Observer influences on pain: an experimental series examining same-sex and opposite-sex friends, strangers, and romantic partners

Verbal Support From a Stranger Reduces the Development of Mechanical Hypersensitivity: Behavioral and Neurophysiological Evidence

Hand-holding reduces experimentally induced acute pain and buffers against the development of mechanical secondary hypersensitivity, an indirect proxy of central sensitization. Here, we tested if verbal support from a stranger, a common occurrence in clinical contexts, exerts the same effects. In this preregistered study, 44 healthy female participants were assigned to an alone or support group whereby a supportive female stranger encouraged them through the painful procedure leading to secondary mechanical hypersensitivity. Mechanical hypersensitivity was measured via self-reports and by the size of the anteroposterior and mediolateral spread of mechanical hypersensitivity. We investigated the moderating role of attachment style on self-reports and the effects of support on skin conductance level, salivary cortisol, and pinprick-evoked potentials. We also tested whether theta/beta ratio in the resting-state electroencephalogram predicted mechanical hypersensitivity. Self-reported ratings and the late part of the pinprick-evoked potentials were reduced in the support group, but the spread of mechanical hypersensitivity was not. Attachment anxiety and avoidance moderated the self-reported intensity such that individuals with higher attachment anxiety and avoidance scores reported lower intensity ratings in the support group. No significant effect of the verbal support was observed on skin conductance level and salivary cortisol. The theta/beta ratio did not predict the extent of hypersensitivity. Our data indicate that, in women, verbal support during intense pain leading to hypersensitivity is effective on some behavioral outcomes, but altogether the lack of group differences in cortisol, self-reported stress, and skin conductance does not provide strong support for the stress-buffering hypothesis. PERSPECTIVE: Verbal support by a stranger during a painful procedure leading to secondary mechanical hypersensitivity attenuated the development of some measures of mechanical hypersensitivity and associated neural responses in healthy female participants. No evidence was found for the role of stress. DATA AVAILABILITY: The authors will make all data available upon request.

Healthy women show more experimentally induced central sensitization compared with men

ABSTRACT

Women more often experience chronic pain conditions than men. Central sensitization (CS) is one key mechanism in chronic pain that can differ between the sexes. It is unknown whether CS processes are already more pronounced in healthy women than in men. In 66 subjects (33 women), a thermal CS induction protocol was applied to the dorsum of one foot and a sham protocol to the other. Spatial extent [cm 2 ] of secondary mechanical hyperalgesia (SMH) and dynamic mechanical allodynia were assessed as subjective CS proxy measures, relying on verbal feedback. Changes in nociceptive withdrawal reflex magnitude (NWR-M) and response rate (NWR-RR) recorded through surface electromyography at the biceps and rectus femoris muscles were used as objective CS proxies. The effect of the CS induction protocol on SMH was higher in women than in men (effect size 2.11 vs 1.68). Nociceptive withdrawal reflex magnitude results were statistically meaningful for women (effect size 0.31-0.36) but not for men (effect size 0.12-0.29). Differences between men and women were not meaningful. Nociceptive withdrawal reflex response rate at the rectus femoris increased in women after CS induction and was statistically different from NWR-RR in men (median differences of 13.7 and 8.4% for 120 and 140% reflex threshold current). The objective CS proxy differences indicate that dorsal horn CS processes are more pronounced in healthy women. The even larger sex differences in subjective CS proxies potentially reflect greater supraspinal influence in women. This study shows that sex differences are present in experimentally induced CS in healthy subjects, which might contribute to women's vulnerability for chronic 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.

Pain perception and physiological responses are modulated by active support from a romantic partner

As social animals, humans are strongly affected by social bonds and interpersonal interactions. Proximity and social support from significant others may buffer the negative outcomes of a painful experience. Several studies have investigated the role of romantic partners' support in pain modulation, mostly focusing on tactile support and showing its effectiveness in reducing pain perception. Nevertheless, no study so far has investigated the role of supportive speaking on pain modulation, nor has compared the effects of a tactile and vocal support within the same couples. The present study directly compared for the first time the efficacy of mere presence (Passive Support) and different forms of active (Touch, Voice, Touch + Voice) support from a romantic partner during a painful experience in a naturalistic setting. We assessed pain modulation in 37 romantic couples via both subjective (self-reported ratings) and physiological (skin conductance) measurements. We found that all three types of active support were equally more effective than passive support in reducing the painful experience at both subjective and physiological levels; interestingly, our results suggest that supportive speaking can reduce pain perception with respect to passive support to a similar extent as tactile support does. Overall, this study highlights the relevance of an active support in reducing pain perception, with active types of support being more effective than passive support, regardless of its specific modality.

