Affective pain modulation in fibromyalgia, somatoform pain disorder, back pain, and healthy controls

Examining the role of mood in pain-limited treadmill walking duration in young healthy individuals

PURPOSE

The purpose of the study was to examine the effects of acute mood modulation on treadmill walking duration during experimental pain application.

METHODS

This was a repeated measure, within-subject study design. 30 healthy individuals (Males: Females 16:14; age 22.9 ± 2.5 years; height 170.9 ± 9.5 cm; body mass 68.4 ± 14.6 kg) attended a familiarization session and three experimental sessions, whereby they simultaneously viewed emotionally evoking stimulus from the International Affective Picture System (IAPS) and performed two treadmill walking tests (maximum 10 min duration) with a fixed nociceptive input applied to the thigh (pressure cuff). The primary outcome was treadmill walking duration during pain application to achieve a fixed pain score. During walking, mood (Self-Assessment Manikin: SAM 0-9) and pain (numerical rating scale: NRS 0-10) were measured.

RESULTS

Mood valence scores were significantly different in all conditions (p < 0.001), negative (2.4 ± 0.3), neutral (4.9 ± 0.6) and positive (6.6 ± 0.3). There was a significant difference (p = 0.04) in the treadmill walking duration for different mood states. For the primary outcome, post hoc analysis found differences between the negative and positive mood conditions for the treadmill walking durations to reach pain scores of 3 (negative: 224 ± 49 s; positive: 259 ± 60s, effect size [ES]: 0.80), 4 (negative: 262 ± 59 s; positive: 326 ± 90s, ES: 0.92), 5 (negative: 313 ± 86 s; positive: 385 ± 113 s, ES: 0.90), 6 (negative: 367 ± 106 s; positive: 447 ± 113 s, ES: 1.04) and 7 (negative: 423 ± 114 s; positive: 521 ± 110 s, ES: 1.02). There was no significant difference in the treadmill walking duration between the neutral vs negative mood and neutral vs positive mood conditions.

CONCLUSION

These results highlight the potential psychophysiological impacts on the pain experience in healthy individuals and encourages pursuit in strategies to minimize pain-limited exercise, a highly prevalent issue in the chronic pain population.

SIGNIFICANCE

Walking-based rehabilitation, designed to improve physical activity, has been shown to improve pain and disability. However active participation and adherence in walking-based rehabilitation has shown to be jeopardized by pain and pain-related cognitive and behavioural adaptations. This study examined the effect of a shift in mood on pain perception and treadmill walking tolerance. We found that with a worse mood, individuals were less tolerant of pain and walked on the treadmill for a shorter duration. These results suggest that factors which improve mood should be combined with walking-based training to improve tolerance.

Heart Rate Variability, Autonomic Reactivity, and Emotion Regulation during Sadness Induction in Somatic Symptom Disorder

BACKGROUND

Preliminary evidence suggests altered heart rate variability (HRV) and impaired emotion regulation (ER) in somatic symptom disorder (SSD). Moreover, HRV can be considered an index of ER. Yet, to date, research on HRV and emotional reactivity in SSD is scarce and findings are inconsistent. Thus, this study aimed to examine ER differences, HRV at rest, and in response to emotion induction in persons with SSD compared to controls.

METHODS

The sample comprised 44 persons with SSD (DSM-5; 79.5% female, Mage = 45.7, SD = 14.7) and 41 persons without SSD (non-SSD; 78% female, Mage = 44.2, SD = 14.7). We assessed the participants' somatic symptom severity, ER, and control variables (e.g., depressive symptoms). Frequency and time domain HRV by ECG and subjective emotional states were measured at rest, under sadness induction, and during recovery periods. We evaluated baseline between-group differences with t-tests, and HRV and emotional reactivity and recovery with repeated measures ANOVAs.

RESULTS

We found no significant differences in resting state HRV between persons with and without SSD. Regarding reactivity and recovery, SSD group showed lower reactivity in SDNN (standard deviation of NN interval) than non-SSD group. Moreover, SSD group reported more maladaptive ER techniques (e.g. rumination) and a higher effort to regulate their emotions during the experiment than non-SSD group.

CONCLUSIONS

The study indicated impaired ER in persons with SSD. This finding showed more clearly in self-report than in HRV. Further research on HRV reactivity including tasks evoking other negative emotions in persons with SSD is required.

A randomized, placebo-controlled, double-blinded mechanistic clinical trial using endotoxin to evaluate the relationship between insomnia, inflammation, and affective disturbance on pain in older adults: A protocol for the sleep and Healthy Aging Research for pain (SHARE-P) study

Chronic pain is prevalent in older adults. Treatment, especially with opioids, is often ineffective and poses considerable negative consequences in this population. To improve treatment, it is important to understand why older adults are at a heightened risk for developing chronic pain. Insomnia is a major modifiable risk factor for chronic pain that is ubiquitous among older adults. Insomnia can also lead to heightened systemic inflammation and affective disturbance, both of which may further exacerbate pain conditions in older adults. Endotoxin exposure can be used as an experimental model of systemic inflammation and affective disturbance. The current study aims to understand how insomnia status and endotoxin-induced changes in inflammation and affect (increased negative affect and decreased positive affect) may interact to impact pain facilitatory and inhibitory processes in older adults. Longitudinal data will also assess how pain processing, affective, and inflammatory responses to endotoxin may predict the development of pain and/or depressive symptoms. The current study is a randomized, double-blinded, placebo-controlled, mechanistic clinical trial in men and women, with and without insomnia, aged 50 years and older. Participants were randomized to either 0.8ng/kg endotoxin injection or saline placebo injection. Daily diaries were used to collect variables related to sleep, mood, and pain at two-week intervals during baseline and 3-, 6-, 9-, and 12-months post-injection. Primary outcomes during the experimental phase include conditioned pain modulation, temporal summation, and affective pain modulation ∼5.5 hours after injection. Primary outcomes for longitudinal assessments are self-reported pain intensity and depressive symptoms. The current study uses endotoxin as an experimental model for pain. In doing so, it aims to extend the current literature by: (1) including older adults, (2) investigating insomnia as a potential risk factor for chronic pain, (3) evaluating the role of endotoxin-induced affective disturbances on pain sensitivity, and (4) assessing sex differences in endotoxin-induced hyperalgesia.

