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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 31  |  Issue : 1  |  Page : 59-64

Pain-relevant anxiety affects desire for pain relief, but not pain perception


1 Department of Diagnostic Radiology, Yong Loo Lin School of Medicine, National University of Singapore 119228, Singapore
2 University of Split School of Medicine, Soltanska 2, 21000 Split, Croatia

Date of Web Publication5-May-2017

Correspondence Address:
Adriana Banozic
Department of Diagnostic Radiology, Yong Loo Lin School of Medicine, National University of Singapore, 119228
Singapore
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijpn.ijpn_72_16

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  Abstract 


Background: Pain context plays a significant role in the perception of pain. Despite recent interest in vicarious learning and anxiety in pain modulation, there have been no attempts to explore pain modulation by specific environmental cues. Aims: Therefore, the present study evaluated pain responses in the condition that was attributed as either anxiety relevant (AR) or anxiety irrelevant. Materials and Methods: Participants were exposed to both conditions through social observational learning. Pain perception was assessed by means of a visual analog scale ranging from 0 = no pain to 10 = maximum imaginable pain. State anxiety, empathy, expectancy, and desire for pain relief were also measured at both neutral and emotionally inducing conditions. Results: No effect of relevancy of anxiety for the pain context on any of the pain-related constructs was found. However, participants in the AR condition reported an increased desire for pain relief. Maximizing similarities between observed and experienced pain context did not enhance observational learning effects in the emotionally inducing condition regardless of its relevance, but significant changes were found in comparison to the affectively neutral group. Conclusions: These results could have potentially significant clinical implications suggesting that even though observing painful procedures does not increase pain it could affect medication usage.

Keywords: Anxiety, context, desire for pain relief, experimental thermal pain, pain, social observational learning


How to cite this article:
Banozic A, Beljan I. Pain-relevant anxiety affects desire for pain relief, but not pain perception. Indian J Pain 2017;31:59-64

How to cite this URL:
Banozic A, Beljan I. Pain-relevant anxiety affects desire for pain relief, but not pain perception. Indian J Pain [serial online] 2017 [cited 2019 Dec 6];31:59-64. Available from: http://www.indianjpain.org/text.asp?2017/31/1/59/205723




  Introduction Top


Individuals' experience of pain is a product of numerous interactions of affective, motivational, and cognitive components.[1] Among affective mediators, anxiety has been of great interest.[2],[3],[4],[5] Characterized by feelings of apprehension about impending harm, anxiety is a central part of pain experience.[6]

Although a considerable amount of studies have shown anxiety to enhance pain sensitivity,[7],[8] both theoretical and empirical accounts have suggested the nature of that relationship to be far from simple.[2] Two theoretical models have been proposed to explain the role of anxiety and experimental context in pain: attributional and attentional.[9]

According to the attributional model, pain-relevant (PR) anxiety leads to increased pain responses, while pain-irrelevant (PI) anxiety decreases pain responses. Weisenberg et al. have suggested that PR increases pain reports due to arousal that accompanies anxiety and is attributed to pain.[10] Conversely, PI reduces pain responses because of arousal that is attributed to factors other than pain stimuli.[11] Attentional theory, on the other hand, focuses on the role of distraction in reducing the pain,[12],[13] operating under the assumption that activities that allocate attention away from the painful stimulus diminish the attentional capacity for processing of pain.[14] Arntz et al. further explored the mediating role of attribution and attention for relevancy of pain anxiety and found that subjective pain responses could be mainly explained by attentional processes.[9]

It should be considered that all these processes take place in a social context, so observing pain undeniably affects the observer.[15] Several human studies showed that the exposure to an actor in pain [16],[17] or even the simple observation of pictures of human pain [18],[19] is associated with higher pain reports. Recent studies demonstrated that empathy regardless of the observation of pain behavior alters both pain intensities and unpleasantness ratings.[15],[20],[21] These findings may have profound implications in clinical settings,[19] since patients in clinical trials could be influenced by observing the behavior of other patients and consequently change the treatment outcomes.[6],[21]

Empathy greatly relies on context, and in every empathic process, contextual cues retrieve previous experiences to manage internal (previous experiences) and external (situation appraisal) processes.[22],[23] The aim of the present study, therefore, was to evaluate the effects of relevancy of anticipatory anxiety. We predicted that observing pain in an anxiety-relevant (AR) condition would increase observers' own pain ratings while they would remain completely unaffected by PI condition. Second, we have predicted that observers would be more empathic toward an actor who was in an AR situation when compared to the anxiety-irrelevant (AI) condition, due to the salience of environmental cues.


