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. Author manuscript; available in PMC: 2021 Jul 1.
Published in final edited form as: Clin J Pain. 2020 Jul;36(7):562–566. doi: 10.1097/AJP.0000000000000829

Pressure pain tolerance predicts the success of emotional awareness and expression therapy in patients with fibromyalgia

Tiffany Bellomo 1, Andrew Schrepf 1, Grant H Kruger 1,2, Mark A Lumley 3, Howard Schubiner 4,5, Daniel J Clauw 1, David A Williams 1, Steven E Harte 1
PMCID: PMC7272255  NIHMSID: NIHMS1580174  PMID: 32271184

Abstract

Objectives

Quantitative sensory testing (QST) may help predict treatment responses in individuals with chronic pain. Our objective was to determine if evoked pain sensitivity at baseline predicted preferential treatment responses to either emotional awareness and expression therapy (EAET) or cognitive behavioral therapy (CBT) in individuals with fibromyalgia.

Methods

This was a secondary analysis of a previous randomized clinical trial, in which individuals with fibromyalgia were randomized to EAET, CBT, or Education as a control intervention. Only females who completed baseline and post treatment assessments were analyzed (n = 196). The primary outcome was change in overall clinical pain severity from pre-treatment to post-treatment, and the primary predictor of interest was pressure pain tolerance at baseline.

Results

Among patients with low pain tolerance at baseline (n = 154), both EAET and CBT led to small but significant improvements in clinical pain severity (CBT mean [95% CI] = 0.66 [0.24, 1.07]; EAET = 0.76 [0.34, 1.17]). Conversely, in patients with normal pain tolerance (n = 42), there was no significant improvement in clinical pain after CBT (0.13 [−0.88, 1.14]), a small improvement after FM Education (.81 [.14, 1.48]), but a much larger and statistically significant improvement after EAET (2.14 [1.23, 3.04]).

Discussion

Normal levels of pressure pain tolerance at baseline predicted greater improvement in clinical pain severity following EAET than CBT. QST may provide insights about individual responses to psychologically-based therapies for individuals with chronic pain.

Keywords: Fibromyalgia, Emotional Awareness and Expression Therapy, Cognitive Behavioral Therapy, Patient Education, Chronic Pain, Pain Perception

INTRODUCTION

Fibromyalgia (FM) is a chronic widespread pain condition affecting 2 to 8% of the population1,2. There is strong evidence that FM involves central nervous system pain amplification and is characterized primarily by multifocal pain as well as energy, memory, sleep, and mood disturbances2–5. Only a minority of individuals with FM respond well to the approved pharmacological treatment options, necessitating a reliance on non-pharmacologic approaches2–5. Such non-pharmacological approaches address complex neurobiological, psychological, and behavioral factors and focus on reducing key symptoms, increasing daily function, and improving mood3,6. Some of the most promising psychotherapies for FM include cognitive behavior therapy (CBT) and a more recent approach, emotional awareness and expression therapy (EAET)3–5.

CBT is the most thoroughly researched psychotherapy for FM and focuses on teaching patients skills to better manage their symptoms and improve functioning; meta-analytic reviews indicate that CBT is only of relatively modest benefit to individuals with chronic pain1–3,5. Given the role that psychological trauma and emotional conflict play in FM, EAET was developed to directly address these factors by engaging patients in emotional processing and corrective emotional experiences1,7–10. We recently completed a randomized clinical trial comparing EAET, CBT, and an active control condition—FM Education—for the treatment of FM. EAET significantly outperformed FM Education on most outcome measures, whereas the effects of CBT were more limited in magnitude. Although group level improvement was observed, only 23% of participants in the EAET arm, 8% in the CBT arm, and 12% in the FM Education arm reached a 50% reduction in clinical pain severity11. These and other data suggest that only a subset of chronic pain patients respond well to any given therapeutic intervention 5,11,12.

Efforts are currently underway to identify symptoms, traits, and neurobiological correlates associated with FM, particularly those that might help predict treatment response1,2,4,5,13. Quantitative sensory testing (QST), which is a set of standardized psychophysical methods to measure sensory function, has been used extensively to assess pain sensitivity in clinical populations, including FM14–19, and more recently to predict response to surgical and pharmacological treatments for pain20–22. However, the association between QST and psychotherapeutic outcomes has not been explored. Here we analyzed pre-treatment pressure pain tolerance measured by QST from the above described clinical trial of EAET, CBT, and FM Education to determine if pain sensitivity measured at baseline predicted differential treatment responses. Identifying FM patients more likely to respond to particular psychologically-based therapies may help tailor treatment decisions to improve patient outcomes as well as advance our understanding of therapy mechanisms.