Clinicaltrialsgov

NCT03256760.

Trial sponsor

NIH R01AG057750-01.

Gamma Band Oscillations Reflect Sensory and Affective Dimensions of Pain

Pain is a multidimensional process, which can be modulated by emotions; however, the mechanisms underlying this modulation are unknown. We used pictures with different emotional valence (negative, positive, and neutral) as primes and applied electrical painful stimuli as targets to healthy participants. We assessed pain intensity and unpleasantness ratings and recorded electroencephalograms (EEGs). We found that pain unpleasantness and not pain intensity ratings were modulated by emotion, with increased ratings for negative and decreased ratings for positive pictures. We also found two consecutive gamma band oscillations (GBOs) related to pain processing from time frequency analyses of the EEG signals. The early GBO had a cortical distribution contralateral to the painful stimulus and its amplitude was positively correlated with intensity and unpleasantness ratings, but not with prime valence. The late GBO had a centroparietal distribution and its amplitude was larger for negative compared to neutral and positive pictures. The emotional modulation effect (negative vs. positive) of the late GBO amplitude was positively correlated with pain unpleasantness. The early GBO might reflect the overall pain perception, possibly involving the thalamocortical circuit, while the late GBO might be related to the affective dimension of pain and top-down-related processes.

Observing physicians acting with different levels of empathy modulates later assessed pain tolerance

OBJECTIVES

The patient-physician relationship is essential for treatment success. Previous studies demonstrated that physicians who behave empathic in their interaction with patients have a positive effect on health outcomes. In this study, we investigated if the mere perception of physicians as empathic/not empathic modulates pain despite an emotionally neutral interaction with the patients.

METHODS

N = 60 women took part in an experimental study that simulated a clinical interaction. In the paradigm, each participant watched two immersive 360° videos via a head-mounted display from a patient's perspective. The physicians in the videos behaved either empathic or not empathic towards a third person. Importantly, these physicians remained emotionally neutral in the subsequent virtual interaction with the participants. Finally, participants received a controlled, painful pressure stimulus within the narratives of the videos.

RESULTS

The physicians in the high compared with the low empathy videos were rated as more empathic and more likable, indicating successful experimental manipulation. In spite of later neutral behaviour of physicians, this short observation of physicians' behaviour towards a third person was sufficient to modulate pain tolerance of the participants.

CONCLUSIONS

The finding of this study that the mere observation of physicians' behaviour towards a third person modulates pain, despite a neutral direct interaction with the participants, has important clinical implications. Further, the proposed paradigm enables investigating aspects of patient-physician communication that are difficult to examine in a clinical setting.

Positive affect and distraction enhance while negative affect impairs pain modulation in recurrent low back pain patients and matched controls

ABSTRACT

Pathophysiological causes of low back pain (LBP) remain generally unclear, so focus has shifted to psychosocial features and central pain processing. Effects of attentional and affective manipulation on conditioned pain modulation (CPM) and tonic pain perception were examined in thirty recurrent LBP patients in two sessions, one with and one without clinical pain, and compared to healthy participants. Phasic cuff pressure on one leg, scored on a numerical rating scale (NRS), was used for test-stimuli (TS) and contralateral tonic cuff pain rated on an electronic visual analogue scale (eVAS) was the conditioning-stimulus (CS). TS were assessed before and during: 1) control with no manipulation/CS, 2) three attentional manipulations (Flanker with/without CS or CS-Only), and 3) three affective manipulations (positive, neutral, negative pictures) with CS. Greater inhibition of TS-NRS scores was observed in CS-only (P=0.028), combined CS&attention (P=0.026), and CS&Positive (P=0.006) than Control paradigms, and greater in CS&Positive (P=0.019) than CS&Negative paradigms. eVAS scores of CS pain increased throughout all paradigms with CS (P<0.05), except the CS&Positive paradigm, and greater facilitation was observed in the CS-Only paradigm than all others (P<0.02) and lower facilitation was additionally observed in the CS&Positive paradigm compared to CS&Attention and CS&Negative paradigms (P<0.01). Flanker effects and interruptive effects of CS pain on attention were observed consistent with prior findings, and affective manipulation produced less shift in valence among people with RLBP than controls (P<0.05). Attention and positive affect with CS pain evoked CPM, and all attentional/affective tasks, especially positive affect, reduced facilitation of CS pain.

Assessing Physical Pain Perception and Psychological Distress Tolerance through the MMPI-2-RF: A Comparison of Multimethod Measures

While transdiagnostic factors are important domains in clinical assessment and treatment, there is little research to link such constructs to widely accepted and utilized broadband assessments such as the Minnesota Multiphasic Personality Inventory, 2nd edition - Restructured Form (MMPI-2-RF). A handful of studies suggest the ability of the MMPI-2-RF scales to capture variance in transdiagnostic constructs; however, this literature relies solely on self-report criterion measures, despite evidence that self-report and behaviorally-indexed correlates of psychopathology may measure varied aspects of the intended construct and can often yield differing results. The current study investigated MMPI-2-RF scales' ability to assess two widely examined transdiagnostic constructs, distress tolerance and pain perception, across both self-report and behavioral indicators. The sample included 115 undergraduate students who completed a valid MMPI-2-RF and multimethod measures of pain perception and distress tolerance. The results aligned with prior research in areas of internalizing symptoms, psychopathy, and suicide risk factors in self-report, but not behaviorally-based, assessment. Implications of this inconsistency, the association between clinical assessment and transdiagnostic constructs, and the heterogeneity of the distress tolerance and pain perception constructs are discussed.