  Materials and Methods Top


Participants

Participants were recruited through advertisements on the University of Gothenburg bulletin boards. A total of 18 right-handed students (mean age: 22.82 ± 4.41) participated in the study. All participants were screened for a history of psychiatric or neurological conditions and whether they were free of pain or pain medication. They were randomly assigned to two groups with the restriction that there were the same proportions of males and females in each condition. All participants provided informed consent. Ethical approval was obtained through the Institutional Review Board of the University of Gothenburg and Sahlgrenska University Hospital. Participants were financially compensated for their participation.

Testing paradigm

Participants were familiarized to the thermal stimuli in a practice session before formal pain sensitivity testing. In each condition, a series of seven painful (45°C–50°C) stimuli were delivered on the dorsal side of the participants' forearm through a 50 mm × 70 mm contact thermode (TSA II Neuro-Sensory analyzer, Medoc Ltd., Advanced Medical System, Israel). Specific components of pain sensitivity were assessed including (1) threshold and (2) intensity ratings; visual analog scale (VAS) was used to evaluate pain stimuli ranging from 0 (no pain) to 10 (worst pain imaginable). Each stimulus lasted 4 s (1 s to reach the target temperature, 2 s at plateau, and 1 s to return to the baseline temperature) [Figure 1].
Figure 1: Schematic representation of the study design. Participants' sensitivity to painful stimuli was measured following the exposure to a neutral video - baseline (actor talking about the research capacities of the University of Gothenburg). Next, participants were asked to watch a video of an actor participating in either pain experiment or struggling to give a public speech, followed by a second thermal testing session (which was performed after participants watched the videos). Finally, postexperimental questionnaires were presented to the participants

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In the first session (“baseline” testing session), pain threshold was estimated, after which participants were presented with the “neutral” video. This video featured a student talking about research capacities of the University of Gothenburg and was selected for its affective neutrality on the basis of the judgments of five participants who participated in a preliminary material testing. Empathy, anxiety, and expectancy measures were taken following the video. In the next session, participants watched either a video designed to induce anxiety, in which the actor was very expressive of pain, or a video evaluated as affectively negative featuring the same actor but in a manner unrelated to pain experience (an anxious student giving a public speech). Both videos were specifically designed to induce anxiety, but only one with the relevant context (experimental setting and an individual exposed to pain stimuli), the second one was set up in the AI context (actor giving a public speech) and were evaluated as affectively negative in preexperimental testing. To ensure that participants would be attentive to the videos, we asked them to count the number of certain behavioral parameters such as hand movements and changes of body posture.

After the final series of pain stimuli, participants were fully debriefed and asked to evaluate the credibility of the actor in video.

Psychological instruments

Participants were instructed to rate the intensity of each painful thermal stimulus after its presentation. Participants were required to click on a VAS or a box presented on the screen of the computer. All psychological measures were preprogramed and presented for participants on the computer screen using MATLAB. After watching video, participants rated pain expectancy levels, matched expectations, desire for pain relief, anticipatory anxiety, state empathy, and credibility of an actor in a video on VAS scales [Figure 2].
Figure 2: Visual analog scales used during the experiment. After the baseline testing sessions, as well as after observations, participants rated their anxiety, expectancy, and empathy levels. Actors playing in the videos were presented to the participants as another participant in the experiment and referred to as a “model” throughout the experiment

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Mood

Mood was measured with Swedish version of Mood scale [24] at three time points during each session: (1) before watching videos, (2) after watching videos, and (3) following pain stimulation. Participants rated their current level of fear, sadness, irritability, happiness, calmness, and anxiety using VAS with anchors (0) “Not at all” to (100) “Very much so.”

Observed behavior

Participants were asked to evaluate the behavior of an actor in a video on a list of five adjectives selected specifically for this study (adjectives were selected based on assessments of five participants in a pretesting condition) as follows: aggressive/happy/calm/sad/comfortable. Ratings of actors' behavior were obtained using a VAS scale ranging from 1 to 10.

At the end of an experiment, a single item was added to examine the credibility of an actor in video on a VAS scale ranging from (0) “Not at all” to (10) “Very much so.”

State empathy

State empathy measure consisted of adjectives reflecting empathic concern (concerned, warm, empathic, compassionate, soft hearted) that participants responded to a 5-point scale ranging from “does not at all describe how I feel” (1) to “describes how I feel extremely well” (10). These adjectives were based on the scale by Batson et al.[25] and adjusted for this study.

