The Journal of Pain

Treatments for chronic low back pain (LBP) provide only small improvements in pain and disability compared with placebo. Targeting mechanisms involved in the persistence of pain and disability following an episode of acute LBP (ALBP) may enhance treatment effectiveness. Sensorimotor alterations have been observed in individuals with chronic LBP (CLBP), but their role in the development of CLBP remains unclear. In this secondary analysis of longitudinal data from 99 participants with ALBP, the causal associations between pain sensitivity and erector spinae muscle activation measured in the acute phase of LBP and pain and disability at 6- and 12-month follow-ups were explored. Negative binomial regressions revealed that greater lumbar muscle activation at baseline was associated with lower disability at 6 months (incidence rate ratio [IRR] 0.33 [95% CI 0.13 to 0.85], p=0.02). Higher lumbar pressure pain threshold was also associated with lower disability at 6 months (IRR 0.87 [95% CI 0.79 to 0.97], p=0.009). At 12 months, greater lumbar and thoracic muscle activation were associated with lower disability (IRR 0.11 [95% CI 0.03 to 0.35], p<0.001 and IRR 0.09 [95% CI 0.02 to 0.33], p<0.001, respectively). The findings suggest that increased thoracolumbar muscle activation during the acute phase may act as a protective mechanism and support recovery. However, the association with pain sensitivity should be interpreted with caution, as only one of 16 models reached statistical significance. Longitudinal studies assessing the evolution of these sensorimotor factors could improve the understanding of their contribution in the development of CLBP. Perspective: This article presents exploratory analyses of causal associations between sensorimotor outcomes in acute low back pain and levels of pain and disability in the long-term. Increased muscle activation explained better long-term outcomes, whereas increased pain sensitivity explained poorer long-term outcomes.

Introduction: Pain catastrophizing and pain self-efficacy are well-established predictors of health outcomes in chronic pain. Higher pain catastrophizing, a maladaptive cognitive process, predicts worse health outcomes, whereas higher pain self-efficacy, an adaptive cognitive process, predicts better health outcomes. This study examined whether pain catastrophizing and pain self-efficacy interactions predict physical and psychosocial health outcomes at 3 months and their change over 3-months among patients with chronic pain who sought care at a tertiary pain clinic. Methods: Adults with chronic pain (N = 181; 66.7% female; Mage = 58.7) completed baseline assessments of the Pain Catastrophizing Scale (PCS), Chronic Pain Self-Efficacy Scale (CPSS), and PROMIS measures of physical (pain intensity, pain interference, physical function) and psychosocial health (depression, anxiety, anger, loneliness). PROMIS measures were repeated at 3 months. Hierarchical multiple regression analyses tested PCS, CPSS, and their interaction as predictors of outcomes at 3 months and change scores from baseline to 3 months. Results: The PCS by CPSS interaction significantly improved prediction for physical function (Change in R2 = 0.02, p = .02). Higher baseline self-efficacy predicted better physical function (Beta = 0.65, p < .001), but this effect weakened with higher levels of pain catastrophizing. The interaction also predicted change scores in physical function (p = .025) but was marginal after false discovery rate correction (p = .059). Additionally, a significant interaction emerged for loneliness change scores (p = .01): higher self-efficacy predicted greater reductions in loneliness, attenuated by higher catastrophizing. Conclusion: Pain self-efficacy interacted with pain catastrophizing to predict physical function and loneliness at 3 months. Greater self-efficacy was associated with better outcomes, with associations diminished with higher levels of pain catastrophizing. Findings highlight the moderating role of adaptive and maladaptive cognitions and suggest interventions should address both processes to optimize recovery in physical and social functioning.

