Neurophysiological and Psychosocial Mechanisms of Fibromyalgia: A Comprehensive Review and Call for An Integrative Model

The impact of obsessive beliefs on fibromyalgia: The mediating role of emotional dysfunction and obsessive-compulsive symptoms

BACKGROUND

The role of obsessive beliefs in the development and maintenance of Fibromyalgia syndrome (FMS) remains unclear. This study aims to compare patients with FMS and controls in terms of obsessive beliefs, quality of life, and comorbid psychiatric symptoms. In addition, this study uses structural equation modelling (SEM) to examine whether obsessive beliefs influence FMS symptom severity directly or through mediating factors.

METHOD

This study was conducted at Uşak Training and Research Hospital, Turkey, involving 116 adults, including 76 FMS patients (mean age = 43.2) and 40 controls (mean age = 45.8). Both groups completed the Short Form 12 Health Survey (SF-12), Obsessive Beliefs Questionnaire (OBQ) and Symptom Checklist-90 Revised (SCL-90-R), with the FMS group additionally completing the Fibromyalgia Impact Questionnaire (FIQ). SEM was applied to examine the direct and indirect effects of obsessive beliefs on FMS symptom severity.

RESULTS

In the FMS group, SF-12 subscale scores were lower, while OBQ-44 and SCL-90-R subscale scores (except for anger-hostility, phobic anxiety, and paranoid ideation) were higher compared to controls (all p < .05). The final model showed that the OBQ-Total Score negatively predicted SF-12 Role Emotional (β = -0.22, p = .042) and positively predicted SCL-90 Obsessive-Compulsive (β = 0.25, p = .013). SF-12 Role Emotional negatively predicted both the FIQ (β = -0.50, p < .001) and SCL-90 Obsessive-Compulsive (β = -0.40, p = .001), while SCL-90 Obsessive-Compulsive positively predicted the FIQ (β = 0.39, p = .002).

CONCLUSIONS

Our findings highlight the role of obsessive beliefs and emotional dysfunction in FMS severity, suggesting that targeting these factors may help alleviate symptoms. Future research should examine targeted therapies to enhance emotional regulation and cognitive flexibility in FMS.

Discounting seems the most toxic dimension of invalidation in fibromyalgia: a cross-sectional analysis

Invalidation, both discounting (overt negative social responses) and lack of understanding (absence of positive social responses), is a common problem in fibromyalgia. The 'Fibromyalgia Imbalance of Threat and Soothing Systems' (FITSS) model indicates that different neuropsychological processes may underlie these two components of invalidation. Guided by this model, the aim of the current study was to clarify the differentiation between these two components of invalidation by examining their association with fibromyalgia severity, anxiety, and depression. This cross-sectional study included the Illness Invalidation Inventory (3*I), the Fibromyalgia Impact Questionnaire (FIQ), and the Hospital and Depression Scale (HADS). Demographics of the 280 respondents with fibromyalgia were: mean age 42.6 ± 11.8 yrs., 95% female, mean FIQ score 59.1 ± 15,5, possible or probable cases of anxiety and depression, 49% and 42%, respectively. Regression analyses revealed that discounting was associated with severity of fibromyalgia (t = 4.10, β = 0.34, p <.001), anxiety (t = 3.50, β = 0.29, p <.001) and depression (t = 3.64, β = 0.30, p <.001) symptoms. Neither lack of understanding (-1.62 ≤ t ≤.10, -0.13 ≤ β ≤ 0.01, p ≥ 0.11) nor the interaction of discounting and lack of understanding (-0.19 ≤ t ≤ 1.10, -0.01 ≤ β ≤ 0.07, p ≥ 0.27) was related to any of the outcome variables. The total model accounted for 8.8%, 5.3%, and 8.3% (adjusted R2) of variance in fibromyalgia severity, anxiety, and depression, respectively. In relation to both mental and physical health, discounting seems the most toxic dimension of invalidation in fibromyalgia. This suggests that overt negative responses should get attention in its management, especially in more severe fibromyalgia. Both people with fibromyalgia and people in their environment have a role in reducing invalidation.