Pain expectancy

Expected pain intensity was measured by asking the participants: “What do you expect your level of pain intensity to be during this session?” Expected pain ratings would be obtained using the VAS that was used to assess actual pain intensity ranging from (0) “No pain” to (10) “Worst pain imaginable.” A single item “Has the previously experienced pain level matched with your expectations” was added in each stage to test for matched expectations.

Desire for pain relief

Desire for pain relief was measured by asking the patients: “How strong is your desire for pain relief?” Ratings of desire for relief would be obtained with VAS scales anchored by the descriptors “no desire for pain relief” (0) and “the most intense desire for relief imaginable” (10).

Anticipatory anxiety

Anxiety was measured by asking the patients: “How anxious are you about the pain you may experience during this session?” Ratings of anxiety were obtained with VAS scales anchored by the descriptors “no anxiety” (0) and “the most intense anxiety imaginable” (10).

These scales for expected pain levels, matched expectations, desire for pain relief, and anticipatory anxiety have been validated previously.[26]

Trait anxiety

Trait anxiety was assessed in the baseline appointment with the Swedish version of the State-Trait Anxiety Inventory.[27] Trait version consists of 20 self-descriptive statements concerning different anxiety symptoms. For the trait version, participants had to indicate how they feel in general on a scale ranging from 1 (“almost never”) to 4 (“most of the time”). In our sample, trait anxiety demonstrated good internal consistency (Cronbach's α = 0.83).

Trait empathy

Trait empathy refers to the dispositional tendency to respond empathically to day-to-day life situations. Participants were asked to complete a Swedish translation of the Balanced Emotional Empathy Scale,[28] a commonly used trait empathy questionnaire. It consists of 30 items using a 9-point agreement–disagreement scale. A single item “Unhappy movie endings haunt me for hours afterward.”

Hypotheses

It was expected that participants in AR (pain experiment) versus AI (public speech) context would be more sensitive to thermal pain. Furthermore, a positive correlation was expected between pain expectancy, pain reports, and anticipatory anxiety in the experimental condition, and also significant differences were expected between these psychological variables in neutral condition versus experimental condition. Participants' pain expectancy in the AR condition is expected to match their pain reports, but not in the AI condition. It was also hypothesized that participants would be more empathic toward an actor in the AR condition versus AI condition.

Data analysis

To test the hypotheses, the mean pain intensity score was calculated, and a 2 × 2 mixed ANOVA with the between-subject factor condition (condition [AR or AI]) and the within-subject neutral versus experimental pain intensity, anxiety, and expectancy was computed. Least significant difference post hoc tests were used for further analyses. Given that mood changes affect the pain perception,[29] we examined changes in affect throughout the entire experiment. Univariate comparisons for traits (empathy, anxiety) would be performed using t-tests. Pearson's correlations were computed for pain expectancy, anxiety, and pain reports in experimental conditions. The level of significance was set at P< 0.05. All analyses were performed using SPSS software version 20.0. (IBM Corp., Armonk, NY, USA).


  Results Top


The groups did not differ on any of the psychological traits of either empathy or anxiety [Table 1]. Mood was stable throughout the experiment, and average mood rating was 74.12 ± 8.73. A separate repeated-measures ANOVA was conducted on the mood ratings on three separate time points with condition as a between-subjects factor and no significant effect was found (F(2,30) = 0.75, mean squared error [MSE] = 2.12, P > 0.05). The 2 × 2 repeated-measures ANOVA showed no main effect for pain intensity between groups (F(1,14) = 0.63 MSE = 0.49, P > 0.05) or within groups (F(2,28) = 0.385 MSE = 0.49, P > 0.05) although there is a tendency toward an increase in pain sensitivity of the experimental group. The same tendency was present for state empathy as well [Figure 3]. Neither age nor gender proved to be significant covariate in any of the comparisons (P > 0.05).
Table 1: Mean test scores of participants in control and experimental conditions and results of their pair-wise comparisons

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Figure 3: Mean pain ratings as a function of condition (anxiety relevant [experimental] and irrelevant [control]) (a); mean ratings on empathy scale for anxiety relevant (experimental) and irrelevant [control condition]) (b)

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No differences in pain expectancy were observed between the AR and AI groups (F(1,15) = 0.003, MSE = 0.385, P > 0.05), but it was evident that participants overestimated the accuracy of their expected pain ratings in the experimental conditions compared to the neutral condition (F(1,15) = 8.095, MSE = 0.65, P< 0.05). Participants were equally empathic for the actor in both AR and AI videos (F(1,13) = 3.12, MSE = 2.39, P > 0.05). However, following the AR video, participants reported significantly stronger desire for pain relief in comparison to participants in the AI condition (t(15) = 2.60, MSE = 0.35, P< 0.05).