METHODS

Participants

All data were extracted for secondary analysis from a previously described randomized control trial assessing the outcomes of EAET, CBT, and FM Education for FM patients11. This study was conducted at Wayne State University (Detroit, MI) and the University of Michigan (Ann Arbor, MI). FM status was assessed by medical history and confirmed by the 2011 FM survey criteria or the 1990 ACR criteria23,24. Exclusion criteria were pending or recent litigation or disability application, non-English speaking, co-morbid autoimmune disorders or serious medical conditions, and inappropriateness for group participation (e.g., severe mental health problems). QST was conducted prior to randomization and the initiation of treatment. Additional information about randomization and each treatment is arm is available from the primary publication11. The present study examined the subset of patients who completed both the baseline assessment and the post-treatment assessment, allowing us to capture treatment effects over time. Because there were too few males (n = 11) enrolled in the study to draw reliable inferences, we excluded them from the subsequent analyses. This resulted in 196 women with FM for the present analysis of out a total of 230 participants in the original study. All procedures were approved by the IRB at each participating institution, and all participants provided written informed consent.

Measures

Primary predictor: Pressure pain tolerance

Pressure pain tolerance was assessed at the thumbnail following well-described procedures25–29, using the Multimodal Automated Sensory Testing (MAST) system (Arbor Medical Innovations, Ann Arbor, MI)13. Prior to data collection, participants underwent a familiarization procedure and practice testing on their non-dominant thumb to reduce test anxiety. The MAST system automated the delivery of a series of discrete 5-s pressures using an electro-mechanical 1cm2 rubber tipped probe, starting with a peak intensity of .50 kgf/cm2 and increasing in .50 kgf/cm2 steps for subsequent stimuli (20-s inter-stimulus interval). Closed-loop control was used to maintain a 4.0 kgf/s ramp rate as well as the constant pressure portion of each stimulus. Patients rated the intensity of the stimuli on 0–100 numerical rating scales, 100 representing ‘worst pain imaginable.’ Testing ended when: a) the patient reached his/her self-reported pain tolerance, b) the patient reported a pain intensity of ≥ 80/100, or c) a maximum possible pressure of 10 kgf/cm2 was delivered. Pressure pain tolerance was calculated as the last pressure delivered and rated by each participant. A majority of FM patients are known to have widespread hyperalgesia, reflecting central neurobiological sensitization1,30; however, a small subset of FM patients lack this characteristic31. To understand if pain tolerance plays a role in the varying responses to psychologically-based therapies, patients were subsequently categorized into “normal tolerance” or “low tolerance” groups. “Normal tolerance” was defined as 5.5 kgf/cm2 or greater, as this level is consistent with the mean tolerance for healthy women in two large multi-site studies that employed the MAST device using the same protocol as the current study to measure pain sensitivity32,33.

Primary outcome: Clinical pain severity

The primary outcome was change in clinical pain severity measured by the Brief Pain Inventory34 between study entry and completion of therapy34. This measure is a composite of participants’ self-reported current pain as well as their worst, average, and least pain over the last week.

Other baseline characteristics

At baseline, the 2011 FM survey criteria was used to assess diffuse pain as well as the presence and severity of comorbid symptoms35. The SF-36 physical function composite survey assessed physical functioning and quality of life36, with higher scores indicating better functioning. The Center for Epidemiological Studies –Depression (CESD) scale assessed depressive symptoms37, with higher scores indicating more depressive symptoms. Finally, the Coping Strategies Questionnaire (CSQ) catastrophizing subscale measures catastrophic thinking about pain, with higher scores indicating more catastrophizing38.

Statistical Analysis

Descriptive characteristics were performed, including demographics and levels of symptoms at study entry. Pearson correlations were used to determine if pressure pain tolerance was associated with baseline symptoms.

To examine the interaction between treatment assignment and pressure pain tolerance on the magnitude of change in clinical pain severity following treatment, a general linear regression model was used. In this model the dependent variable was the change score in clinical pain severity (BPI pain severity post treatment - BPI pain severity pre-treatment). Age, levels of pain, pain catastrophizing, depression, and baseline levels of clinical pain severity were entered as covariates. Main effects were treatment assignment and pressure pain tolerance group (“normal tolerance” and “low tolerance”). The model additionally included an interaction term for treatment assignment*pressure pain tolerance group. All analyses were conducted in SPSS 25 (IBM, Armonk, New York, USA).

RESULTS

Participants (n = 196) were 49.70 (SD = 11.88) years old on average, primarily white (77%), and with an average of approximately 15 years of education. At baseline, patients reported moderate-to-high levels of FM symptoms, pain catastrophizing, depression and overall pain severity (Mean[SD], FM survey score = 20.63 [4.50]; pain catastrophizing = 2.65 [1.53]; depression = 21.94 [12.32]; pain severity = 5.38 [1.63]).