Background: Heatwrap is recommended for acute low back pain (ALBP), and previous research found heatwrap plus exercise more effective than each intervention alone. While recommended by clinical guidelines, their impact on mechanistic outcomes is unknown. This trial aimed to (i) assess immediate and short-term effects of heatwrap alone or combined with exercise, compared with a sham heatwrap, on pain sensitivity, lumbar muscle activity, current pain intensity, and trunk flexion range of motion, and (ii) explore whether changes in pain sensitivity and lumbar muscle activity are associated with changes in clinical symptoms from baseline to 1-week follow-up. Methods: A randomised controlled trial took place at a single research center. Of 315 individuals screened for eligibility, 99 adults with ALBP were recruited and assigned to one of three intervention groups: heatwrap plus exercise (n=34), heatwrap alone (n=33) or sham heatwrap (n=32). Interventions were applied for one hour at the first visit, and immediate effects were measured. Then, interventions were applied for 7 days, and short-term effects were measured at 1-week follow-up. Outcomes included pressure pain threshold, temporal summation of pain, flexion-relaxation ratio, trunk range of motion and current pain intensity. Results: Heatwrap and exercise did not produce greater effects over time than heatwrap alone or a sham heatwrap on all outcomes, and changes in sensorimotor outcomes at one week were not associated with changes in symptoms. Conclusions: Heatwrap and/or exercises did not influence specifically the potential sensorimotor mechanisms tested in individuals with ALBP. Trial registration: ClinicalTrials.gov; registration number: NCT03986047

Validated measures of pain catastrophizing primarily assess catastrophizing as a stable trait. However, emerging evidence suggests catastrophizing fluctuates with context, highlighting a need for ecologically valid methods to capture it. This study evaluated large language models (LLMs) as implicit markers of catastrophizing from free text responses from ninety-one adults with chronic pain receiving long-term opioid therapy (57.3 percent Female; mean age = 60.5 years). Patients completed baseline measures, including the trait pain catastrophizing scale (PCS), followed by a 10 minute writing task after random assignment to a negative, positive, or neutral pain-coping condition. State affect and pain were assessed before and after writing tasks and again after a cold pressor task (4 degrees C; <= 2 minutes). A state PCS followed the cold pressor task. Free text responses were analyzed using four LLMs (Claude Opus 4; GPT Mini 4o; Llama 4 Maverick; and Gemini 2.5 Pro). ANOVA based results supported discriminant validity, as all four LLM-derived pain catastrophizing scores differentiated negative from positive and neutral pain-coping conditions. Convergent validity was model dependent; only Gemini derived scores correlated with state catastrophizing (r = .22) and pain unpleasantness (r = .23). Divergent validity was mixed. LLM derived scores were unrelated to pain intensity, but Gemini and Claude derived scores showed small correlations with trait PCS (rs = .21; 28, respectively). All LLM-derived scores also correlated with negative affect (rs range = .29 - .41), comparable in magnitude to state PCS, suggesting limited specificity. These findings provide preliminary evidence that certain LLMs may serve as implicit markers of state pain catastrophizing, but further study is needed.

Introduction: Acute low back pain is a leading cause of disability worldwide. Clinical guidelines recommend non-pharmacological therapies as first-line treatment and advise caution with opioid prescribing. However pharmacological therapies, including opioids and gabapentinoids, remain commonly used. The comparative risks of subsequent opioid use disorder (OUD) and overdose diagnosis associated with initial treatment modality in large, real-world populations is not well characterized. We estimated the incidence of new-onset OUD and overdose diagnosis among opioid-naive, Medicaid-insured adults with newly diagnosed acute low back pain and estimated the association between initial treatment modalities and subsequent OUD and overdose diagnosis risk. Methods: We conducted a retrospective cohort study using Medicaid T-MSIS Analytic files from 25 states (2016-2019). We identified opioid-naive adults with a new diagnosis of acute low back pain who initiated pharmacologic or non-pharmacologic treatment within 1 month of diagnosis. The primary outcome was incident OUD and overdose diagnosis (based on diagnosis codes in claims) during follow-up. Associations between initial treatment modality and OUD and overdose diagnosis risk were estimated using a non-parametric, doubly robust estimator to adjust for measured confounding. Results: The cohort included 525,002 opioid-naive adults initiating treatment for low back pain. The cumulative incidence of OUD and overdose diagnosis was 1.5% and 2.4% at 7 and 13 months, respectively. Compared to non-use, use of gabapentinoids during the first month of treatment was associated with the highest relative risk (increasing risk) by 130.1%, 95% confidence interval (CI): 117.8%, 142.3%), the second-highest relative risk was estimated for higher-dose opioids, defined as > 50 daily Morphine Milligram Equivalents (MME) (118.1%, 95% CI: 99.2%, 137.0%). Lower-dose, short-duration opioids ([&le;] 50 MME, [&le;] 7 days) were also associated with elevated risk, though substantially smaller in magnitude (20.8%, 95% CI: 13.8%, 27.9%). In contrast, non-pharmacologic, non-interventional therapies were associated with reduced OUD and overdose diagnosis risk, with physical therapy demonstrating the largest relative reduction of 34.0% (95% CI: -40.9%, -27.1%). Discussion: In opioid-naive Medicaid patients with acute low back pain, initial non-pharmacologic treatment was associated with reduced OUD and overdose diagnosis risk. Gabapentinoids and opioids were each associated with increased risk; for opioids, the degree of risk increased with higher doses and durations. These results support guideline recommendations favoring non-pharmacologic treatment as first-line therapy and indicate the importance of cautious prescribing when pharmacologic treatment is considered.