Distress and Resilience Narratives within Pain Memories of Adolescents and Young Adults with Complex Regional Pain Syndrome: A Multi-Method Study

A comprehensive understanding of pain memories requires consideration of risk and resilience factors across biopsychosocial domains. Previous research has typically focused on pain-related outcomes, largely ignoring the nature and context of pain memories. Using a multiple-method approach, this study explores the content and context of pain memories in adolescents and young adults with complex regional pain syndrome (CRPS). Recruited via social media and pain-related organizations, participants completed an autobiographical pain memory task. Two-step cluster analysis was conducted on the pain memory narratives of adolescents and young adults with CRPS (n=50) using a modified version of the Pain Narrative Coding Scheme. Narrative profiles generated from the cluster analysis subsequently guided a deductive thematic analysis. Cluster analysis identified two narrative profiles of Distress and Resilience, with the role of coping and positive affect emerging as important profile predictors across pain memories. Subsequent deductive thematic analysis, utilizing Distress and Resilience codes, demonstrated the complex interplay between affect, social, and coping domains. Findings highlight the importance of applying a biopsychosocial framework to pain memory research, accounting for both risk and resilience perspectives and encourage the use of multiple method approaches to improve understanding of autobiographic pain memories. Clinical implications of reframing and recontextualizing pain memories and narratives are discussed, and the importance of exploring the origins of pain and possible application to developing resilience-based, preventative interventions is highlighted. PERSPECTIVE: Using multiple methods, this paper presents a comprehensive account of pain memories in adolescents and young adults with CRPS. Study findings promote the importance of adopting a biopsychosocial approach to examining both risk and resilience factors in understanding autobiographical pain memories in the context of pediatric pain.

A partner's smile is not per se a safety signal: Psychophysiological response patterns to instructed threat and safety

Recent studies on fear conditioning and pain perception suggest that pictures of loved ones (e.g., a romantic partner) may serve as a prepared safety cue that is less likely to signal aversive events. Challenging this view, we examined whether pictures of smiling or angry loved ones are better safety or threat cues. To this end, 47 healthy participants were verbally instructed that specific facial expressions (e.g., happy faces) cue threat of electric shocks and others cue safety (e.g., angry faces). When facial images served as threat cues, they elicited distinct psychophysiological defensive responses (e.g., increased threat ratings, startle reflex, and skin conductance responses) compared to viewing safety cues. Interestingly, instructed threat effects occurred regardless of the person who cued shock threat (partner vs. unknown) and their facial expression (happy vs. angry). Taken together, these results demonstrate the flexible nature of facial information (i.e., facial expression and facial identity) to be easily learned as signals for threat or safety, even when showing loved ones.

"No pain, no gain": The impact of autonomous sensory meridian response on pain perception

Autonomous sensory meridian response (ASMR) is a phenomenon characterised by a static-like tingling sensation spreading from the scalp and neck to the periphery in response to a variety of audio, visual, and tactile triggers resulting in a highly relaxed state and boosted positive affect. The limited literature on this phenomenon points to a potential of ASMR to alleviate pain. Emerging evidence also suggests that ASMR may be linked to increased sensory sensitivity more broadly. This study aimed to objectively address these claims by administering an algometer (measure of pain tolerance), and a visual analog scale (VAS) (measure of subjective pain sensitivity) to ASMR experiencers and controls at baseline, following an ASMR video, and a control video. Findings indicate that ASMR experiencers have a higher pain sensitivity than controls; however, there was no difference between the two groups in terms of pain tolerance. In addition, any potential analgesic properties associated with experiencing ASMR may reflect protective properties of ASMR buffering against the increased pain sensitivity among ASMR experiencers relative to controls.

The induction of social pessimism reduces pain responsiveness

OBJECTIVES

Past work has found that optimism reduces a person's responsiveness to pain, but the effects of pessimism are not clear. Therefore, we gave pessimistic forecasts of participants' future social life and measured changes in their pain responsiveness. In particular, some participants were told that they would end up alone in life.

METHODS

Seventy-five subjects were investigated in three conditions (negative forecast, positive forecast, no forecast) for changes in pain threshold and pain tolerance threshold. Pressure pain induction was accomplished by either human- or machine-driven algometers. A randomly assigned bogus forecast promising either a lonely or a socially satisfying future was ostensibly based on a personality questionnaire and an emotional dot-probe task. As potential covariates, questionnaires assessing dispositional optimism (LOT-R), pain catastrophizing (PCS), and self-esteem (SISE) were given.

RESULTS

Pain thresholds suggested a change toward unresponsiveness only in the negative forecast condition, with only small differences between the modes of pain induction (i.e., human or machine). The results for pain tolerance thresholds were less clear also because of limiting stimulation intensity for safety reasons. The covariates were not associated with these changes.

CONCLUSIONS

Thus, people expecting a lonely future became moderately less responsive to pain. This numbing effect was not modulated by personality measures, neither in a protective fashion via dispositional optimism and self-esteem nor in a risk-enhancing fashion via trait pain catastrophizing. Alternative mechanisms of action should be explored in future studies.

Factors influencing postoperative pain management among nurses in selected district hospitals in Ghana

BACKGROUND

Poorly managed postoperative pain is linked to numerous postoperative complications worldwide and in Ghana. This is due to the myriad of physical and psychological problems, such as lifelong chronic pain syndromes, impaired functionality and death.

