters in school children carrying different backpack loads: a cross sectional study

The purpose of this study was to analyze spatiotemporal parameters of gait in children using varyingly loaded Backpacks(BP). This cross-sectional study examined 231 schoolchildren (118 boys, 113 girls) aged six to 12 years, carrying a traditional BP to manipulate loading (Crossing Backpack Children Arpenaz 7 Litres, Junior Red Quechua). Load was added to the BPs in increments of 5%, 10%, 15% and 20% of the child's body weight. Spatio-temporal parameters were measured with the OptoGait system. Significant differences were observed in single support (p < 0.001), and double support (p < 0.001). No statistically significant differences were observed in step length (p = 0.959) between the five loading conditions. Similarly, no statistically significant differences were found in the contact phase (p = 0.208), although significant changes were seen between baseline, 15% of body weight (p < 0.005), and 20% of body weight (p < 0.005). The effect sizes from the ANOVA in the single support was low (0.015), and double support was moderate (0.02). Increased weight in BPs reduced both children's balance and single support, increased double support, but did not change step length. The children increase double support with heavier loads to help their balance. The spatio-temporal changes were most evident with BP loads between 15-20% of body weight. Affective responses, including the perception of heaviness or difficulty in carrying the schoolbags need to be included in further and prospective investigations.

Endogenous cortisol and conditioned placebo effects on pain - A randomized trial

Placebo effects can be induced by learning and conditioning processes, which in turn are influenced and modulated by glucocorticoids. Accordingly, previous research has shown that intervention-related associative learning can be modulated through exogenous as well as endogenous glucocorticoids. Thus, the aim of this study was to elucidate whether placebo effects induced by conditioning is modulated by daily fluctuations of endogenous cortisol levels in healthy male and female subjects. Overall 77 participants underwent a two-phased placebo conditioning paradigm for pain analgesia. Subjects were randomized in two groups, which underwent placebo preconditioning either in the morning (08:00-10:00, i.e. with high endogenous cortisol levels) or in the afternoon (16:00-18:00, i.e. with low endogenous cortisol levels). Placebo effects were assessed two days later at noontime (12:00-13:00), with possible differences between groups as an indicator of glucocorticoid modulation on the placebo learning. Results indicated a significant conditioned placebo-induced analgesia, resulting in a placebo effect of small to medium size. Cortisol levels on conditioning day significantly differed between groups and cortisol levels were similar during assessment of placebo effects. Groups did not differ in their mean reduction in pain sensation, thus the placebo effect was not affected by differences in cortisol levels during the conditioning of placebo effects. The present study does not indicate a moderation of placebo conditioning by endogenous glucocorticoid levels.

Does Sex/Gender Play a Role in Placebo and Nocebo Effects? Conflicting Evidence From Clinical Trials and Experimental Studies

Sex has been speculated to be a predictor of the placebo and nocebo effect for many years, but whether this holds true or not has rarely been investigated. We utilized a placebo literature database on various aspects of the genuine placebo/nocebo response. In 2015, we had extracted 75 systematic reviews, meta-analyses, and meta-regressions performed in major medical areas (neurology, psychiatry, internal medicine). These meta-analyses were screened for whether sex/gender differences had been noted to contribute to the placebo/nocebo effect: in only 3 such analyses female sex was associated with a higher placebo effect, indicating poor evidence for a contribution of sex to it in RCTs. This was updated with another set of meta-analyses for the current review, but did not change the overall conclusion. The same holds true for 18 meta-analyses investigating adverse event (nocebo) reporting in RCT in the placebo arm of trials. We also screened our database for papers referring to sex/gender and the placebo effect in experimental studies, and identified 28 papers reporting 29 experiments. Their results can be summarized as follows: (a) Despite higher sensitivity of pain in females, placebo analgesia is easier to elicit in males; (b) It appears that conditioning is effective specifically eliciting nocebo effects; (c) Conditioning works specifically well to elicit placebo and nocebo effects in females and with nausea; (d) Verbal suggestions are not sufficient to induce analgesia in women, but work in men. These results will be discussed with respect to the question why nausea and pain may be prone to be responsive to sex/gender differences, while other symptoms are less. Lastly, we will discuss the apparent discrepancy between RCT with low relevance of sex, and higher relevance of sex in specific experimental settings. We argue that the placebo response is predominantly the result of a conditioning (learning) response in females, while in males it predominantly may be generated via (verbal) manipulating of expectancies. In RCT therefore, the net outcome of the intervention may be the same despite different mechanisms generating the placebo effect between the sexes, while in experimental work when both pathways are separated and explicitly explored, such differences may surface.