Chronic widespread pain (CWP) is highly prevalent among minoritized adults with clinical obesity, and symptom management is challenging. Weight loss via bariatric surgery is often recommended to improve musculoskeletal pain. However, there is significant variation in pain trajectories following bariatric surgery, and the impact of weight loss on movement-evoked pain is largely unknown. The current study aims to systematically characterize and quantify longitudinal changes in pain at rest and movement-evoked pain up to 6 months post-surgery, and to determine whether pain modulatory mechanisms, joint motion, and mechanical loading biosignatures mediate the relationship between weight loss and pain change. This study protocol details the research methodologies and procedures for a prospective observational cohort study of 60 individuals undergoing bariatric surgery for weight loss. Participants will complete questionnaires, anthropometric measurements, clinical and experimental pain testing, functional testing, and a standardized movement testing battery to assess joint motion and mechanical loading using camera-based motion capture before and at 3 and 6 months post-bariatric surgery. Generalized linear mixed models to assess the significance of changes in PAR, MEP, and all patient-reported outcome measures. Reduced models will treat the main effect of time as a fixed factor, and intra-individual repeated measures as random effects. Ethics and dissemination: This study protocol has been registered as an observational study with ClinicalTrials.gov (NCT0675386) in the United States and has been approved by the NYU Langone Health Institutional Review Board (IRB#: i21-01652) and the New York City Health + Hospitals/Bellevue Research Office (Bellevue Study ID #: STUDY00003739). Study results will be published in peer-reviewed journals and presented at national and international conferences and community events.

Background: Fluctuations in pain intensity are intrinsic to non-specific chronic low back pain (nsCLBP). Nevertheless, pain fluctuations have rarely been considered when investigating pathophysiological mechanisms. Therefore, a novel study protocol was developed and implemented to systematically assess the impact of fluctuating pain states on pain-related measures. Methods: The final study cohort consisted of 45 nsCLBP patients and 47 age- and sex-matched healthy controls (HCs). Patients participated in three visits, conducted during different pain states (i.e. clinically relevant pain, low-intensity clinical pain / pain-free, clinically irrelevant pain induced using a Qutenza 8% capsaicin patch). Pain fluctuations were monitored through online assessments every four days and guided the pseudorandomized visit scheduling. HCs participated in a single visit. Each study visit comprised a multimodal battery of pain-related measures. Results: 93.33% of patients completed all three visit types in a pseudorandomized order (chi-squared=1.50, p=0.826). Visit scheduling was possible due to the high self-report adherence (median=93.48%), unrelated to self-report burden (rho=-0.097, p=0.53). Study visits were conducted during different pain states, as indicated by: i) the significantly higher low back pain intensity in the clinically relevant pain visit (mean[SD]: 3.98[0.90]), compared to the low-intensity clinical pain (1.03[0.86]) and clinically irrelevant pain (1.13[0.82]) visits (p-values<0.001), as well as by ii) the successful induction of a moderate-to-high clinically irrelevant pain across assessments. Conclusion: Despite scheduling complexity and pain state transition uncertainty, a pain state-dependent pseudorandomized study design is feasible and could improve the understanding of nsCLBP mechanisms.