Pressure pain tolerance at baseline was not associated with pre-treatment FM survey criteria scores (r = −.13; p = .08) or BPI pain severity (r = - .02; p = .79). However, normal pressure pain tolerance at baseline was associated with lower levels of depression (r = −.25; p <.001), lower levels of pain catastrophizing (r = −.23; p = .001), and greater physical functioning (r = .19; p = .007).

Patients with low pain tolerance and with normal pain tolerance underwent the following treatments: EAET (n = 57, 11), CBT (n = 51, 10), FM Education (n = 46, 21), respectively. The magnitude of change in clinical pain severity following treatment differed significantly by treatment assignment and pain tolerance group as well as by levels of pain catastrophizing (main effects, all p < .05). More importantly, there was a significant interaction effect between treatment assignment and pain tolerance group (p < .05). All parameter estimates are shown in Table 1. Figure 1 shows the estimated marginal means for clinical pain severity improvement by treatment and pain tolerance group. Among patients with low pain tolerance at baseline (n = 154), both EAET and CBT led to small but significant improvements in clinical pain severity (CBT mean [95% CI] = .66 [.24, 1.07]; EAET = .76 [.34, 1.17]). Conversely, in patients with normal pain tolerance (n = 42), there was no significant improvement in clinical pain after CBT (.13 [−.88, 1.14]), a small improvement after FM Education (.81 [.14, 1.48]), but a much larger and statistically significant improvement after EAET (2.14 [1.23, 3.04]).

Table 1.

Parameter estimates of the general linear model.

Parameter B. S.E. t p 95% Confidence Interval
Lower Bound Upper Bound
Intercept −1.592 0.679 −2.344 0.020 −2.932 −0.252
Age 0.005 0.009 0.550 0.583 −0.013 0.024
Catastrophizing −0.210 0.082 −2.554 0.011 −0.373 −0.048
Depression 0.000 0.010 0.028 0.978 −0.020 0.021
Low tolerance 1.380 0.508 −2.717 0.007 0.378 2.382
Normal Tolerance (Ref) --
CBT −0.102 0.301 −0.339 0.735 −0.695 0.492
EDU −0.925 0.311 −2.979 0.003 −1.538 −0.313
EAET (Ref) --
Baseline BPI severity 0.492 0.073 6.784 0.000 0.349 0.635
Low tolerance*CBT −1.906 0.747 −2.550 0.012 −3.381 −0.431
Low Tolerance*EDU −0.400 0.641 −0.624 0.533 −1.665 0.865
Low Tolerance*EAET (Ref) --
Normal Tolerance*CBT (Ref) --
Normal Tolerance*EDU (Ref) --
Normal Tolerance*EAT (Ref) --
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Abbreviations: CBT = Cognitive Behavioral Therapy; EDU = Education; EAET = Emotional Awareness and Expression Therapy; BPI = Brief Pain Inventory

Figure 1.

Figure 1.

Open in a new tab

Estimated marginal means for clinical pain improvement by treatment assignment and pain tolerance group. Low Tolerance: EAET, n = 57; CBT, n = 51; FM Education, n = 46. Normal Tolerance: EAET, n = 11; CBT, n = 10; FM Education, n = 21

Abbreviations: EAET = Emotional Awareness and Expression Therapy; CBT = Cognitive Behavioral Therapy; EDU = Education

DISCUSSION

Our primary finding in this study is that normal experimental pressure pain tolerance in FM patients at baseline predicted substantial improvement in clinical pain severity following EAET, but not CBT or FM Education. These effects were not accounted for by covariates of pain tolerance, including baseline pain catastrophizing and depression. It is noteworthy that patients with normal pain tolerance in the EAET condition showed average estimated improvements of greater than 40%. Given IMMPACT recommendations that a 30% or greater improvement in pain is clinically significant, our findings demonstrate substantial clinical meaning for this subset of patients39. To our knowledge, this is the first study to use QST to predict response to psychological interventions in individuals with chronic pain.

Although QST has never been used to predict response to psychological treatment for pain, it has been used in several studies in an attempt to predict post-surgical analgesic use and analgesic efficacy in chronic pain. Although the QST methods used were heterogeneous, a majority of studies have shown that increased pain sensitivity at baseline predicts greater post-surgical analgesic use40. Furthermore, systematic reviews suggest that higher levels of preoperative pain sensitivity as measured by QST are associated with greater post-operative pain in a variety of conditions41, though it is worth noting that results have differed significantly across studies and paradigms. Some studies have also shown that measures of pain tolerance specifically can predict treatment response 15,42–44. Chronic pain patients who had lower pain tolerance were more likely to benefit from COX-2 inhibition 15,42. In another study, high ischemic pain tolerance in women, but not men, predicted larger increases in activity and reductions in clinical pain severity following a multi-component pain management program43. The current study provides preliminary evidence that the mechanistic differences measured by QST may include those on which psychological-based therapy appears to act.