Low-dose methoxyflurane analgesia in adolescent patients with moderate-to-severe trauma pain: a subgroup analysis of the STOP! study

Introduction

The undertreatment of acute pain presents a significant challenge in the Emergency Department. This post hoc subgroup analysis of a previously reported randomized controlled UK study reports the efficacy and safety of low-dose methoxyflurane analgesia in treating adolescent patients with moderate-to-severe trauma pain.

Patients and methods

Three hundred patients (96 in the adolescent subgroup) aged ≥12 years requiring analgesia for acute trauma pain (pain score of 4-7 on the Numerical Rating Scale) at triage were randomized 1:1 to methoxyflurane (up to 6 mL) or placebo (normal saline), both administered using a Penthrox^® inhaler. The patient could request rescue medication (paracetamol/opioids) at any time. The primary endpoint was the change from baseline in visual analog scale (VAS) pain intensity.

Results

Mean VAS pain score for the adolescent subgroup at baseline was ~ 61 mm. Adjusted mean change in VAS pain intensity from baseline to 5, 10, 15, and 20 minutes was -24.5, -28.1, -31.6, and -31.7 mm for methoxyflurane and -14.6, -18.8, -19.2, and -23.7 mm for placebo, with a statistically significant treatment effect in favor of methoxyflurane overall across all four time points (-9.9 mm; 95% CI: -17.4, -2.4 mm; P=0.0104). Median time to first pain relief was significantly shorter with methoxyflurane (1 minute) than placebo (3 minutes, P<0.0001). Pain relief was reported within 1-10 inhalations in 95.7% of methoxyflurane-treated patients and 64.6% of placebo-treated patients. Rescue medication was requested by two (4.3%) methoxyflurane-treated patients and three (6.3%) placebo-treated patients. Over 95% of patients, physicians, and nurses rated methoxyflurane treatment as "Excellent", "Very Good" or "Good" compared with between 64% and 68% for placebo. The incidence of adverse events was higher with methoxyflurane (51%) than placebo (42%), mostly comprising mild/transient dizziness and headache.

Conclusion

This subgroup analysis shows that low-dose inhaled methoxyflurane is a rapid-acting and effective analgesic in adolescent patients presenting with moderate-to-severe trauma pain.

Trial registration

Clinicaltrials.gov identifier: NCT01420159, EudraCT number: 2011-000338-12.

Open-label placebo response - Does optimism matter? A secondary-analysis of a randomized controlled trial

OBJECTIVE

Open-label placebos (OLPs) have been found to elicit significant and clinical meaningful effects, but in comparison to deceptive placebo administration there is a lack of research regarding possible predictors. This study sets out to examine the effects of optimism and other personality-related variables on OLP responses.

METHODS

We conducted a secondary-analysis of an OLP trial in healthy participants (N = 160), who were randomized to no treatment (NT), OLP without rationale (OPR^-), OLP with rationale (OPR⁺), and deceptive placebo (DP) in an experimental heat pain paradigm.

RESULTS

The association between objective posttreatment pain tolerance and optimism did not differ among groups. However, for subjective heat pain ratings at posttreatment, regression analyses showed a significant interaction between group and optimism scores in subjective intensity (F[3, 142] = 3.81, P = 0.012) and unpleasantness ratings (F[3, 142] = 2.95, P = 0.035), indicating that the association between optimism and subjective ratings differed among groups, in particular between OPR⁺ and NT (intensity: P = 0.012; unpleasantness: P = 0.037), and OPR⁺ and DP (intensity: P = 0.016). Thus, higher optimism scores were negatively associated with subjective ratings in the NT and DP groups but not in the OPR⁺ group. Additional exploratory analyses revealed no significant interactions between group and further personality-related variables on heat pain analgesia.

CONCLUSION

Taken together, OLPs are effective, the underlying personality-related variables seem, however, to differ significantly from the deceptive placebo response. Therefore, the concept of "placebo responders" might depend on the route of placebo administration.