PURPOSE

The aim of this study was to assess the barriers and factors influencing postoperative pain management by Ghanaian nurses working in four hospitals.

METHODS

A quantitative descriptive cross-sectional design was employed for this study. Participants were recruited using a multistage sampling technique by which 146 returned their questionnaires out of 194 participants. The statistical analysis of data was done with the Statistical Package of Social Sciences (SPSS) 20.0 version.

RESULTS

Findings revealed that some verbal and non-verbal cues from patients such as facial grimacing, restlessness, irritability and distress, lack of concentration and moaning or crying (verbalisation) influenced how nurses controlled postoperative pain with analgesia. The participants also identified several barriers to influence postoperative pain management by nurses.

CONCLUSION

In conclusion, postoperative pain control by nurses is influenced by several factors, and hence, nurses need to manage patients' pain effectively in Ghana and abroad using multiple approaches.

The skin conductance response indicating pain relief is independent of self or social influence on pain

Pain relief is defined as the ease of pain and is thus highly relevant for clinical applications and everyday life. Given that pain relief is based on the cessation of an aversive pain experience, it is reasonable to assume that pain relief learning would also be shaped by factors that alter subjective and physiological pain responses, such as social presence or a feeling of control. To date, it remains unclear whether and how factors that shape autonomic pain responses might affect pain relief learning. Here, we investigated how pain relief learning is shaped by two important factors known to modulate pain responses, i.e. social influence and controllability of pain. Skin conductance responses (SCRs) were recorded while participants learned to associate a formerly neutral stimulus with pain relief under three different pain conditions. In the social‐influence condition (N = 34), the pain stimulation could be influenced by another person’s decisions. In the self‐influence condition (N = 31), the participants themselves could influence the pain stimulation. Finally, in the no‐influence condition (N = 32), pain stimulation was simply delivered without any influence. According to our results, the SCRs elicited by the stimulus that was associated with pain relief were significantly smaller compared to the SCRs elicited by a neutral control stimulus, indicating pain relief learning. However, there was no significant difference in the pain relief learning effect across the groups. These results suggest that physiological pain relief learning in humans is not significantly influenced by social influence and pain controllability.

The contents of this page will be shown on the eTOC on the online version only. It will not be published as part of the article PDF. Subjective and physiological pain responses can be altered by social support or pain controllability. Pain relief strongly depends on the perceived pain, but we found that it is less influenceable. Neither social nor self‐influence changed the magnitude of physiological pain‐relief responses. We conclude that pain relief is a basic mechanism not easily influenced by circumstantial manipulations.

Dyadic analysis of adolescent friendships behaviours during pain: Comparison of those with chronic pain versus those without chronic pain

BACKGROUND

Social context has been found to influence pain intensity and tolerance. The aims of this study were to determine the impact of one type of social context on the painful experiences of adolescents with and without chronic pain by examining interactions within and across friendship dyads during experimental pain.

METHODS

Each adolescent in 61 same-sex friendship dyads (30 dyads with a chronic pain member) across three sites participated in the cold pressor task and acted as the observer during their friend's participation. They also completed a battery of measures to capture friendship features and pain outcomes. Pain intensity was measured using an 11-point numeric scale. Pain tolerance was measured by the length of time in the cold pressor device. Videotapes of their interactions were coded for verbal and non-verbal behaviours. A series of Actor Partner Independence Modelling, Hierarchical Multiple Regression and Multivariate Analysis of Covariance was used to analyse the data.

RESULTS

Friendship features were not associated with pain intensity or tolerance. Both members of dyads with a chronic pain member used fewer non-attending behaviours when they were observing their friend resulting in participants in those dyads having lower pain tolerance. Moreover, within dyads, one's friend's behaviours when experiencing pain influenced pain tolerance but only for those dyads with a chronic pain member.

CONCLUSIONS

Strategies aimed at improving social interactions for adolescents with chronic pain while they are experiencing pain are discussed. Research is needed to understand how different peer relationships influence pain tolerance in adolescents with chronic pain.

SIGNIFICANCE OF THE RESEARCH

During pain, patterns of interactions differ within and between adolescent friendship dyads when one has chronic pain (CP) versus controls. Dyads with a CP member use fewer non-attending behaviours despite non-attending behaviours rated as more helpful. Pain intensity was solely related to the participant's behaviour. Amongst dyads with a CP member, pain tolerance was also influenced by their friend's behaviours. Friends of adolescents with pain engage in more unhelpful behaviours perhaps decreasing the ability of CP adolescents to engage in social activities.