Whereas CBT focuses on FM as a chronic disease requiring symptom management, EAET operates on the rationale that FM is exacerbated or maintained by unresolved stressful, traumatic, or conflictual emotional events5. In order to resolve these events, EAET seeks to create new corrective experiences and encourages patients to engage and embrace important emotions and interpersonal interactions5. This therapy, which can be emotionally and interpersonally challenging, was developed to be consistent with the “stress intolerance and pain hypersensitivity model” of FM45. Widespread hyperalgesia is a well-documented feature of FM and is thought to reflect the central neurobiological sensitization of the disorder1,30. Greater hyperalgesia and lower pain tolerance are closely linked with a host of psychosocial risk factors, including increased pain catastrophizing, depression, anxiety, post-traumatic stress symptoms, and problematic emotional regulation, including limited emotional awareness and expression45,46.

The current study echoes previous literature showing that patients with higher experimental pain tolerance report less catastrophic thinking about pain and less psychological distress47–50. Therefore, the current results may reflect the likelihood that patients with normal pain tolerance have more emotional stability and the cognitive/affective resources available to benefit from the intense emotional confrontation that is inherent to EAET. As Edwards et al.43 discussed of their finding that higher ischemic pain tolerance predicted better treatment outcomes for women, when challenging treatment procedures are uncomfortable, higher pain tolerance and better coping abilities may increase the likelihood of successful engagement in such procedures. In contrast, patients whose low pain tolerance reflects less emotional stability and limited coping resources may not be ready or able to successfully engage in EAET, at least as it was conducted in this clinical trial. Another possible explanation is that FM patients with normal pain sensitivity display an attitude of stoicism, defined as endurance of hardship without exhibiting emotion51. Previous literature has shown that individuals with chronic pain and stoic attitudes towards their pain are more likely to underreport their symptoms51–53. Such stoic or suppressive processes may contribute to the both higher pain tolerance and under-reporting of chronic pain symptoms as an outcome measure. It is possible that people who are stoic and who suppress both their emotional distress and pain may uniquely benefit from EAET, which encourages patients to directly confront and process unresolved stressful events. We acknowledge, however, that such explanations are speculative; these processes were not assessed in this trial and merit future research.

There are several limitations of the current study. Due to a limited number of male patients, only female patients were included. In addition, patients were predominantly white with higher educational attainment, so generalizability is limited. Future research should examine more diverse samples. Additionally, only one QST modality at a single body site was employed – the use of more varied methods may provide additional insight about the potential role of sensory mechanisms in predicting the efficacy of psychological therapy. Although the overall number of patients was fairly large for a treatment study of FM, the overall trial effects on pain severity were limited. Furthermore, the subgrouping of patients based on pressure pain sensitivity resulted in small numbers of participants in the normal tolerance groups. As this was a secondary analysis, no power analyses for these interaction effects were conducted. These results need to be replicated in a larger sample.

Currently, consistent and significant improvement in FM from any available intervention available is rare. In this trial, both active interventions benefited only a minority of patients 11, suggesting even more strongly the value of targeting treatments to patient characteristics. Many strategies focus on reducing key symptoms, increasing daily function, and improving mood; however, there has been inadequate effort to understand the features of FM patients who responds well to therapy. The current results, if replicated, may support a prognostic role for QST in phenotyping patients for psychotherapeutic interventions targeting chronic pain in FM. Furthermore, expanding these methods to other chronic pain conditions could provide insight on the relationship between different underlying pain mechanisms and response to psychotherapeutic interventions. However, generalization of the prognostic role of QST from FM to other pain conditions may be limited, given evidence that QST profiles differ between FM and chronic pain, for example (Blumenstiel et al.)54.

Acknowledgements

This research was funded by the National Institute of Arthritis, Musculoskeletal, and Skin Diseases, part of the National Institutes of Health, under award number AR057808. The content, including study design, data collection, data analysis, interpretation of data, writing of the report, and the decision to submit the report, is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Footnotes

Conflict of Interest Statement

S. E. Harte has received grants and personal fees from Aptinyx; he is also a co-inventor of the MAST device used in this study and a member of Arbor Medical Innovations, LLC, which licenses this device from the University of Michigan. D. J. Clauw has received personal fees from Abbott Pharmaceutical, Aptinyx, Astellas Pharmaceutical, Cerephex, Daiichi Sankyo, Pfizer, Samumed, Theravance, Tonix, Williams & Connolly LLP, and Zynerba and has received research support from Aptinyx, Cerephex, and Pfizer. D. A. Williams serves as a consultant to Community Health Focus Inc. He is past President of the American Pain Society. G. H. Kruger is also a co-inventor of the MAST system used in this study and founder of Arbor Medical Innovations, who is the current licensee of the MAST technology. The remaining authors have no conflict of interest to declare.

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