Exploring the role of shame and self-compassion on the link between fibromyalgia symptoms and depression: Insights from mediation and moderation analyses

The intricacies of the fibromyalgia-depression link accentuate the need to further explore underlying psychosocial mechanisms. External shame resulting from fibromyalgia's nature and associated impairment may increase the risk for depression. We explored whether being supportive and compassionate toward one's perceived shortcomings would potentially weaken this association. This cross-sectional study comprised 138 women with fibromyalgia. Participants were recruited via patient associations and invited to complete an online survey. Descriptive, correlational, mediation and moderation analyses were performed to test the driving hypotheses. Both mediation and moderation analyses accounted for approximately 40% of the variance in depressive symptoms. Fibromyalgia severity was directly and indirectly- through external shame- associated with depressive symptoms. The shame-depressive symptoms link was weaker in participants with greater self-compassion skills. Findings point to the importance of shame and self-compassion and the need to address them in research and clinical contexts.

The effect of the EXOPULSE Mollii Suit on pain and fibromyalgia-related symptoms-A randomized sham-controlled crossover trial

BACKGROUND

Fibromyalgia pain and related symptoms are poorly managed by approved pharmacological and alternative interventions. This trial aimed to evaluate the effects of the EXOPULSE Mollii Suit-a multisite transcutaneous electrical nerve stimulation device-on fibromyalgia pain, fatigue, affective symptoms, disease impact, and quality of life.

METHODS

Adult patients with fibromyalgia were enrolled. Phase 1 implied a randomized, sham-controlled, cross-over, double-blind trial, applying daily 1 h sessions of active or sham intervention, over 2 weeks (2-week washout). In the open-label phase 2, all patients received daily active intervention for 4 weeks. Comparisons on pain, fatigue, disease impact, affective symptoms, quality of life, clinical impression, and comfort ratings were performed using Friedman, Wilcoxon signed rank, and Chi2 tests.

RESULTS

Thirty-three patients completed the study (93.9% female, mean age: 51.3 years). Pain (primary endpoint assessed via a visual analog scale) was significantly reduced after the active (pre-active: 6.9 ± 1.4, post-active: 5.9 ± 1.8, pre-sham: 6.8 ± 1.4, post-sham: 6.6 ± 1.5) versus the sham intervention (X2 = 10.60, p = 0.014). This was also the case of other secondary endpoints (i.e., fatigue, anxiety, and disease impact), except depression and quality of life. The Clinical Global Impression of Change (CGI-C) was significantly different between the active and sham intervention periods (X2 p = 0.035), and the different proportions of categories were as follows: 'worsening' (sham: 18.2% vs. active: 0.0%), 'improvement' (sham: 48.5% vs. active 63.6%) or 'no change (sham: 33.3% vs. active 36.4%) respectively. After phase 2, significant positive effects were observed for most of the outcomes, and 78.8% of patients reported improvement according to CGI-C.

CONCLUSIONS

This study suggests the clinical benefits of the EXOPULSE Mollii Suit in alleviating pain and fibromyalgia-related fatigue, emotional symptoms, and disease impact. It is worth noting that the study has several limitations related to the low number of participants, the short-term analysis of effects in the first blinded and controlled phase, and the open-label nature of phase 2. Future studies with a larger cohort and longer protocol treatment are needed, to further confirm the current results, and evaluate the long-term effects of this technique.

SIGNIFICANCE

Patients with fibromyalgia suffer from pain as well as fatigue, sleep impairment, emotional disturbances, and altered quality of life. Transcutaneous electrical nerve stimulation might help manage those symptoms, but the available systems are limited by the fact that they could be applied at best over two sites. This randomized controlled study is the first to apply a multi-site transcutaneous electrical nerve stimulation device, the EXOPULSE Mollii Suit, with significant effects on fibromyalgia pain and related symptoms.

Differences in Plasma BDNF Levels Between Chronic Primary Musculoskeletal Pain, Fibromyalgia Syndrome, and Asymptomatic Subjects: A Cross-Sectional Study

This cross-sectional study compared plasma brain-derived neurotrophic factor (BDNF) levels among chronic primary musculoskeletal pain patients, chronic widespread pain patients, and asymptomatic controls. The study included 126 participants aged 18-65, divided into three groups of 42 each. Pain intensity was assessed using a Numeric Rating Scale (NRS), and plasma BDNF levels were measured via ELISA. Differences between groups were evaluated using ANOVA with 2000 bootstrap resamples and a bias-corrected and accelerated method. Results showed significantly higher plasma BDNF levels in chronic widespread pain patients (mean difference [MD] = 0.44; 95% CI = 0.28, 0.62; p < .001) compared to controls, and higher than in chronic primary musculoskeletal pain patients (MD = 0.83; 95% CI = 0.64, 1.02; p < .001). Chronic primary musculoskeletal pain patients had lower plasma BDNF levels compared to controls (MD = -0.39; 95% CI = -0.54, -0.24; p < .001). No significant correlations were observed between plasma BDNF levels and clinical variables. These findings suggest the potential of BDNF as a biomarker to differentiate chronic primary pain conditions.