Understanding the complex network that regulates pain is fundamental to develop strategies to combat its growing prevalence and increase useful therapeutics. Although extensive literature identifies the importance of cannabinoid receptors and endocannabinoids in controlling pain, their efficacy and loci of action remain debated. To directly test the actions of peripherally restricted cannabinoids and elucidate the minimal circuitry capable of producing cannabinoid-mediated analgesia, we utilized a novel genetic approach that allows for cell-specific reactivation of cannabinoid receptor 1 (CB1R) selectively in peripheral sensory neurons using newly developed CB1R floxed-stop-floxed mice (CB1RLOXTB) crossed with Nav1.8-cre mice (Nav1.8+/-:CB1RLOXTB). Ex vivo and in vivo experiments confirmed successful knockout and reactivation of CB1R. Wildtype littermate controls, but neither Nav1.8+/-:CB1RLOXTB nor CB1RLOXTB animals, exhibited robust analgesia after systemic WIN55,212-2 (WIN) treatment in the tail flick assay. Furthermore, the presence of CB1R on Nav1.8 neurons was not associated with either a difference in the development of inflammatory pain or the response to WIN. However, after neuropathic injury, CB1RLOXTB animals displayed an earlier onset of both mechanical and thermal hypersensitivity than their Nav1.8+/-:CB1RLOXTB or wildtype counterparts, suggesting a dual role for CB1R in inflammatory and neuropathic pain. These studies represent an important approach to further improve our mechanistic understanding of cannabinoid modulation of pain in the nervous system and begins to settle long-standing controversies in cannabinoid literature. Table of ContentsPeripherally restricted cannabinoids show strong preclinical analgesic efficacy but have not translated clinically. Using a genetic model restricting CB1R to Nav1.8-expressing sensory neurons, we show peripheral neuronal endocannabinoid signaling is required for chronic, but not acute pain modulation. This dissociation suggests clinical failures may reflect testing peripheral cannabinoids in acute rather than chronic pain paradigms, informing future translational strategies.

Background. Chronic pelvic pain with involuntary pelvic-floor hypertonicity is common, disabling, and inconsistently measured, and no validated condition-specific severity instrument exists. A refractory subset has been proposed to represent a focal dystonia of the pelvic musculature, termed pelvic dystonia. Purpose. To develop the Pelvic Dystonia Severity Scale (PDSS) and evaluate its measurement properties as a patient-reported measure of pelvic-pain symptom severity and burden, following the COSMIN guidelines. Methods. Cross-sectional study with a test-retest component in 102 adults from an outpatient multidisciplinary pain practice. We assessed data quality, structural validity, internal consistency, test-retest reliability, measurement error, and construct validity against the Global Dystonia Severity Rating Scale (GDS) and Brief Pain Inventory (BPI). Because no validated diagnostic criteria exist, a clinician blinded to PDSS responses rated each participant for clinical signs of pelvic dystonia (present/possible/absent) as a provisional reference standard. Results. 100 of 102 participants (98%) returned complete data, with 0% item-level missing data. Factor analysis supported a unidimensional structure (single factor, 68.6% of variance; loadings 0.56-0.93), with high subscale intercorrelations (r = 0.81-0.97). Internal consistency (Cronbach's 0.810-0.924) and test-retest reliability (ICC 0.857-0.953) were strong. Convergent validity was supported by correlations with GDS pelvic-region items (r = 0.56-0.68) and BPI severity (r = 0.44-0.55), and discriminant validity by weak correlations with anatomically remote regions (shoulder/arm r = 0.03-0.16). PDSS scores rose monotonically across blinded clinical-signs categories (absent 14.9, possible 32.7, present 52.0; Kruskal-Wallis p < 0.001), discriminating signs-present from signs-absent participants with a very large effect (Hedges g = 2.19; ROC AUC = 0.92). Conclusion. The PDSS is a psychometrically robust, unidimensional measure of pelvic-pain symptom severity and burden with strong data quality, reliability, and construct validity. It is suitable for characterizing symptom severity and, pending responsiveness testing, for monitoring treatment. The dystonia interpretation of the underlying phenotype is discussed as a hypothesis for future neurophysiologic and longitudinal study.