Is the rationale more important than deception? A randomized controlled trial of open-label placebo analgesia

Research on open-label placebos questions whether deception is a necessary characteristic of placebo effects. Yet, comparisons between open-label and deceptive placebos (DPs) are lacking. We therefore assessed effects of open-label placebos and DPs in comparison with no treatment (NT) with a standardized experimental heat pain paradigm in a randomized controlled trial in healthy participants. Participants (N = 160) were randomly assigned to NT, open-label placebo without rationale (OPR-), open-label placebo with rationale (OPR), and DP. We conducted baseline and posttreatment measurements of heat pain threshold and tolerance. Apart from the NT, all groups received an application of a placebo cream. Primary outcomes were planned comparisons of heat pain tolerance and the corresponding intensity and unpleasantness ratings. Objective posttreatment pain tolerance did not differ among groups. However, for subjective heat pain ratings at the posttreatment tolerance level, groups with a rationale (OPR and DP) reported diminished heat pain intensity (t(146) = -2.15, P = 0.033, d = 0.43) and unpleasantness ratings (t(146) = -2.43, P = 0.016, d = 0.49) compared with the OPR-group. Interestingly, the OPR and the DP groups did not significantly differ in heat pain intensity (t(146) = -1.10, P = 0.272) or unpleasantness ratings (t(146) = -0.05, P = 0.961) at the posttreatment tolerance level. Our findings reveal that placebos with a plausible rationale are more effective than without a rationale. Even more, open-label placebos did not significantly differ in their effects from DPs. Therefore, we question the ubiquitously assumed necessity of concealment in placebo administration.

How to address the placebo response in the prescription SSRIs and SNRIs in children and adolescents

SSRIs and SNRIs are prescribed as first-line pharmacological treatment for common mental disorders in children and adolescents. Despite their efficacy, they have a high risk for adverse events and exhibit a substantial placebo response. This editorial provides some background on the current evidence on the topic and suggests to carefully weigh the benefits of SSRIs and SNRIs against their potential harms. Therefore, the authors present two different set of conclusions - one for clinical practice, and one for future research designs.

Anticipatory Effects on Perceived Pain: Associations With Development and Anxiety

OBJECTIVE

Naturalistic studies suggest that expectation of adverse experiences such as pain exerts particularly strong effects on anxious youth. In healthy adults, expectation influences the experience of pain. The current study uses experimental methods to compare the effects of expectation on pain among adults, healthy youth, and youth with an anxiety disorder.

METHODS

Twenty-three healthy adults, 20 healthy youth, and 20 youth with an anxiety disorder underwent procedures in which auditory cues were paired with noxious thermal stimulation. Through instructed conditioning, one cue predicted low-pain stimulation and the other predicted high-pain stimulation. At test, each cue was additionally followed by a single temperature calibrated to elicit medium pain ratings. We compared cue-based expectancy effects on pain across the three groups, based on cue effects on pain elicited on medium heat trials.

RESULTS

Across all groups, as expected, participants reported greater pain with increasing heat intensity (β = 2.29, t(41) = 29.94, p < .001). Across all groups, the critical medium temperature trials were rated as more painful in the high- relative to low-expectancy condition (β = 1.72, t(41) = 10.48, p < .001). However, no evidence of between-group differences or continuous associations with age or anxiety was observed.

CONCLUSIONS

All participants showed strong effects of expectancy on pain. No influences of development or anxiety arose. Complex factors may influence associations among anxiety, development, and pain reports in naturalistic studies. Such factors may be identified using experiments that employ more complex, yet controlled manipulations of expectancy or assess neural correlates of expectancy.

A systematic review of sex differences in the placebo and the nocebo effect

Objectives

The present review investigated whether there are systematic sex differences in the placebo and the nocebo effect.

Methods

A literature search was conducted in multiple electronic databases. Studies were included if the study compared a group or condition where a placebo was administered to a natural history group or similar cohort.

Results

Eighteen studies were identified – 12 on placebo effects and 6 on nocebo effects. Chi-square tests revealed that 1) males responded more strongly to placebo treatment, and females responded more strongly to nocebo treatment, and 2) males responded with larger placebo effects induced by verbal information, and females responded with larger nocebo effects induced by conditioning procedures.

Conclusion

This review indicates that there are sex differences in the placebo and nocebo effects, probably caused by sex differences in stress, anxiety, and the endogenous opioid system.

Parental Attitudes About Placebo Use in Children

OBJECTIVE

To assess parental attitudes regarding placebo use in pediatric randomized controlled trials and clinical care.

STUDY DESIGN

Parents with children under age 18 years living in the US completed and submitted an online survey between September and November 2014.

RESULTS

Among all 1300 participants, 1000 (76.9%; 538 mothers and 462 fathers) met the study inclusion criteria. The majority of surveyed parents considered the use of placebos acceptable in some pediatric care situations (86%) and some pediatric trials (91.5%), whereas only 5.7% of parents found the use of placebos in children always unacceptable. The clinical use of placebo was considered acceptable by a majority of parents for only 7 (mostly psychological) of the 17 conditions presented. Respondents' judgment about acceptability was influenced by the doctors' opinions about the therapeutic benefits of placebo treatment, the conditions for pediatric placebo use, transparency, safety, and purity of placebos.