Pain expectation and avoidance in the social context: an electrophysiological study

Contingent negative variation (CNV) is an informative electrophysiological measure of pain anticipation showing higher amplitudes when highly painful stimulation is expected while presenting lower amplitudes when low painful stimulation is expected. Two groups of participants were recruited: one group expected and received an electrical stimulation of different intensities while being alone in the room (i.e. without social context), while a second group performed the same experiment with an observer in the room (i.e. with social context). Lower pain ratings and slower reaction times were observed in the group with social context and these results were accompanied in this group by a lower amplitude in the early component of the CNV as well as a lower amplitude of the later component of the wave. These results show that CNV can be considered a precise measure of central elaboration of pain anticipation explaining both its perceptual and motor components.

Attentional Biases Towards Body Expressions of Pain in Men and Women

This study investigated whether there are gender differences in attention to bodily expressions of pain and core emotions. Three experiments are reported using the attentional dot probe task. Images of men and women displaying bodily expressions, including pain, were presented. The task was used to determine whether participants' attention was drawn towards or away from target expressions. Inconsistent evidence was found for an attentional bias towards body expressions, including pain. While biases were affected by gender, patterns varied across the Experiments. Experiment 1, which had a presentation duration of 500 ms, found a relative bias towards the location of male body expressions compared to female expressions. Experiments 2 and 3 varied stimulus exposure times by including both shorter and longer duration conditions (e.g., 100 vs. 500 vs. 1250 ms). In these experiments, a bias towards pain was confirmed. Gender differences were also found, especially in the longer presentation conditions. Expressive body postures captured the attention of women for longer compared to men. These results are discussed in light of their implications for why there are gender differences in attention to pain, and what impact this has on pain behaviour. PERSPECTIVE: We show that men and women might differ in how they direct their attention towards bodily expressions, including pain. These results have relevance to understanding how carers might attend to the pain of others, as well as highlighting the wider role that social-contextual factors have in pain.

The gender context of pain

Pain is a major source of global suffering, with women bearing the greatest burden. Alongside biology, psychological and social factors, including gender, help explain these differences. However, there has been no direct attempt to develop a unified social psychological model of men and women's pain. By drawing on approaches to both gender and pain, a gender context model of pain is presented. It proposes that pain is partly influenced by the gender context in which it occurs, which operates at both individual and interpersonal levels. The model is used to structure an appraisal of the existing evidence around gender and pain, and explore whether the model helps explain why such variation occurs. It is argued that despite evidence for an association between gender and pain, there are empirical gaps that need to be addressed. Implications and directions for future investigations into sex, gender and pain are considered.

Dispositional empathy is associated with experimental pain reduction during provision of social support by romantic partners

Background and aims While social interactions like verbal support and physical touch have repeatedly been shown to reduce experimental pain, analgesic effects of passive social support, i.e. the sole physical presence of a supportive other, remain unclear. Moreover, little is known about individual factors influencing the extent of pain attenuation during social support. This study investigated analgesic effects of passive support by a romantic partner and the role of partner empathy therein. Methods In 48 heterosexual couples, sensitivity to pressure pain was assessed; each participant was tested alone and in the passive presence of his/her partner. Dispositional empathy was quantified by a questionnaire. Results In the presence, as compared to absence, of their partners men and women exhibited higher pain threshold and tolerance, as well as lower sensory and affective pain ratings on constant pressure stimuli. Partner empathy was positively associated with pain tolerance and inversely associated with sensory pain experience. Conclusions The results confirm the analgesic effects of social support, which may even occur without verbal or physical contact. Partner empathy may buffer affective distress during pain exposure, thereby reducing pain sensitivity and promoting pain coping. These processes may occur solely due to a partner's physical presence and do not necessarily require direct empathetic feedback.

Testing a positive-affect induction to reduce verbally induced nocebo hyperalgesia in an experimental pain paradigm

There is an ethical obligation to notify individuals about potential pain associated with diagnoses, treatments, and procedures; however, supplying this information risks inducing nocebo hyperalgesia. Currently, there are few empirically derived strategies for reducing nocebo hyperalgesia. Because nocebo effects are linked to negative affectivity, we tested the hypothesis that a positive-affect induction can disrupt nocebo hyperalgesia from verbal suggestion. Healthy volunteers (N = 147) were randomly assigned to conditions in a 2 (affect induction: positive vs neutral) by 2 (verbal suggestion: no suggestion vs suggestion of pain increase) between-subjects design. Participants were induced to experience positive or neutral affect by watching movie clips for 15 minutes. Next, participants had an inert cream applied to their nondominant hand, and suggestion was manipulated by telling only half the participants the cream could increase the pain of the upcoming cold pressor test. Subsequently, all participants underwent the cold pressor test (8 ± 0.04°C), wherein they submerged the nondominant hand and rated pain intensity on numerical rating scales every 20 seconds up to 2 minutes. In the neutral-affect conditions, there was evidence for the nocebo hyperalgesia effect: participants given the suggestion of pain displayed greater pain than participants not receiving this suggestion, P's < 0.05. Demonstrating a blockage effect, nocebo hyperalgesia did not occur in the positive-affect conditions, P's > 0.5. This is the first study to show that positive affect may disrupt nocebo hyperalgesia thereby pointing to a novel strategy for decreasing nocebo effects without compromising the communication of medical information to patients in clinical settings.