Abstract Background: Non-specific chronic low back pain (NSCLBP) is a major cause of disability worldwide and is associated with low-grade systemic inflammation. This study investigated the effects of aerobic exercise on inflammatory biomarkers, pain intensity, and quality of life among individuals with NSCLBP. Methods: In this parallel-group randomized controlled trial, 41 participants with NSCLBP were allocated to either an aerobic exercise plus health education group (n=21) or a health education-only control group (n=20). Participants in the intervention group completed supervised aerobic cycling three times weekly for 12 weeks. Outcome assessors and laboratory personnel were blinded to group allocation. Outcomes were measured at baseline, Week 8, and Week 12. Results: Interaction effects were observed for TNF- (p=0.046), IL-6 (p<0.001), hs-CRP (p<0.001), and pain intensity (p<0.001). Significant improvements were also observed across all WHOQOL-BREF quality-of-life domains (all p<0.05). After adjustment for baseline values and age, participants in the intervention group had significantly lower Week 12 IL-6 (p=0.013), hs-CRP (p<0.001), and pain intensity (p<0.001) than controls. No serious adverse events were reported. Conclusions: Aerobic exercise combined with health education produced greater improvements in inflammatory biomarkers, pain intensity, and quality of life than health education alone among individuals with NSCLBP. These findings support the integration of structured aerobic exercise into rehabilitation programmes for chronic low back pain. Keywords: Non-specific chronic low back pain; aerobic exercise; inflammation; IL-6; hs-CRP; pain intensity; quality of life; randomized controlled trial.

Abstract Background: Non-specific chronic low back pain (NSCLBP) is associated with persistent pain, reduced health-related quality of life (HRQoL), and low-grade systemic inflammation. This study examined associations among changes in inflammatory biomarkers, pain intensity, and HRQoL following a 12-week aerobic exercise programme. Methods: This secondary analysis used data from a randomized controlled trial involving 41 participants with NSCLBP (intervention, n = 21; control, n = 20). Participants received either supervised aerobic exercise plus health education or health education alone for 12 weeks. Change scores for tumour necrosis factor-alpha (TNF-), interleukin-6 (IL-6), high-sensitivity C-reactive protein (hs-CRP), pain intensity, and HRQoL domains were analysed using correlation and multiple regression analyses. Results: Improvements in IL-6 (r = 0.434, p = 0.005) and hs-CRP (r = 0.444, p = 0.004) were significantly associated with improvements in pain intensity. No significant associations were observed between biomarker changes and HRQoL domains. Treatment allocation was the strongest independent predictor of improvement in physical HRQoL ({beta} = 0.492, p = 0.017) and pain intensity ({beta} = -0.512, p = 0.006). Conclusions: Improvements in IL-6 and hs-CRP were associated with reductions in pain intensity but not with improvements in HRQoL. Treatment allocation was the strongest predictor of clinical improvement, suggesting that mechanisms beyond systemic inflammation may contribute to the benefits of aerobic exercise in NSCLBP. Keywords: non-specific chronic low back pain; aerobic exercise; inflammation; interleukin-6; high-sensitivity C-reactive protein; pain intensity; health-related quality of life.