CONCLUSION

Most surveyed parents accepted the idea of using placebos in pediatric trials and within the clinic for some conditions without the practice of deception and with the creation of guidelines for ethical and safe use. This study suggests a need to reconsider pediatric trial design and clinical therapy in the light of generally positive parental support of appropriate placebo use.

Childrens' left-turning preference is not modulated by magical ideation

The literature on human turning preferences is inconsistent. While the few studies with children below 14 years of age uniformly describe an overall left-turning (counterclockwise) tendency, a recent Internet study with more than 1500 adults found a right-sided (clockwise) bias. We set out to investigate spontaneous turning behaviour in children age 5-3 years and, based on neuropsychiatric work in adults, also explored a potential association with magical thinking. Findings indicated a clear left-turning preference, independent of a participant's sex and handedness. Whether a child responded a question about the existence of extrasensory communication in the affirmative or not was unrelated to direction and size of turning bias and lateral preference. Our results are consistent with a left-sided turning preference reported for children, but in opposition to the clockwise bias recently described in a large-scale study with adults. Whether they point to a maturational gradient in the preferred direction of spontaneous whole-body rotation or rather to a lack of comparability between measures used in observational versus Internet-based studies remains to be further investigated. Regarding a purported association between body turns and magical thinking, our study is preliminary, as only one single question was used to probe the latter.

[Communication with children: practical hints and tools for the anesthesiology routine]

BACKGROUND

Pediatric patients represent a special challenge both for the management of anesthesia and for communication, especially the anxious and screaming child. Children have specific features of fears, cognition, comprehension and skills depending on the stage of development. In addition, behavior and anxiety are strongly shaped by the parents who have to be incorporated.

AIM

This article presents the special features of children as well as practical strategies and aids for dealing with children in a perioperative setting.

MATERIAL AND METHODS

In children suggestibility and susceptibility to placebo and nocebo effects are increased. This makes them more sensitive to negative factors but can also be utilized for positive, constructive effects. Possibilities are presented which make use of the special characteristics of children. A number of examples from daily clinical routine are given.

RESULTS

A child's imagination, creativity and capability for dissociation in particular allow an effective application of indirect suggestion, metaphors, stories, changes in focus of attention, retreat to an inner or imagined safe place, reframing of disturbing noises and events, pacing and leading in small steps and an activation of inner resources. A hand puppet, a pet toy, a little magic trick, introducing a magic friend, acupoint for palpitations with self-affirmation, stick figure drawings, ceiling pictures or holding hands can be quite helpful. All medical devices and interventions can be explained in a way that children can understand and in positive statements without lying or neglecting the need for information.

CONCLUSION

Meeting at eye level, talking to the child instead of just about it, a language appropriate for children but not childish, comprehensible information and explanations, return of control and care more than pure technical distance, all play an important role. A serious look into such communication strategies can help the anesthetist to overcome uncertainties that a child can easily sense.

A Randomized Clinical Trial of Jet-Injected Lidocaine to Reduce Venipuncture Pain for Young Children

STUDY OBJECTIVE

The J-Tip (National Medical Products Inc, Irvine, CA) uses air instead of a needle to push lidocaine into the skin. To our knowledge, no studies have investigated its use for venipuncture in young children. We determine whether the J-Tip decreased venipuncture pain in young children compared with vapocoolant spray.

METHODS

Children aged 1 to 6 years were randomized into 3 groups: intervention (J-Tip), control (vapocoolant spray), and sham (vapocoolant spray and pop of an empty J-Tip). The procedure was videotaped and scored with the Face, Legs, Activity, Cry and Consolability (FLACC) tool at 3 points; baseline, before approach; device, at J-Tip deployment; and at venipuncture. The FLACC tool was scored 0 (none) to 10 (severe). Comparisons of pain scores over time were made with the generalized estimating equation. Venipuncture success and adverse effects were assessed and compared with χ(2).

RESULTS

Two hundred five children enrolled: intervention 96, control 53, and sham 56. There were no between-group differences in baseline characteristics. There was no mean change in pain scores from device to venipuncture in the intervention group (0.26; 95% confidence interval [CI] -0.31 to 0.82), but there was an increase in pain in the control (2.82; 95% CI 1.91 to 3.74) and sham (1.68; 95% CI 0.83 to 2.52) groups. This change was greater for the control and sham compared to the intervention group. There was no difference in venipuncture success between groups. No severe adverse events occurred. Minor adverse events were the same between groups.

CONCLUSION

Use of the J-Tip for children aged 1 to 6 years reduced venipuncture pain compared with vapocoolant spray or sham treatment.