Attentional control moderates the relationship between pain catastrophizing and selective attention to pain faces on the antisaccade task

Cognitive models of chronic pain emphasize the critical role of pain catastrophizing in attentional bias to pain-related stimuli. The aim of this study was (a) to investigate the relationship between pain catastrophizing and the ability to inhibit selective attention to pain-related faces (attentional bias); and (b) to determine whether attentional control moderated this relationship. One hundred and ten pain-free participants completed the anti-saccade task with dynamic facial expressions, specifically painful, angry, happy, and neutral facial expressions and questionnaires including a measure of pain catastrophizing. As predicted, participants with high pain catastrophizing had significantly higher error rates for antisaccade trials with pain faces relative to other facial expressions, indicating a difficulty disinhibiting attention towards painful faces. In moderation analyses, data showed that attentional control moderated the relationship between attentional bias to pain faces and pain catastrophizing. Post-hoc analyses demonstrated that it was shifting attention (not focusing) that accounted for this effect. Only for those with high self-reported ability to shift attention was there a significant relationship between catastrophizing and attentional bias to pain. These findings confirm that attentional control is necessary for an association between attentional bias and catastrophizing to be observed, which may explain the lack of relationships between attentional bias and individual characteristics, such as catastrophizing, in prior research.

Qualitative sex differences in pain processing: emerging evidence of a biased literature

Although most patients with chronic pain are women, the preclinical literature regarding pain processing and the pathophysiology of chronic pain has historically been derived overwhelmingly from the study of male rodents. This Review describes how the recent adoption by a number of funding agencies of policies mandating the incorporation of sex as a biological variable into preclinical research has correlated with an increase in the number of studies investigating sex differences in pain and analgesia. Trends in the field are analysed, with a focus on newly published findings of qualitative sex differences: that is, those findings that are suggestive of differential processing mechanisms in each sex. It is becoming increasingly clear that robust differences exist in the genetic, molecular, cellular and systems-level mechanisms of acute and chronic pain processing in male and female rodents and humans.

Self-Compassion Demonstrating a Dual Relationship with Pain Dependent on High-Frequency Heart Rate Variability

One previous study indicated the significance of trait self-compassion in psychological well-being and adjustment in people with chronic pain. Higher-frequency heart rate variability (HF-HRV) was found to be closely associated with self-compassion and pain coping. The current study was therefore designed to investigate the relationship between self-compassion and experimental pain as well as the impact of HF-HRV. Sixty healthy participants provided self-reported self-compassion and underwent a cold pain protocol during which HF-HRV was evaluated. Results demonstrated a dual relationship between self-compassion and pain, dependent on the level of HF-HRV during pain exposure. Specifically, self-compassion was associated with lower pain in the condition of higher HF-HRV, while there was an inverse relationship between self-compassion and pain when HF-HRV was lower. Our data indicate the significance of HF-HRV in moderating the association between self-compassion and experimental pain.

Exploring the relationship between male norm beliefs, pain-related beliefs and behaviours: An online questionnaire study

BACKGROUND

Gender beliefs help explain the variation found in pain among men and women. Gender norms and expectations are thought to affect how men and women report and express pain. However, less is known about how such beliefs are related to pain outside of laboratory settings. The aim of this study was therefore to consider the relationship between beliefs in male role norms, pain and pain behaviours in men and women.

METHODS

An online questionnaire study was conducted. A total of 468 adults (352 women), with or without pain, completed a series of self-report measures relating to beliefs about pain and male role norms, as well as pain and general health behaviours.

RESULTS

An experience of pain was associated with lower beliefs in traditional male norms. Endorsing stereotypical male norms was related to increased stigma associated with seeking professional help for pain in both men and women, but to a lesser extent associated with general health behaviours. There also seemed to be gender-based beliefs associated with the expression of pain.

CONCLUSIONS

Together these findings suggest that beliefs in gender (male) norms are relevant to pain, and that there is utility in exploring the variation in pain beyond binary male-female categories.

Investigating the Influence and a Potential Mechanism of Self-Compassion on Experimental Pain: Evidence From a Compassionate Self-Talk Protocol and Heart Rate Variability

Previous studies have indicated a positive relationship between self-compassion and psychological and emotional well-being in chronic pain populations. However, evidence on the role and mechanisms of self-compassion in pain perception is largely limited. The current study was designed to investigate the effects and a potential mechanism of self-compassion on experimental pain. Thirty healthy participants underwent a compassionate self-talk protocol, which was followed by cold pain exposure during which high-frequency heart rate variability (HF-HRV) was evaluated. The compassionate self-talk protocol successfully generated compassionate statements among the participants. Our behavioral data showed lower pain ratings in the self-compassion compared to the control condition. Moreover, self-compassion manipulation resulted in higher HF-HRV during pain, which was associated with lower pain ratings. We present interesting findings that a short period of compassionate self-talk may decrease experimental pain as well as mechanistic evidence surrounding bodily control over pain-related arousal indicated by HF-HRV. PERSPECTIVE: This study presents the first line of evidence that a short period of compassionate self-talk may be sufficient to reduce experimental pain. We also demonstrate increased bodily control as a potential mechanism underlying this effect.