Influence of acute pain on valence rating of words

Numerous studies showed the effect of negative affective and pain-related semantic primes enhancing the perceived intensity of successive painful stimuli. It remains unclear whether and how painful primes are able to influence semantic stimuli in a similar way. Therefore, we investigated the effects of noxious primes on the perception of the valence of subsequent semantic stimuli. In two experiments, 48 healthy subjects were asked to give their valence ratings regarding different semantic stimuli (pain-related, negative, positive, and neutral adjectives) after they were primed with noxious electrical stimuli of moderate intensity. Experiment 1 focused on the existence of the effect, experiment 2 focused on the length of the effect. Valence ratings of pain-related, negative, and positive words (not neutral words) became more negative after a painful electrical prime was applied in contrast to no prime. This effect was more pronounced for pain-related words compared to negative, pain-unrelated words. Furthermore, the priming effect continued to affect the valence ratings even some minutes after the painful priming had stopped. So, painful primes are influencing the perception of semantic stimuli as well as semantic primes are influencing the perception of painful stimuli.

Medial Prefrontal Transcranial Direct Current Stimulation Aimed to Improve Affective and Attentional Modulation of Pain in Chronic Low Back Pain Patients

Chronic low back pain (CLBP) is often without clear underlying pathology. Affective disturbance and dysfunctional pain mechanisms, commonly observed in populations with CLBP, have, therefore, been suggested as potential contributors to CLBP development and maintenance. However, little consensus exists on how these features interact and if they can be targeted using non-invasive brain stimulation. In this pilot trial, 12 participants completed two phases (Active or Sham) of high-definition transcranial direct current stimulation (HD-tDCS) to the medial prefrontal cortex, applied for 20 min on three consecutive days. Clinical pain ratings, questionnaires, and sensitivity to painful cuff pressure were completed at baseline, then 4 trials of conditioned pain modulation (CPM; alone, with distraction using a Flanker task, with positive affect induction, and with negative affect induction using an image slideshow) were performed prior to HD-tDCS on Day 1 and Day 4 (24 h post-HD-tDCS). At baseline, attentional and affective manipulations were effective in inducing the desired state (p < 0.001) but did not significantly change the magnitude of CPM-effect. Active HD-tDCS was unable to significantly alter the magnitude of the shift in valence and arousal due to affective manipulations, nor did it alter the magnitude of CPM under any basal, attentional, or affective manipulation trial significantly on Day 4 compared to sham. The CPM-effect was greater across all manipulations on Day 1 than Day 4 (p < 0.02) but also showed poor reliability across days. Future work is needed to expand upon these findings and better understand how and if HD-tDCS can be used to enhance attentional and affective effects on pain modulation.

The relationship of cortical activity induced by pain stimulation with clinical and cognitive features of somatic symptom disorder: A controlled functional near infrared spectroscopy study

OBJECTIVE

The neurobiological correlates of Somatic Symptom Disorder (SSD) introduced in the DSM-5 has been the focus of a limited investigation. We aimed to examine the cortical response to painful stimuli and its relationship to symptom severity as well as cognitive and psychological characteristics in proposed models of somatoform disorders.

METHODS

We measured hemodynamic responses by 52-channel functional near-infrared spectroscopy. We compared the cortical response to painful stimuli in index patients with SSD (N = 21) versus age, and gender matched healthy control subjects (N = 21). We used brush stimulation as the control condition. We analyzed the relationship of cortical activity with SSD symptom severity as well as somatosensory amplification (SSA), alexithymia, dysfunctional illness behaviour, worry, and neuroticism.

RESULTS

Patients with SSD had higher somatic symptom severity, SSA, alexithymia, neuroticism, illness-related worry, and behaviour. Somatic symptom severity was predicted by a model including SSA and subjective feeling of pain in the index patients. Activity in the left-angular and right-middle temporal gyri was higher in the SSD subjects than the controls during pain stimulation. Positive correlations were detected between mean pain threshold levels and left middle occipital gyrus activity, as well as between SSA-scores and right-angular gyrus activity during pain condition in the index patients with SSD.

CONCLUSION

We present the first evidence that representation of pain in terms of cortical activity is different in subjects with SSD than healthy controls. SSA has functional neuroanatomic correlates and predicts symptom severity in SSD and therefore is involved as a valid intermediate phenotype in SSD pathophysiology.

Positive affect and chronic pain: a preregistered systematic review and meta-analysis

Chronic noncancer pain (CNCP) is a significant health burden among adults. Standard behavioral therapies typically focus on targeting negative affect (NA) and yield only modest treatment effects. The aims of this study were to systematically review and investigate the association between positive affect (PA) and pain severity among adults with CNCP. Databases that were searched included MEDLINE (PubMed), PsycINFO, CINAHL, ProQuest Dissertations and Theses, OLASTER, Open Grey, and PsyArXiv (inception to July 23, 2019). We analyzed studies that: (1) used observational, experimental, or intervention study designs; (2) enrolled individuals with CNCP (pain ≥ 12 weeks); and (3) reported full quantitative results on outcomes. Two researchers independently screened articles, extracted data, and assessed the risk of bias. The main meta-analysis was followed by subgroup analyses. All analyses were performed using random-effects models. Formal tests for heterogeneity (Q-statistic; I) and publication bias (p-curve and p-uniform*) were performed. We meta-analyzed 29 studies with 3521 participants. Results demonstrated that PA inversely impacts pain severity in people with CNCP (r = -0.23). Subgroup analyses showed a significant effect for gender and marginally significant effects for age in studies that adjusted for NA. On average, effect sizes for observational studies were larger in studies with a higher proportion of female respondents and in studies that did not adjust for NA. Finally, larger effect sizes were found in intervention studies with older compared with younger samples.