Targeted delivery of a selenium-sulfa compound via cationic starch microparticles: Modulation of oxidative stress and pain pathways in fibromyalgia-like symptoms in mice

Cationic starch microparticles (CStMPs) loaded with 4-amino-3 -(phenylselenyl)benzenesulfonamide (4-APSB) were prepared and investigated in a model of fibromyalgia (FM) induced by intermittent cold stress (ICS) in male and female Swiss mice. The CStMPs/4-APSB were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, zeta potential, and particle size measurements, providing information about their chemical composition, surface charge, morphology/microstructure, and size (1.50 ± 0.5 μm). Following ICS exposure, the animals were treated with free 4-APSB (1 mg/kg), CStMPs/4-APSB (containing 0.13 mg of 4-APSB per mg of microparticles), or CStMPs, from days 5 to 10. The results revealed the successful incorporation of 4-APBS in the CStMPs. Free 4-APSB and CStMPs/4-APSB reversed nociceptive- and depressive-related behaviors in male and female mice exposed to ICS, attenuating the hallmark symptoms of FM. Those treatments (free 4-APSB and CStMPs/4-APSB) normalized the monoamine oxidase (MAO)-A activity in the cerebral cortex and the oxidative damage, providing the correct functioning of the enzyme Ca2+ -ATPase in the cerebral cortex and hippocampus of mice exposed to ICS. The CStMPs/4-APSB modulated the oxidative stress markers, specifically in the spinal cord of mice - an anatomical region intricately linked to pain pathways.

The effect of fibromyalgia syndrome on female patients diagnosed with chronic migraine

OBJECTIVE

To compare pain, quality of life, sleep, anxiety and depression, central sensitization, and functionality between chronic migraine (CM) patients with comorbid fibromyalgia syndrome (FMS) and patients with CM alone.

METHOD

Thirty three female patients with CM and thirty three female patients with CM+FMS were enrolled in the study. Demographic and clinical characteristics of the patients were recorded. FM was diagnosed based on the 2016 American College of Rheumatology diagnostic criteria. All participants were evaluated with Allodynia Symptom Checklist, Short Form-36 (SF-36), Pittsburgh Sleep Quality Index (PSQI), Hospital Anxiety and Depression Scale (HADS), Migraine Disability Assessment (MIDAS) and Headache Impact Test (HIT-6) questionnaires, and Central Sensitization Inventory (CSI). FM patients were also evaluated with Fibromyalgia Impact Questionnaire (FIQ).

RESULTS

The average number of headache days was significantly higher in patients with CM+FMS (p = 0.006). Among migraine accompanying symptoms, the number of patients with phonophobia was significantly higher in patients with CM+FMS (p = 0.008). While CSI score was 39.0 ± 11.7 in CM patients, it was 52.2 ± 9.2 in CM+FMS patients. CSI scores were higher in CM+FMS patients (p < 0.001). SF-36 sub-cores, including physical function, energy/fatigue, emotional well-being, and general health scores, were lower in CM+FMS patients (p < 0.05). Sleep duration was significantly lower and use of medication to sleep was more common in same group (p < 0.05). FIQ score in CM+FMS patients was associated with quality of life scores, sleep quality, anxiety, and central sensitization scores (p < 0.05).

CONCLUSION

In patients with chronic migraine, FMS comorbidity negatively affects the quality of life and significantly increases central sensitization.

Functional connectivity associated with attention networks differs among subgroups of fibromyalgia patients: an observational case-control study

Fibromyalgia is a heterogenous chronic pain disorder diagnosed by symptom-based criteria. The aim of this study was to clarify different pathophysiological characteristics between subgroups of patients with fibromyalgia. We identified subgroups with distinct pain thresholds: those with a low pressure pain threshold (PL; 16 patients) and those with a normal pressure pain threshold (PN; 15 patients). Both groups experienced severe pain. We performed resting-state functional MRI analysis and detected 11 functional connectivity pairs among all 164 ROIs with distinct difference between the two groups (p < 0.001). The most distinctive one was that the PN group had significantly higher functional connectivity between the secondary somatosensory area and the dorsal attention network (p < 0.0001). Then, we investigated the transmission pathway of pain stimuli. Functional connectivity of the thalamus to the insular cortex was significantly higher in the PL group (p < 0.01 - 0.05). These results suggest that endogenous pain driven by top-down signals via the dorsal attention network may contribute to pain sensation in a subgroup of fibromyalgia patients with a normal pain threshold. Besides, external pain driven by bottom-up signals via the spinothalamic tract may contribute to pain sensations in another group of patients with a low pain threshold. Trial registration: UMIN000037712.