Hide Your Pain: Social Threat Increases Pain Reports and Aggression, but Reduces Facial Pain Expression and Empathy

Earlier research studying the effects of social threat on the experience and expression of pain led to mixed results. In this study, female participants (N = 32) came to the lab with 2 confederates. Both confederates administered a total of 10 painful electrocutaneous stimuli to the participant. The framing of the administration was manipulated in a within-subjects design: In the low social threat condition the participant was told that the confederate could choose between 10 and 20 pain stimuli, thus they believed that this confederate chose to administer the minimum allowed number of pain stimuli. In the high social threat condition the confederate had a choice between 1 and 10 stimuli, thus they believed that this confederate chose to administer the maximum allowed number of stimuli. Participants reported on the intensity, unpleasantness, and threat value of the painful stimuli, and their facial expression was recorded. Moreover, aggression and empathy toward the confederates were assessed. As hypothesized, participants reported increased pain intensity, unpleasantness, and threat in the high social threat condition compared to the low social threat condition, but showed less facial pain expression. Finally, participants exhibited increased aggression and reduced empathy toward the confederate in the high social threat condition. PERSPECTIVE: Social threat reduces painful facial expression, but simultaneously increases pain reports, leading to a double burden of the person in pain. Additionally, social threat affected social relationships by increasing aggression and reducing empathy for the other.

Psychobiological Mechanisms of Placebo and Nocebo Effects: Pathways to Improve Treatments and Reduce Side Effects

Placebo effects constitute a major part of treatment success in medical interventions. The nocebo effect also has a major impact, as it accounts for a significant proportion of the reported side effects for many treatments. Historically, clinical trials have aimed to reduce placebo effects; however, currently, there is interest in optimizing placebo effects to improve existing treatments and in examining ways to minimize nocebo effects to improve clinical outcome. To achieve these aims, a better understanding of the psychological and neurobiological mechanisms of the placebo and nocebo response is required. This review discusses the impact of the placebo and nocebo response in health care. We also examine the mechanisms involved in the placebo and nocebo effects, including the central mechanism of expectations. Finally, we examine ways to enhance placebo effects and reduce the impact of the nocebo response in clinical practice and suggest areas for future research.

Neuronal and glial factors contributing to sex differences in opioid modulation of pain

Morphine remains one of the most widely prescribed opioids for alleviation of persistent and/or severe pain; however, multiple preclinical and clinical studies report that morphine is less efficacious in females compared to males. Morphine primarily binds to the mu opioid receptor, a prototypical G-protein coupled receptor densely localized in the midbrain periaqueductal gray. Anatomical and physiological studies conducted in the 1960s identified the periaqueductal gray, and its descending projections to the rostral ventromedial medulla and spinal cord, as an essential descending inhibitory circuit mediating opioid-based analgesia. Remarkably, the majority of studies published over the following 30 years were conducted in males with the implicit assumption that the anatomical and physiological characteristics of this descending inhibitory circuit were comparable in females; not surprisingly, this is not the case. Several factors have since been identified as contributing to the dimorphic effects of opioids, including sex differences in the neuroanatomical and neurophysiological characteristics of the descending inhibitory circuit and its modulation by gonadal steroids. Recent data also implicate sex differences in opioid metabolism and neuroimmune signaling as additional contributing factors. Here we cohesively present these lines of evidence demonstrating a neural basis for sex differences in opioid modulation of pain, with a focus on the PAG as a sexually dimorphic core of descending opioid-induced inhibition and argue for the development of sex-specific pain therapeutics.

A prospective study of patients’ pain intensity after cardiac surgery and a qualitative review: effects of examiners’ gender on patient reporting

Background and aims

As indicated by experimental studies, reports of pain intensity may depend on the examiner’s gender. Until now, it is unclear whether this is relevant in clinical routine. This study investigated prospectively whether the gender of assessor plays a role in patients’ pain reports and whether this role differs in male and female patients.

Methods

165 patients (66.4 years±0.63; 118 males) scheduled for heart surgery were allocated consecutively to one examiner out of four students of both genders: two females and two males (aged 24.3 years±1.7). Therefore, the following study groups were defined: Group 1: female assessors-female patients, 2: female-male; 3: male-female, 4: male-male. Using a standardized analgesic scheme, patients were asked to rank their pain intensity on a numeric rating scale (NRS: 0–10), postoperatively. Statistics: Kruskal-Wallis, Mann-Whitney; p<0.05. Additionally, a qualitative literature review of the databases Medline and CENTRAL was performed focusing on experimental and clinical studies on experimenter gender bias. Due to the review, this prospective clinical study was designed to investigate whether patients after surgery report lower pain intensities when assessed by a female compared to a male assessor.