How words impact on pain

INTRODUCTION

The wording used before and during painful medical procedures might significantly affect the painfulness and discomfort of the procedures. Two theories might account for these effects: the motivational priming theory (Lang, 1995, American Psychologist, 50, 372) and the theory of neural networks (Hebb, 1949, The organization of behavior. New York, NY: Wiley; Pulvermuller, 1999, Behavioral and Brain Sciences, 22, 253; Pulvermüller and Fadiga, 2010, Nature Reviews Neuroscience, 11, 351).

METHODS

Using fMRI, we investigated how negative, pain-related, and neutral words that preceded the application of noxious stimuli as priming stimuli affect the cortical processing and pain ratings of following noxious stimuli.

RESULTS

Here, we show that both theories are applicable: Stronger pain and stronger activation were observed in several brain areas in response to noxious stimuli preceded by both, negative and pain-related words, respectively, as compared to preceding neutral words, thus supporting motivational priming theory. Furthermore, pain ratings and activation in somatosensory cortices, primary motor cortex, premotor cortex, thalamus, putamen, and precuneus were even stronger for preceding pain-related than for negative words supporting the theory of neural networks.

CONCLUSION

Our results explain the influence of wording on pain perception and might have important consequences for clinical work.

Calidad de vida, emociones negativas, autoeficacia y calidad del sueño en pacientes con dolor crónico: efectos de un programa de intervención psicológica

El dolor crónico es un problema de salud que afecta a entre el 10 y el 30% de la población. El objetivo del presente estudio consiste en evaluar la eficacia de un programa de intervención grupal en dolor crónico. Se realizó un estudio cuasi experimental. La muestra estuvo compuesta por 105 participantes de la Unidad de Dolor del Hospital General Universitario de Alicante. Se administró una batería de cuestionarios pre y post a la aplicación del programa. En el estudio se midió el nivel de dolor, la calidad de vida, ansiedad, depresión, atributos del sueño y autoeficacia. Se obtuvieron mejoras significativas en los niveles de ansiedad, depresión calidad de vida física, autoeficacia en todas sus dimensiones (control de síntomas, funcionamiento físico y control del dolor) y aspectos de los atributos del sueño, como cantidad y alteraciones del sueño. El programa protocolizado y realizado por profesionales entrenados es efectivo para disminuir la percepción del dolor, aumentar la calidad de vida en su componente físico, mejorar la autoeficacia y los atributos del sueño en pacientes con dolor crónico.

Negative affect as mediator between emotion regulation and medically unexplained symptoms

BACKGROUND

Research on emotion regulation (ER) in medically unexplained physical symptoms (MUS) is rare.

PURPOSE

The goal of this study was to compare ER skills between MUS-patients without comorbid depression, MUS-patients with comorbid depression (MUS+MDD), patients with major depressive disorder (MDD), and healthy controls. Additionally, we examined the mediating effect of depression and anxiety on the relationship between ER and somatization.

METHODS

The Emotion-Regulation Skills Questionnaire (ERSQ) and other self-report measures were completed by 138 MUS-patients, 114 MUS+MDD-patients, 106 MDD-patients, and 100 healthy controls. Multiple mediation analyses were applied to investigate the role of depression and anxiety as potential mediators.

RESULTS

A MANCOVA and post-hoc test with age, sex and education as covariates indicated that ER skills of the MUS-group were lower than the controls (p<0.001-p=0.047), but higher than the MDD- and MUS+MDD-group (p<0.001-p=0.042). ER skills of the MDD-group and MUS+MDD-group did not differ (p=0.78-p=0.99), but were lower than controls (p<0.001-p=0.011). In the MUS-groups depression and anxiety had a mediating effect on the relationship between ER and somatization (b=-0.23, 95% bias-corrected CI: -0.30, -0.17). The direct effect of ER on somatization was no longer significant when controlling for the mediating variables (b=0.07, p=0.083).

CONCLUSIONS

Our study reveals that patients with MUS+MDD have higher deficits in ER skills than MUS patients without MDD. Additionally, deficits in ER in MUS-patients are influenced by depression and anxiety. This indicates that MUS-patients with comorbid mental disorders might benefit from an emotion regulation training.

Prospective replication study implicates the catechol-O-methyltransferase Val158Met polymorphism as a biomarker for the response to morphine in patients with cancer

Genetic differences in humans cause clinical difficulties in opioid treatment. Previous studies indicate that a single nucleotide polymorphism in the catechol-O-methyltransferase (COMT) gene (rs4680; p.Val¹⁵⁸Met) may present as a predictive biomarker for the response to morphine treatment. In our previous pilot exploratory study, patients with a G/G genotype were demonstrated to require a higher dose of morphine, compared with patients with A/A and A/G genotypes. In the present study, the aim was to replicate the findings in an independent cohort of opioid-treatment-naïve patients exhibiting various types of cancer. This prospective study was conducted from 2011 to 2012 at the Kindai University Faculty of Medicine. A total of 50 patients with opioid-treatment naïve and histologically confirmed malignant neoplasms who were scheduled to undergo opioid treatment were evaluated in the present study. Assessments were conducted pre-treatment (day 1), post-treatment (day 1), and one week after treatment (day 8). The required dose of morphine on day 1 was significantly higher for patients with the G/G genotype of COMT, compared with those with the A/A and A/G genotypes (P=0.013). The results of the present study provide additional evidence that the COMT genotype may be a predictive biomarker for the response to morphine treatment.