Actors in both anxiety conditions were evaluated as equally credible. However, significant differences were observed across all descriptors between experimental and neutral videos, for which the actor was mainly described as calm and comfortable. Participants in both anxiety conditions mainly described the behavior of the actor in videos as sad (5.11 ± 2.06) and comfortable (1.47 ± 2.15) which was also the only descriptor that differentiated between groups (t(15) = 2.43, standard error of the mean = 0.52, P< 0.05).


  Discussion Top


This study investigated the effects of the relevancy of anxiety on pain perception. Contrary to the initial hypothesis, participants in the AR versus AI condition (stressful public speech context) did not differ with respect to their pain ratings. Second, they were equally anxious and empathic toward the model and in both AR and AI conditions. Participants in AR group slightly overestimated the accuracy of their pain reports and following pain stimulation reported stronger desire for relief.

The results of the present study suggest that the pain relevance of anxiety did not have any additional influence on the subjective pain experience. Taken together, neither expectancy nor anticipatory anxiety had any effect on pain reports even when controlled for trait anxiety. Thus, the theory that attributional processes function as a mediator between anxiety and pain perception [10] was not supported. In light of our findings, another theoretical approach, emphasizing the focus of anxiety, as suggested by Colloca and Benedetti,[30] should be considered. Whether anxiety would result with pain decrease or increase largely depends on the focus of anticipatory anxiety. If anticipatory anxiety is focused on pain itself, it is likely that hyperalgesia would occur. On the other hand, if anticipatory anxiety is focused on some other environmental cues, analgesia is more likely to occur. In this study, we wanted to ensure participants' attention while watching videos, so they were instructed to memorize the behavioral parameters of an actor in video (hand movements, change of a body posture…). Therefore, it is possible that the memory task, instead of focusing participants' attention, actually functioned as a distractor that masked the effect of anticipatory anxiety. Anticipatory cues are also an important determinant of expectancy effects on pain perception. Our results did not support the role of expectancy in predicting pain reports. On the other hand, desire for pain relief and expected pain levels are known to be related in a vast majority of placebo literature.[31] In our study, quite surprisingly, desire proved to be the only factor that differentiated between experimental groups even though it was unrelated to either pain or expectancy. Desire for pain relief is considered as a particular psychological mindset that contributes to pain experience, and elevation in negative emotions is known to sustain it. In that respect, our results consistently show elevated pain expectancy and anxiety scores in AR group even though it failed to reach statistical significance, opposite to desire for pain relief which exhibited a strong effect.

In our study, the participants did not differ in the levels of empathy toward an actor in either video. Even though they recognized actors in AR and AI videos as more distressed than actors in the neutral video, that effect did not influence the levels of empathy.

Although previous studies suggested that empathy modulates pain responses and not observation,[21] our results have not provided evidence for either alternative.

Previous research reported that observing pain elicits distress in participants.[32] Furthermore, observing pain can elicit pain response in others as reported by Osborn and Derbyshire;[20] however, the mechanisms and conditions that characterize vicarious pain are still largely unknown. Overall, it is possible that relatively low response of vicarious pain reported in AR condition was due to limited number of participants largely due to financial and ethical constraints. Furthermore, we realize that any experimental pain setting loses some of its face validity because real-life pain is often more ambiguous and threatening.

In addition, although participants evaluated the actor in videos as credible, both groups in the debriefing session reported that they could easily identify themselves with him/her and considered public speech just as distressing, so it could be inferred that, what we considered irrelevant for pain, most of our participants perceived as very relevant to their everyday college experiences.


  Conclusion Top


The results of this study showed no effect of relevancy of pain context on any of the pain-related constructs. We also found evidence that maximizing similarities between model and its context and the observer and its context did not enhance observational learning effects and consequently experienced pain. However, significant difference in desire for pain relief but no changes in pain ratings could have considerable implications on the usage of analgesic medications, as well as the final therapeutic response.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Acknowledgments

This work was supported by the Swedish Research Council project grant number 2010-2120.

Financial support and sponsorship

This work was funded by the Swedish Research Council project grant number 2010-2120.

Conflicts of interest

There are no conflicts of interest.



 
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