Results

Summarizing all patients, pain intensity on POD_1 was rated 4.0±2.4 on NRS and decreased on POD_2 to 3.0±2.1 [H(3)=37.941, p=0.000]. On average, pain intensity did not differ between males and females (NRS: 3.5 vs. 3.6). Only on the second postoperative day, more intense pain was reported in front of female assessors and less intense pain in front of male assessors (NRS: 3.4 vs. 2.4; p=0.000). A main effect for the four groups was seen (p=0.003): male patients reported higher pain scores to female assessors (NRS: 3.5 vs. 2.3; p=0.000).

Conclusions

Together, contrary to the expectations, patients after cardiac surgery reported a higher pain intensity in front of a female and a lower pain intensity in front of a male assessor. In particular, female caregivers may heighten the reported pain intensity up to 1.2 NRS-points; this bias seems to be more relevant for male patients.

Implications

Therefore, despite some methodological weakness, our data suggest that attention should be paid to a rather small, but somehow significant and consistent examiner gender bias after cardiac surgery especially in male patients. Further clinical studies are needed to show the true extent of clinical relevance and exact mechanisms underlying these gender reporting bias.

Accurate empathy of romantic partners increases pain ratings but promotes recovery

Background

Perceived empathy is a commonly used strategy to cope with pain and is crucial for maintaining intimacy in dyadic relationships.

Materials and methods

This study used the cold pressor test to investigate how perceived empathy and relationship type interact with the subjective perception of pain and objective measures of recovery time, using heart rate as an index. One hundred and ninety participants were recruited, including 49 friend dyads and 46 romantic partner dyads. Perceived empathy was manipulated by adopting three levels as the experimental conditions: high, accurate, and low.

Results

In the subjective perception stage, the results showed a significant interaction of relationship type and empathy with pain reporting, indicating that romantic partners reported more pain than friends under the accurate empathy condition. There were no differences between the two groups in the high and low perceived empathy conditions. In the self-recovery stage, the results showed that romantic partners had less pain tolerance than friends in all three perceived empathy conditions. On the other hand, romantic partners recovered faster than friends under the accurate empathy condition, but not under the high and low perceived empathy conditions.

Conclusion

These results suggest that perceived accurate empathy is necessary for romantic relationships when coping with pain. The findings deepen our understanding of the mechanism of perceived empathy, and the ways in which it modulates psychological and physiological responses in a social context.

Contextual influences in decoding pain expressions: effects of patient age, informational priming, and observer characteristics

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Informational primes (about pain undertreatment or social deception) interact with observer characteristics and patient age in the interpretations of pain signals.

We aimed to examine the effects of contextual factors (ie, observers' training background and priming texts) on decoding facial pain expressions of younger and older adults. A total of 165 participants (82 nursing students and 83 nonhealth professionals) were randomly assigned to one of 3 priming conditions: (1) information about the possibility of secondary gain (misuse); (2) information about the frequency and undertreatment of pain in the older adult (undertreatment); or (3) neutral information (control). Subsequently, participants viewed 8 videos of older adults and 8 videos of younger adults undergoing a discomforting physical therapy examination. Participants rated their perception of each patient's pain intensity, unpleasantness, and condition severity. They also rated their willingness to help, sympathy level, patient deservingness of financial compensation, and how negatively/positively they feel towards the patient (ie, valence). Results demonstrated that observers ascribed greater levels of pain and other indicators (eg, sympathy and help) to older compared with younger patients. An interaction between observer type and patient age demonstrated that nursing students endorsed higher ratings of younger adults' pain compared with other students. In addition, observers in the undertreatment priming condition reported more positive valence towards older patients. By contrast, priming observers with the misuse text attenuated their valence ratings towards younger patients. Finally, the undertreatment prime influenced observers' pain estimates indirectly through observers' valence towards patients. In summary, results add specificity to the theoretical formulations of pain by demonstrating the influence of patient and observer characteristics, as well as informational primes, on decoding pain expressions.

The Social Regulation of Pain: Autonomic and Neurophysiological Changes Associated With Perceived Threat

The analgesic effect of social support is proposed as a function of social support modulating perceived threat of painful stimuli. In the current study, we directly examined the social buffering effect in the context of the threat of pain. Eighteen healthy participants were subjected to the threat of pain while they held the hand of a close other, a stranger, or not at all. Neural and autonomic responses were recorded using electroencephalogram and heart rate, respectively. Close other hand-holding reduced pain perception. This was accompanied by decreased heart rate and frontal theta oscillation (4-8 Hz) during the threat phase preceding painful stimulation. Interestingly, decreased heart rate and frontal theta in the close other hand-holding condition were uniquely associated with greater pain reduction during subsequent nociceptive stimulation. Neural changes were source-localized to the insular cortex and the rostral-ventral portions of anterior cingulate cortex, regions involved in the processing of threat and pain. Together, our data build upon work to date linking social support to pain by showing autonomic and neurophysiological changes associated with pain reduction.