Health care utilization in outpatients with somatoform disorders: Descriptives, interdiagnostic differences, and potential mediating factors

OBJECTIVE

Somatoform disorders are characterized by increased health care utilization producing high health costs. The aim of this study was to assess facets of and interdiagnostic differences in health care use in somatoform disorders and to examine health anxiety, symptom-related disability, depression, and phobic anxiety as potential mediating factors of the relationship between somatization and health care use.

METHOD

An outpatient sample of N=254 patients with somatoform disorders was investigated by analyzing different facets of their health care use over the last 12months. Multiple mediation analyses were applied.

RESULTS

Participants reported a mean of 28.02 doctor visits over the last year. Patients fulfilling criteria of DSM-IV somatization disorder had a significantly higher number of doctor visits than patients with undifferentiated somatoform, and somatoform pain disorder, all p≤.006. In most health care use variables, patients with comorbid mental disorders did not differ from patients without comorbidities. The mediation model on the effect of all mediator variables on the relationship between somatization and health care use reached significance (b=0.32, 95% CI: 0.0576, 0.6435). Surprisingly, specific mediator effects were found for health anxiety (b=0.06, 95% CI: 0.0004, 0.1505) and disability (b=0.18, 95% CI: 0.0389, 0.3530), but not for depression and phobic anxiety.

CONCLUSIONS

Health anxiety and symptom-related disability should be further considered when investigating potential etiological factors of increased health care use.

TMD and chronic pain: a current view

This review aims at presenting a current view on the physiopathologic mechanisms associated with temporomandibular disorders (TMDs). While joint pain is characterized by a well-defined inflammatory process mediated by tumor necrosis factor-α and interleukin, chronic muscle pain presents with enigmatic physiopathologic mechanisms, being considered a functional pain syndrome similar to fibromyalgia, irritable bowel syndrome, interstitial cystitis and chronic fatigue syndrome. Central sensitization is the common factor unifying these conditions, and may be influenced by the autonomic nervous system and genetic polymorphisms. Thus, TMDs symptoms should be understood as a complex response which might get worse or improve depending on an individual's adaptation.

Affective Modulation of Brain and Autonomic Responses in Patients With Fibromyalgia

OBJECTIVES

Emotional dysregulation and abnormal processing of affective information are thought to play a significant role for the maintenance of pain in fibromyalgia. The motivational priming hypothesis states that negative emotions could increase pain via activation of the aversive system, thus leading to an affective modulation of defensive reflexes. Nevertheless, little is known about peripheral and central correlates of affective reflex modulation in fibromyalgia.

METHODS

Thirty patients with fibromyalgia and 30 healthy individuals were asked to view three video clips from a self-perspective to induce specific mood states. Video clips consisted of the same virtual walk through different locations of a park under three affective environments (unpleasant, pleasant, and neutral). Startle eyeblink reflex and heart rate response elicited by abrupt startle noises, as well as heart rate variability and electroencephalography (EEG) oscillations were recorded when participants were passively viewing the virtual environments.

RESULTS

Patients with fibromyalgia rated all environments as more negative and arousing than did healthy controls (p values < .05). Nevertheless, startle eyeblink reflex and heart rate response were lower in patients with fibromyalgia than in healthy controls when viewing all three environments (p values < .05). Patients with fibromyalgia also displayed lower heart rate variability, as well as higher EEG power (2-22 Hz) during all environments than did healthy controls (p values < .05).

CONCLUSIONS

Patients with fibromyalgia were characterized by relevant deficits in affective modulation of startle and cardiac responses, heart rate variability, and EEG power spectra in response to sustained induction of affective states. These findings suggest an alteration of emotional and attentional aspects of information processing at subjective, autonomic, and central nervous system levels.

The role of positive affect in pain and its treatment

OBJECTIVE

This narrative review summarizes and integrates the available literature on positive affect (PA) and pain to: (1) provide a brief overview of PA and summarize the key findings that have emerged in the study of PA and pain; (2) provide a theoretical foundation from which to understand how PA operates in the context of chronic pain (CP); and (3) highlight how the prevailing psychosocial treatments for CP address PA in the therapeutic context, and offer suggestions for how future treatment development research can maximize the benefit of PA for patients with CP.

RESULTS

In experimental studies, the evidence suggests PA is analgesic. In clinical studies, the association of PA and pain is dynamic, time variant, and may be best considered in context of its interacting role with negative affect.

DISCUSSION

We offer an "upward spiral" model of PA, resilience and pain self-management, which makes specific predictions that PA will buffer maladaptive cognitive and affective responses to pain, and promote active engagement in valued goals that enhance CP self-management.

The common link between functional somatic syndromes may be central sensitisation

OBJECTIVES

Functional somatic syndromes are common and disabling conditions that all include chronic pain, and which may be related to central nervous system sensitisation. Here, we address the concept of central sensitisation as a physiological basis for the functional somatic syndromes.

METHODS

A narrative review of the current literature on central sensitisation and physiological studies in the functional somatic syndromes.

RESULTS

Central sensitisation may be a common neurophysiological process that is able to explain non-painful as well as painful symptoms in these disorders. Furthermore, central sensitisation may represent an endophenotypic vulnerability to the development of these syndromes that potentially explains why they cluster together.