High mobility group box-1: A therapeutic target for analgesia and associated symptoms in chronic pain

The number of patients with chronic pain continues to increase against the background of an ageing society and a high incidence of various epidemics and disasters. One factor contributing to this situation is the absence of truly effective analgesics. Chronic pain is a persistent stress for the organism and can trigger a variety of neuropsychiatric symptoms. Hence, the search for useful analgesic targets is currently being intensified worldwide, and it is anticipated that the key to success may be molecules involved in emotional as well as sensory systems. High mobility group box-1 (HMGB1) has attracted attention as a therapeutic target for a variety of diseases. It is a very unique molecule having a dual role as a nuclear protein while also functioning as an inflammatory agent outside the cell. In recent years, numerous studies have shown that HMGB1 acts as a pain inducer in primary sensory nerves and the spinal dorsal horn. In addition, HMGB1 can function in the brain, and is involved in the symptoms of depression, anxiety and cognitive dysfunction that accompany chronic pain. In this review, we will summarize recent research and discuss the potential of HMGB1 as a useful drug target for chronic pain.

Heightened interoception in adults with fibromyalgia

Previous research suggests that the processing of internal body sensations (interoception) affects how we experience pain. Some evidence suggests that people with fibromyalgia syndrome (FMS) - a condition characterised by chronic pain and fatigue - may have altered interoceptive processing. However, extant findings are inconclusive, and some tasks previously used to measure interoception are of questionable validity. Here, we used an alternative measure - the Phase Adjustment Task (PAT) - to examine cardiac interoceptive accuracy in adults with FMS. We examined: (i) the tolerability of the PAT in an FMS sample (N = 154); (ii) if there are differences in facets of interoception (PAT performance, PAT-related confidence, and scores on the Private Body Consciousness Scale) between an FMS sample and an age- and gender-matched pain-free sample (N = 94); and (iii) if subgroups of participants with FMS are identifiable according to interoceptive accuracy levels. We found the PAT was tolerable in the FMS sample, with additional task breaks and a recommended hand posture. The FMS sample were more likely to be classified as 'interoceptive' on the PAT, and had significantly higher self-reported interoception compared to the pain-free sample. Within the FMS sample, we identified a subgroup who demonstrated very strong evidence of being interoceptive, and concurrently had lower fibromyalgia symptom impact (although the effect size was small). Conversely, self-reported interoception was positively correlated with FMS symptom severity and impact. Overall, interoception may be an important factor to consider in understanding and managing FMS symptoms. We recommend future longitudinal work to better understand associations between fluctuating FMS symptoms and interoception.

Improving the nosology of Long COVID: it is not so simple

Long COVID is a diagnostic label currently given to those suffering from a poorly understood state of incomplete recovery or who have development of a myriad of medically unexplained symptoms occurring in the wake of infection with SARS CoV-2 that is both poorly understood and controversial. Many of the features of one of the most common clinical endotypes of Long COVID are shared by a condition well familiar to all rheumatologists and one with a large body of epidemiologic, clinical and basic research accrued over many decades namely the syndrome of fibromyalgia. Some have recently suggested that Long COVID may merely be a new name for fibromyalgia and that this diagnosis is indeed the condition that many or most may be suffering from as a post infectious sequela. In this Viewpoint we argue that while the parallels between the clinical syndrome experienced by many of those currently labeled as Long COVID and fibromyalgia are strong we should be not too quick to rename the disorder. We further argue that relabeling Long COVID as fibromyalgia is clinically reductionistic and any such relabeling may be attended by harm in both the design and execution of a future research agenda as well to patients who may be inadvertently and unfortunately pejoritised by such labeling. We further explore the parallels and differences between Long COVID and fibromyalgia and outline areas of needed future research and care.

Naltrexone 6 mg once daily versus placebo in women with fibromyalgia: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Low-dose naltrexone is used to treat fibromyalgia despite minimal evidence for its efficacy. This trial aimed to investigate whether 12-week treatment with 6 mg low-dose naltrexone was superior to placebo for reducing pain in women with fibromyalgia.