PERSPECTIVE

Social support may reduce pain through buffering the autonomic and neurophysiological response to the threatening quality of noxious stimuli. Results implicate that in clinical settings the caregiver could help people with chronic pain reappraise pain and related conditions as less stressful.

Social interaction and pain: An arctic expedition

Complex human behaviour can only be understood within its social environment. However, disentangling the causal links between individual outcomes and social network position is empirically challenging. We present a research design in a closed real-world setting with high-resolution temporal data to understand this interplay within a fundamental human experience - physical pain. Study participants completed an isolated 3-week hiking expedition in the Arctic Circle during which they were subject to the same variation in environmental conditions and only interacted amongst themselves. Adolescents provided daily ratings of pain and social interaction partners. Using longitudinal network models, we analyze the interplay between social network position and the experience of pain. Specifically, we test whether experiencing pain is linked to decreasing popularity (increasing isolation), whether adolescents prefer to interact with others experiencing similar pain (homophily), and whether participants are increasingly likely to report similar pain as their interaction partners (contagion). We find that reporting pain is associated with decreasing popularity - interestingly, this effect holds for males only. Further exploratory analyses suggest this is at least partly driven by males withdrawing from contact with females when in pain, enhancing our understanding of pain and masculinity. Contrary to recent experimental and clinical studies, we found no evidence of pain homophily or contagion in the expedition group.

Sex-specific effects of intranasal oxytocin on thermal pain perception: A randomised, double-blind, placebo-controlled cross-over study

Chronic neck and shoulder pain (CNSP) is a common musculoskeletal disorder in adults, which is linked to hypersensitivity to noxious stimuli. The hormone oxytocin has been implicated as a potential therapeutic for the management of chronic pain disorders, and has been suggested to have sex-specific effects on the salience of threatening stimuli. This study investigated the influence of intranasal oxytocin on the perception of noxious thermal stimuli. Participants were 24 individuals with CNSP lasting >12months (eight women), and 24 age- and sex-matched healthy, pain-free controls. In a randomised double-blind, placebo-controlled, cross-over study, participants attended two sessions, self-administering intranasal oxytocin (24 IU) in one session, and placebo in another. Participants rated intensity and unpleasantness of thermal heat stimuli at three body sites: the cervical spine, deltoid, and tibialis anterior, on 11-point numerical rating scales. Compared with placebo, intranasal oxytocin increased the perceived intensity of noxious heat stimuli in women with CNSP (Cohen's d=0.71), but not in men with CNSP, or healthy, pain-free controls. Men and women displayed divergent sensitivity across target sites for ratings of pain intensity (partial eta squared=0.12) and pain unpleasantness (partial eta squared=0.24), irrespective of drug condition. Men were more sensitive at the cervical spine and deltoid, whereas women were more sensitive at the tibialis. These findings suggest that oxytocin and endogenous sex hormones may interact to influence the salience of noxious stimuli. The hyperalgesic effects of oxytocin in women suggest that caution should be taken when considering oxytocin in the management of chronic pain.

TRIAL REGISTRATION

CT-2016-CTN-01313-1; ACTRN12616000532404.

Psychosocial factors and their influence on the experience of pain

Over the past 20 years, our understanding of social factors on pain experience has increased. Edwards et al observed that the presence of a friend resulted in an increased pain threshold and tolerance to experimentally induced pain (cold pressor test and pressure algometry). Having a male friend present had the most prominent effect on male participants' reporting of pain. However, the effects of psychosocial traits known to effect pain experience (eg, catastrophising) were not considered.

Contextual influences on pain communication in couples with and without a partner with chronic pain

This is an experimental study of pain communication in couples. Despite evidence that chronic pain in one partner impacts both members of the dyad, dyadic influences on pain communication have not been sufficiently examined and are typically studied based on retrospective reports. Our goal was to directly study contextual influences (ie, presence of chronic pain, gender, relationship quality, and pain catastrophizing) on self-reported and nonverbal (ie, facial expressions) pain responses. Couples with (n = 66) and without (n = 65) an individual with chronic pain (ICP) completed relationship and pain catastrophizing questionnaires. Subsequently, one partner underwent a pain task (pain target, PT), while the other partner observed (pain observer, PO). In couples with an ICP, the ICP was assigned to be the PT. Pain intensity and PO perceived pain intensity ratings were recorded at multiple intervals. Facial expressions were video recorded throughout the pain task. Pain-related facial expression was quantified using the Facial Action Coding System. The most consistent predictor of either partner's pain-related facial expression was the pain-related facial expression of the other partner. Pain targets provided higher pain ratings than POs and female PTs reported and showed more pain, regardless of chronic pain status. Gender and the interaction between gender and relationship satisfaction were predictors of pain-related facial expression among PTs, but not POs. None of the examined variables predicted self-reported pain. Results suggest that contextual variables influence pain communication in couples, with distinct influences for PTs and POs. Moreover, self-report and nonverbal responses are not displayed in a parallel manner.