CONCLUSIONS

Further research is needed to verify these findings, including prospective studies and the standardisation of combined methods of investigation in the study of central sensitisation in functional somatic syndromes. In turn, this may lead to new explanatory mechanisms and treatments being evaluated. Our conclusions add to the debate over the nomenclature of these syndromes but importantly also provide an explanation for our patients.

Pain-related and negative semantic priming enhances perceived pain intensity

BACKGROUND

Negative affective and pain-related cues, such as pictures or words, have been shown to act as primes and enhance the perceived intensity of subsequent painful events. For pain-related semantic primes, it remains unclear whether this effect depends on negative valence itself or, specifically, on the pain-relatedness of the words.

OBJECTIVES

To investigate the effect of pain-related, negative affective (pain-unrelated) and neutral semantic primes on the perception of subsequent noxious target stimuli.

METHODS

Pain ratings in response to noxious electrical stimulation of light and moderate intensity were examined in 39 healthy subjects after subjects were exposed to semantic primes of different meaning and valence (pain-related, negative, positive and neutral adjectives) presented with different interstimulus intervals (0 ms, 500 ms and 1500 ms).

RESULTS

Increased pain ratings of noxious stimuli were observed following pain-related and negative compared with neutral primes.

DISCUSSION

The results support the motivational priming theory for semantic stimuli, indicating that affectively negative semantic primes increase subjective pain intensity. However, a specific pain-related priming effect was not reliably demonstrated. Additionally, it is shown that experimental parameters (ie, stimulus intensity and interstimulus interval) modify the extent of negative and pain-related semantic priming.

CONCLUSIONS

Verbal priming plays a role for the perception of noxious stimuli in a time-dependent manner.

Recognition of facially expressed emotions in patients with fibromyalgia syndrome

The study investigated the ability to identify facially expressed emotions in fibromyalgia syndrome (FMS) and its association with clinical parameters. Thirty-five FMS patients and 35 healthy controls accomplished a face recognition task. Additionally, pain severity, alexithymia, depression, anxiety, psychiatric co-morbidity and medication use were assessed. The patients displayed reduced task performance in terms of more misclassifications of emotional expressions than controls. Pain severity, alexithymia, depression and anxiety were inversely related to recognition performance, with pain severity accounting for the largest portion of test score variance. Psychiatric co-morbidity and medication had no impact on performance. The study documented impaired emotion recognition in FMS, which may contribute to the interpersonal difficulties and reduced social functioning related to this condition. As potential mechanisms mediating the occurrence of the deficits, altered affective processing due to interoceptive impairment as well as interference of central nervous nociceptive activity with cognitive and emotional processing are discussed.

Personality does not distinguish people with fibromyalgia but identifies subgroups of patients

OBJECTIVES

The objectives were to compare the personality of fibromyalgia (FM) patients with other chronic painful and nonpainful disorders considering the confusion due to psychopathology and to assess the clustering of FM patients according to their personality profile.

METHODS

Differences in the NEO Five-Factor Inventory between FM, non-FM chronic pain and drug-resistant epileptic patients were assessed including the confounding effect of demographics and psychopathological status by multivariate regression analysis. Clustering of FM patients was assessed by two-step cluster analysis. Differences in clinical severity and psychosocial problems between subgroups and their outcome 6 months after multidisciplinary treatment were assessed.

RESULTS

The final sample comprised 874 patients. Once the effect of confounding variables was considered, clinically nonsignificant differences in personality were observed between groups. FM patients could, however, be grouped into two clusters. Cluster 1 was characterized by higher neuroticism and lower extraversion and showed a worse pretreatment clinical state including more psychosocial problems. In spite of having reached a wider general improvement at 6-month follow-up, Cluster 1 patients remained more anxious and depressed.

CONCLUSIONS

Identifying personality-based subgroups of FM might allow implementing specific preventive strategies. FM treatment might be optimized by increasing medication compliance, improving therapeutic alliance and testing different therapeutic options and treatment sequencing for each personality subgroup.

Deficient modulation of pain by a positive emotional context in fibromyalgia patients

This study aimed to investigate the modulating effects of emotional context on pain perception in 16 patients with fibromyalgia syndrome (FMS) and 16 healthy control (HC) subjects. An infrared laser was used to apply individually adapted painful stimuli to the dorsum of the left hand. The emotional background of the painful stimuli was modulated by concurrent presentations of negative, neutral, and positive picture stimuli selected from the International Affective Picture System. As control conditions, painful stimuli and the pictures were also presented by themselves. During each of the 5 laser-picture trials, subjects received 10 painful stimuli and were asked to rate the average intensity and unpleasantness of the experienced pain. Functional magnetic resonance images were obtained, using a T2(∗) sensitive echo planar sequence. HC subjects showed a linear increase in pain intensity and unpleasantness ratings when painful stimuli were presented during positive, neutral, and negative pictures. In contrast, FMS patients showed a quadratic trend for pain intensity ratings indicating a lack of pain reduction by the positive pictures. In addition, the FMS patients showed less activation in secondary somatosensory cortex, insula, orbitofrontal cortex, and anterior cingulate cortex during the positive picture pain trials. Our results suggest that fibromyalgia patients are less efficient in modulating pain by positive affect and may benefit less from appetitive events than healthy control subjects.

Cognitive and emotional control of pain and its disruption in chronic pain

Chronic pain is one of the most prevalent health problems in our modern world, with millions of people debilitated by conditions such as back pain, headache and arthritis. To address this growing problem, many people are turning to mind-body therapies, including meditation, yoga and cognitive behavioural therapy. This article will review the neural mechanisms underlying the modulation of pain by cognitive and emotional states - important components of mind-body therapies. It will also examine the accumulating evidence that chronic pain itself alters brain circuitry, including that involved in endogenous pain control, suggesting that controlling pain becomes increasingly difficult as pain becomes chronic.