METHODS

We did a single-centre, randomised, double-blind, placebo-controlled trial in Denmark. We enrolled women aged 18-64 years who were diagnosed with fibromyalgia. Participants were randomly assigned 1:1 to receive low-dose naltrexone (6 mg) or an identical-appearing placebo, using a computerised algorithm with no stratifications applied. Participants, investigators, outcome assessors, and statistical analysts were all masked to treatment allocation. The primary outcome was change in pain intensity on an 11-point numeric rating scale from baseline to week 12, in the intention-to-treat population. Safety was assessed in participants in the intention-to-treat population who received at least one dose of their allocated intervention. This trial was registered with ClincalTrials.gov (NCT04270877) and EudraCT (2019-000702-30).

FINDINGS

We screened 158 participants for eligibility from Jan 6, 2021, to Dec 27, 2022, and 99 patients were randomly assigned to low-dose naltrexone (n=49) or placebo (n=50). The mean age was 50·6 years (SD 8·8), one (1%) of 99 participants was Arctic Asian and 98 (99%) were White. No participants were lost to follow-up. The mean change in pain intensity was -1·3 points (95% CI -1·7 to -0·8) in the low-dose naltrexone group and -0·9 (-1·4 to -0·5) in the placebo group, corresponding to a between-group difference of -0·34 (-0·95 to 0·27; p=0·27, Cohen's d 0·23). Discontinuations due to adverse events were four (8%) of 49 in the low-dose naltrexone group and three (6%) of 50 in the placebo group. 41 (84%) of 49 patients in the low-dose naltrexone group had an adverse event versus 43 (86%) of 50 in the placebo group. One serious adverse event occurred in the placebo group and no deaths occurred.

INTERPRETATION

This study did not show that treatment with low-dose naltrexone was superior to placebo in relieving pain. Our results indicate that low-dose naltrexone might improve memory problems associated with fibromyalgia, and we suggest that future trials investigate this further.

FUNDING

The Danish Rheumatism Association, Odense University Hospital, Danielsen's Foundation, and the Oak Foundation.

Is fibromyalgia an autoimmune disorder?

Fibromyalgia (FM) is a multifactorial syndrome which includes not only widespread pain and stiffness, now recognized as major symptoms, but also numerous other somatic, emotional, and neuropsychic manifestation. The lack of specific validated biological and instrumental biomarkers has made FM a condition of unexplained medical significance, and its pathophysiology remains controversial and subject to debate. The current hypothesis regarding the pathogenesis of FM proposes that its development is influenced by various mechanism, including genetic predisposition, stressful life events, inflammatory processes, and cognitive-emotional factors. However, despite the extensive research conducted to date, the available data do not provide a clear understanding of the pathogenesis of FM. In this article, we report the opposing viewpoints of two leading experts who debate the question of whether FM is an autoimmune disease, based on scientific data regarding this condition. Both perspectives are discussed and the latest evidence on the pathophysiology of FM is reported to provide a comprehensive understanding of this complex syndrome.

The crosstalk of the pathophysiologic models in fibromyalgia

Fibromyalgia (FM) is a heterogeneous condition with various mechanisms (endotype) and manifestations (phenotypes). Many worthy endeavors have been dedicated to exploring the main trajectories of FM pathogenesis, depicted as the models of FM development. The Imbalance of Threat and Soothing Systems (FITSS) model, which is an advancing psychosocial form of the "central sensitization" model, and autonomic nervous system (ANS) model, besides new discoveries of potential pathways for FM development such as autoimmunity, small fiber pathology, and gut-brain axis currently comprise all our knowledge assets about FM pathogenesis. The pathophysiology of fibromyalgia is too complex to justify with one model, one main loop of pathogenesis, and one terminator. It appears that the variable FM models could justify some phenotypes of FM. Currently, our knowledge about FM pathogenesis and trying to match the different pathways and links mimic solving a puzzle in the hands of beginners. Until unraveling many missed interconnections and formulas between numerous scrambled pieces of the FM puzzle, proposing an integrated model seems not possible. This review focuses on the main trajectories of FM pathogenesis proposed thus far and tries to illuminate the crosstalking between them. We also propose the subgrouping FM into more homogenous categories based on the endotype-phenotype characteristics. It could provide a more pragmatic approach toward understanding of the diverse network of FM pathogenesis as well as the personalized stratification of FM. Key Points • The disentangled nature of FM pathogenesis escapes from embracing under one integrated model. • There appears to be no way for formulizing FM pathogenesis except the acknowledgment of the different pathways and their crosstalk explored as yet. • Acknowledging the different endotypes/phenotypes of FM spectrum and classifying them into more homogenous groups can help to the pragmatic approach to FM.