Cannabidiol (CBD) is a non-psychoactive component of cannabis that has been studied as a potential therapy for chronic pain. CBD attenuates behavioral hypersensitivities in models of neuropathic pain, and promotes production of bioactive lipids (e.g., anandamide), altering lipid signaling. However, a lack of understanding of the mechanisms underlying the therapeutic effects of CBD has hindered development and application of CBD to mechanism-based therapies for pain in people. We asked whether the analgesics effects of CBD were dependent upon the enzyme NAPE-PLD. We used a mouse model of chemotherapy-induced peripheral neuropathy (CIPN) to evaluate the acute and chronic antinociceptive effects of CBD and investigate its mechanisms. Pharmacological specificity was tested with antagonists targeting CB1, CB2, PPAR{gamma}, and PPAR receptors. Mechanisms were further examined using NAPE-PLD and GPR55 knockout mice. We also assessed repeated CBD dosing during both the development and maintenance of paclitaxel-induced CIPN in wild-type, GPR55 KO, and NAPE-PLD KO mice. CBD suppressed paclitaxel-induced behavioral hypersensitivities; these effects were attenuated by a PPAR and PPAR{gamma} antagonists, but not CB1 or CB2 antagonists. CBD reduced both the development and maintenance of neuropathic nociception in a model CIPN in wild-type mice, but these effects were absent in NAPE-PLD KO mice. By contrast, anti-allodynic efficacy of CBD was fully preserved in GPR55 KO mice. Pharmacological blockade of the PPAR receptor and genetic deletion of NAPE-PLD abolished the antinociceptive effects of CBD in a model of CIPN, suggesting a pivotal role for NAPE-PLD and PPAR receptors in CBD-mediated analgesia in chemotherapy-induced neuropathic pain.

Chronic pelvic pain (CPP) affects up to 26% of women worldwide. While its pathophysiology is poorly understood, disturbances in body perception have been identified in various similar chronic musculoskeletal disorders. The Fremantle Perineal Awareness Questionnaire (FrePAQ) is a novel tool designed to specifically assess disturbed body perception in the pelvic region, but its structural validity and reliability require formal evaluation. Methods: Patient partners with lived experience contributed to study design. Participants with (n=417 and without (n=277) chronic pelvic pain completed the FrePAQ at baseline, as well as one week later. We assessed the validity and reliability of the FrePAQ following COSMIN guidelines for Classical Test Theory. Results: The validated FrePAQ comprises a two factor model, with a six item Distress & Disconnection (D&D) subscale and a two item Size & Shape (S&S) subscale. Confirmatory analysis showed excellent fit (CFI = .988; RMSEA = .048) and measurement invariance between diagnostic groups. Internal consistency was high (cronbach alpha = .838 CPP, .819 controls). Test retest reliability was high for D&D (ICC = .863) and acceptable for S&S (ICC = .695). FrePAQ scores showed a weak to moderate correlation with pain scores (r = .234 to .255), psychological distress (r = .226 to .443), and functional impact (r = .172 to .295), particularly for the D&D subscale. Conclusion: The FrePAQ is a reliable and valid instrument to measure perineal perceptual disturbances in CPP. Future research will evaluate the tools potential to support phenotyping and guide individualised interventions. Improved understanding of body perception disturbance in CPP can enhance diagnosis and treatment precision.

Placebo analgesia varies substantially across individuals, yet the sources of this heterogeneity remain incompletely understood. Pain-reporting variability may represent an underrecognized predictor of placebo responsiveness. This study examined whether variability and reliability of pain reporting predict placebo analgesia in an experimental pain setting. Eight hundred and three participants (401 individuals with temporomandibular disorder and 400 healthy controls) completed a standardized thermal pain paradigm involving calibration, placebo conditioning, and testing phases. We obtained repeated heat temperatures (four) during thermal calibration and pain ratings during conditioning test (24 trials). We used these measurements to quantify within-person pain-reporting variability using standard deviation (SD) and coefficient of variation (CoV), and reliability using intraclass correlation coefficients (ICC). Placebo analgesia was calculated as the difference in pain ratings between control and placebo cue trials during testing. Regression models examined associations between reporter characteristics and placebo analgesia controlling for age, sex, race and experimenters. Variability of thermal pain responses during calibration did not predict placebo analgesia. Greater pain-reporting variability during conditioning was associated with reduced placebo analgesia (higher SD and CoV), and this effect was mediated by slower acquisition of the cue pain contingency. Conditioning-phase reliability was not associated with placebo analgesia, whereas three clusters of learning profiles predicted placebo effects. Thus, individual differences in pain-reporting variability during conditioning, rather than baseline sensory variability, contribute to heterogeneity in placebo analgesia. These findings suggest that variability during acquisition processing matters more than general sensory variability influencing the magnitude of placebo effects.