Efficacy of a Character Strengths and Gratitude Intervention for People with Chronic Back Pain

This study investigated the efficacy of a character strengths and gratitude intervention to reduce pain in people with chronic back pain. Eight participants (males = 4, females = 4) took part in a cross-over multi-baseline study over 5‒7 weeks. Comparisons were made for intervention efficacy effects by contrasting a character strengths approach with a comparison condition premised on positive memories. Daily measures were used to assess mood (happiness, sadness, anger) and pain. In addition, measures of happiness, depression, anxiety, pain catastrophising and pain were collected at each phase. The results indicated improved daily happiness and significantly reduced daily anger following the character strengths and gratitude intervention. This provides preliminary evidence that daily focusing on positive aspects of one's emotional experience benefits those with chronic back pain.

Cerebral blood flow dynamics during pain processing in patients with fibromyalgia syndrome

OBJECTIVES

Increased cerebral blood flow during processing of acute pain has repeatedly been observed in fibromyalgia syndrome. The study investigated the time dynamics of the pain-related hemodynamic response in fibromyalgia using transcranial Doppler sonography.

METHODS

In 25 women with fibromyalgia and 25 healthy participants, blood flow velocities in the anterior and middle cerebral arteries of both hemispheres were recorded, while heat stimuli of 45°C were applied to their forearms. Thermal pain threshold and subjective pain experience during stimulation were assessed, and the participants completed the McGill Pain Inventory, Beck Depression Inventory, and State-Trait Anxiety Inventory.

RESULTS

The early component of the blood flow response in both anterior cerebral arteries, that is, the steep flow increase during the initial stimulation period, was more pronounced in the patients than in the controls (mean [standard deviation] = 1.28% [1.85%] versus 0.24% [1.58%], p = .04). The patients showed lower pain threshold (p = .018), stronger sensory and affective pain experience (p < .001), and increased values on all questionnaire scales (all p values < .001). Although higher scores on each of the scales were associated with a stronger early blood flow response (r values ranging from 0.17 to 0.36), clinical pain severity proved to be the best predictor (β = .33, p = .02).

CONCLUSIONS

The increased blood flow response in the anterior cerebral arteries reflects hyperactivity of medial structures of the neuromatrix of nociception, structures involved in the processing of affective and cognitive aspects of pain. Aberrances in cerebral blood flow related to fibromyalgia and its clinical characteristics become particularly apparent in the enhancement of the initial component of the hemodynamic response.

Tonic pain grabs attention, but leaves the processing of facial expressions intact-evidence from event-related brain potentials

Emotion and attention are key players in the modulation of pain perception. However, much less is known about the reverse influence of pain on attentional and especially emotional processes. To this end, we employed painful vs. non-painful pressure stimulation to examine effects on the processing of simultaneously presented facial expressions (fearful, neutral, happy). Continuous EEG was recorded and participants had to rate each facial expression with regard to valence and arousal. Painful stimulation attenuated visual processing in general, as reduced P100 and late positive potential (LPP) amplitudes revealed, but did not interfere with structural encoding of faces (N170). In addition, early perceptual discrimination and sustained preferential processing of emotional facial expressions as well as affective ratings were not influenced by pain. Thus, tonic pain demonstrates strong attention-demanding properties, but this does not interfere with concurrently ongoing emotion discrimination processes. These effects point at partially independent effects of pain on emotion and attention, respectively.

Central pain mechanisms in chronic pain states--maybe it is all in their head

Mechanisms underlying chronic pain differ from those underlying acute pain. In chronic pain states, central nervous system (CNS) factors appear to play particularly prominent roles. In the absence of anatomical causes of persistent pain, medical sub-specialities have historically applied wide-ranging labels (e.g., fibromyalgia (FM), irritable bowel syndrome, interstitial cystitis and somatisation) for what now is emerging as a single common set of CNS processes. The hallmark of these 'centrally driven' pain conditions is a diffuse hyperalgesic state identifiable using experimental sensory testing, and corroborated by functional neuroimaging. The characteristic symptoms of these central pain conditions include multifocal pain, fatigue, insomnia, memory difficulties and a higher rate of co-morbid mood disorders. In contrast to acute and peripheral pain states that are responsive to non-steroidal anti-inflammatory drugs (NSAIDs) and opioids, central pain conditions respond best to CNS neuromodulating agents, such as serotonin-norepinephrine reuptake inhibitors (SNRIs) and anticonvulsants.

Blunted autonomic reactivity and increased pain tolerance in somatoform patients

Somatoform disorders are characterized by the presence of multiple somatic symptoms. Patients often experience different pain syndromes, and recent research suggests that sympathovagal balance is disturbed in somatoform patients, which could be related to alteration in pain sensitivity. This study analyzed how proposed sympathovagal imbalance interacts with objective pain assessment and the imagination of pain in somatoform disorders. Twenty-one patients (4 men) with diagnosed multisomatoform disorder were included in the study and matched to healthy control subjects. Autonomic measures and heart rate variability were assessed during baseline; pain perception was assessed by means of a pressure algometer and pain imagination. We found evidence for a sympathovagal imbalance in somatoform disorders characterized by low parasympathetic activation and high sympathetic activation during all conditions. Additionally, somatoform patients had reduced pain tolerance. Vagal withdrawal during pain assessment was more pronounced for healthy control subjects and correlated positively with assessed pain tolerance. During imagination somatoform, patients reported higher pain unpleasantness and higher pain intensity as compared to control subjects. We conclude that our data demonstrate an imbalance in sympathovagal activation and a hyposensitivity to pain tolerance stimuli in somatoform disorders. Parasympathetic reactivity might form crucial information when judging pain-associated affective-motivational components. Our results might be attributable to a deficient detection of visceral signals and might be a pathogenetic mechanism for the development of emotional difficulties and increased everyday vulnerability in somatoform patients.