Impact of short-term meditation and expectation on executive brain functions

Meditation improves executive functions such as attention and working memory processes. However, it remains unclear to what extent contextual effects contribute to these improvements, since the role of meditation-associated expectations has not been investigated so far. In a randomized, single-blind, deceptive, between-subject design we compared the impact of short-term meditation (MG) on executive functioning with an expectation (ECG) and a passive control group (CG) as well as the effect of positive and negative outcome expectations. Fifty-nine healthy meditation-naïve volunteers participated on three consecutive days (20 min/session). Five groups were examined: 2 MGs, 2 ECGs and 1 CG. While one MG and one ECG were given positive suggestions concerning the effect of meditation on attention, the other two groups were given negative suggestions. MGs practised a focused attention meditation technique; ECGs were told that they were practising meditation but were given instructions for a sham meditation. CG participants sat in silence with their eyes closed. Interference control (Stroop task), selective sustained attention (d2 task), figural and verbal fluency measures of executive functions were assessed. Results indicate that suggestions have a substantial impact on interference control and verbal fluency, with positive suggestions leading to an increase in performance, whereas negative suggestions impeded improvement. This proof of concept study demonstrates the importance of the implementation of a credible ECG to elucidate context effects in meditation processes. It also indicates that suggestions can modulate the small effect of meditation on verbal fluency.

Are Children the Better Placebo Analgesia Responders? An Experimental Approach

There is little information regarding changes in placebo responsiveness with age, although first predictors of placebo responders such as psychological and physiological processes have been identified. Reviews and meta-analyses indicate that placebo response rates in randomized controlled trials (RCTs) are higher in children and adolescents compared with adults. As these studies cannot control for age-dependent differences in the natural course of the disease, biases might contribute to different placebo rates in RCTs. To avoid these biases, this study investigated age-related differences in placebo responsiveness between children and adults in a well-established experimental model of placebo analgesia combining classic conditioning and expectation. Our data confirm placebo analgesic responses in children, which did not differ in magnitude from those of adults. The influence of previous experience on subsequent treatment outcome was stronger in children than in adults, indicating an increased relevance of learning processes for treatment outcomes in children. Further studies are needed to understand the influence of treatment-related learning processes in children and adolescents, which might critically determine treatment responsiveness during adulthood.

PERSPECTIVE

This study is the first to experimentally explore placebo analgesia and influences of previous experience on placebo responses in children compared with adults. We found comparable placebo responses in both groups and an increased relevance of learning processes for treatment outcomes in children.

Considerations when using pharmacokinetic/pharmacodynamic modeling to determine the effectiveness of simple analgesics in children

INTRODUCTION

Assessment of analgesic drugs includes comparative studies to other analgesics and local anesthesia blockade, number needed to treat estimates and opioid sparing descriptions. An additional methodology is to define the concentration-response relationship using pharmacokinetic/pharmacodynamic (PK/PD) modeling.

AREAS COVERED

A concentration-response relationship allows analgesic effect comparison between drugs for different acute pain types. Covariates such as size, age and organ function impact greatly on PK in children. The cumulative effect of confounding factors (e.g., pharmacogenetics, placebo and changes in baseline pain over time) complicates PD. Other factors (outcome measures, method of measurement, failure to account for study attrition) impact on outcome. Population PK/PD modeling approaches allow us to account for these various factors to some extent.

EXPERT OPINION

Nonlinear mixed effects models help interpret analgesic data and their use is increasing. The PK is relatively well understood. The next investigative step will involve investigation into covariate effects for PD. Mathematical functions for both placebo models and dropout models are well described and should be incorporated into analgesic effectiveness studies that investigate a range of doses. Improvements in pain assessment tools and a greater understanding of pharmacogenomics factors will help individualize analgesic therapy.

Pain and placebo in pediatrics: a comprehensive review of laboratory and clinical findings

Pain modulation by placebo mechanisms is one of the most robust and best-studied phenomena, yet almost all research investigating the mechanisms and implications of the placebo analgesia are based on adult research. After highlighting crucial aspects that need to be considered in studying pain modulation in children, this comprehensive review examines studies related to pain modulation with an emphasis on factors such as age, neural development and pain measures. We critically discuss psychological mechanisms underlying placebo effects, including (1) verbally induced expectations, (2) conditioning and learning mechanisms, and (3) child-parent-physician interactions. Taken together, research suggests that placebo mechanisms can affect therapeutic outcomes and potentially be exploited clinically to improve clinical outcomes in pediatric population. Recommendations for further investigating the mechanistic bases and harnessing placebo effects for supportive therapeutic applications are given.