Modulation of nociceptive and acoustic startle responses to an unpredictable threat in men and women

The present study examined whether a moderately aversive abdominal threat would lead to greater enhancement in affect- and pain-related defensive responding as indexed by the acoustic startle reflex (ASR) and nociceptive flexion reflex (NFR) in women compared to men. We also predicted sex differences in threat-related autonomic arousal measured by skin conductance responses (SCRs) to acoustic startle and noxious sural nerve stimulation. Unpredictable threat was manipulated by alternating 30-second safe ("no abdominal stimulation will be given") and threat ("abdominal stimulation may occur at anytime") periods. The experiment consisted of 2 blocks, each containing 4 safe and 4 threat periods in which the ASR or NFR was randomly probed 9-21 seconds following period onset. Unpredictable abdominal threat potentiated both ASR and NFR responses compared to periods signaling safety. SCRs to acoustic startle probes and noxious sural nerve stimulation were also significantly elevated during the threat vs safe periods. No sex differences in ASR or startle-evoked SCRs emerged. However, nociceptive responding was moderated by sex; females showed significant increases in NFR magnitudes across both safe and threat periods compared to males. Females also showed greater threat-potentiated SCRs to sural nerve stimulation than males. Our findings indicate that both affect- and pain-related defense and arousal systems are strongly influenced by threat of an aversive, unpredictable event, a situation associated with anticipatory anxiety. Females, compared to males, showed greater nociceptive responding and pain modulation when exposed to an unpredictable threatening context, whereas affect-driven ASR responses showed no such sex differentiation.

The Symptom Checklist-Revised (SCL-90-R) is able to discriminate between simulation and fibromyalgia

This study assessed the ability of the Symptom Checklist-Revised (SCL-90-R) to discriminate between two groups of fibromyalgia patients (those who were about to begin a treatment including the explicit aim of returning to work and those who were initiating a legal procedure to obtain permanent disability compensation) and two groups of healthy volunteers (medical students and psychology graduates), who were asked to produce a symptomatic resemblance to a chronic pain disorder. Logistic regression analyses were applied to the SCL-90-R subscales and individual probabilistic indices of simulation were calculated. Results showed that the SCL-90-R was able to discriminate between healthy subjects and both groups of patients with a high sensitivity and specificity. The individual indices of simulation, which might be more useful in clinical practice than the comparison of the SCL-90-R profiles, also showed an appropriate level of accuracy.

Experimental assessment of affective processing in fibromyalgia

Fibromyalgia syndrome (FMS) is a chronic pain disorder associated with widespread musculoskeletal pain, tenderness, and fatigue. Additionally, correlational research suggests negative affect (eg, depression, anxiety) and deficits in positive affect may contribute to FMS symptomatology. However, well-controlled, experimental research is necessary to ascertain whether patients with FMS have problems in affective processing. The present study used a well-validated picture-viewing paradigm to evoke emotional responses in 17 patients with FMS and 17 sex- and age-matched healthy control participants. Each participant viewed pleasant (erotica), neutral, and unpleasant (attack related) pictures, and abrupt white noises were delivered during two-thirds of the pictures to evoke startle eyeblinks. Appetitive and defensive responding was assessed from subjective (valence/pleasure and arousal ratings) and physiological (corrugator EMG, heart rate, skin-conductance response, startle-reflex modulation) reactions to pictures. Results suggested FMS was associated with greater defensive activation (displeasure, subjective arousal, corrugator EMG) to the unpleasant, threat-related pictures, but not deficits in appetitive activation to erotic pictures. Although preliminary, these data suggest individuals with FMS have deficits in affective processing, but this dysregulation may be limited to defensive activation. Implications for treatment and future research are discussed.

PERSPECTIVE

Fibromyalgia is a debilitating disease associated with affective distress. Results from the present study suggest that FMS is associated with enhanced defensive activation to nonpainful threat-related stimuli, but not deficits in appetitive reactions to erotic stimuli. These findings have implications for the treatment and study of FMS.

Current evidence for a modulation of low back pain by human genetic variants

The manifestation of chronic back pain depends on structural, psychosocial, occupational and genetic influences. Heritability estimates for back pain range from 30% to 45%. Genetic influences are caused by genes affecting intervertebral disc degeneration or the immune response and genes involved in pain perception, signalling and psychological processing. This inter-individual variability which is partly due to genetic differences would require an individualized pain management to prevent the transition from acute to chronic back pain or improve the outcome. The genetic profile may help to define patients at high risk for chronic pain. We summarize genetic factors that (i) impact on intervertebral disc stability, namely Collagen IX, COL9A3, COL11A1, COL11A2, COL1A1, aggrecan (AGAN), cartilage intermediate layer protein, vitamin D receptor, metalloproteinsase-3 (MMP3), MMP9, and thrombospondin-2, (ii) modify inflammation, namely interleukin-1 (IL-1) locus genes and IL-6 and (iii) and pain signalling namely guanine triphosphate (GTP) cyclohydrolase 1, catechol-O-methyltransferase, mu opioid receptor (OPMR1), melanocortin 1 receptor (MC1R), transient receptor potential channel A1 and fatty acid amide hydrolase and analgesic drug metabolism (cytochrome P450 [CYP]2D6, CYP2C9).