Patients with bowel disease can develop referred somatic pain at a later time with unknown molecular mechanisms. Using experimental mice with colitis induced by intracolonic installation of 2,4,6-Trinitrobenzenesulfonic acid (TNBS), we find an increase in the percentage of hind paw primary afferent neurons expressing Piezo2 or calcitonin gene-related peptide (CGRP), which are attenuated by TrkB.T1 knockout (KO). Concomitantly, TrkB.T1 KO also attenuates colitis-induced hind paw mechanical hypersensitivity and pain. Next, we find that TrkB.T1 is expressed in spinal cord astrocytes and its expression level is increased by colitis. TrkB.T1 KO reduces colitis-induced upregulation of Tumor necrosis factor-alpha (TNF-) mRNA but not upregulation of interleukin (IL)-6 mRNA in the spinal cord. Using calcium (Ca2+) imaging and ex vivo approaches, we find that TNF- elicits Ca2+ transients in capsaicin-sensitive as well as capsaicin-insensitive DRG neurons, and increases Piezo2 and CGRP expression in DRG neurons via distinct signaling pathways. Notably, TNF-or colitis-induced Piezo2 upregulation in L4 DRG neurons is mediated by or associated with the PI3K/Akt pathway that does not participate in CGRP upregulation. In contrast, CGRP upregulation in hind paw primary afferent neurons is associated with an upregulation of phosphorylated cAMP response element binding protein (p-CREB). Finally, we find that TrkB.T1 KO does not change the expression level of transient receptor potential cation channel subfamily V member 1 (TrpV1) in L4 DRG in colitis, explaining the ineffectiveness of TrkB.T1 KO on colitis-induced hind paw thermal hyperalgesia. These results suggest complex and distinct molecular pathways in colitis-induced somatic pain modalities and provide information for specific pain modality management.

Background: Chronic pain is a multidimensional condition that often persists despite conventional treatment and adversely affects multiple domains of daily life. Music listening has emerged as a promising non-pharmacological intervention, with accumulating evidence supporting its beneficial effects on pain and associated psychological outcomes. However, despite growing evidence of efficacy, the translation of music listening into routine clinical practice remains limited, partly because intervention reporting has received comparatively little attention. Objective: To evaluate the effectiveness of music listening interventions for chronic pain and systematically assess the methodological quality and completeness of intervention reporting to identify barriers to reproducibility and clinical implementation. Methods: Systematic searches were conducted in PubMed, Cochrane Library, CINAHL, and Web of Science through June 2025, with no date restrictions on publication. Randomized controlled trials involving adults with chronic pain receiving music listening interventions were included. Two independent reviewers screened studies, extracted data, and assessed risk of bias. Intervention reporting was evaluated using the TIDieR checklist, and a random-effects meta-analysis was performed for pain intensity outcomes. Results: Ten RCTs involving 538 participants were included. Music listening interventions varied substantially in delivery, duration, and music selection procedures, reflecting considerable heterogeneity in intervention design. Most studies reported significant improvements in pain and psychological outcomes. Meta-analysis of eight trials (10 effect estimates), demonstrated a moderate reduction in pain intensity (SMD = -0.53, 95% CI: -0.96 to -0.11, p = 0.014; I2 = 76.2%). Although intervention rationale and procedures were generally well described, reporting of intervention modifications, treatment fidelity, and adherence was frequently incomplete. These reporting deficiencies may compromise reproducibility and limit translation into clinical practice. Conclusions: Music listening appears to be a safe, accessible, and scalable non-pharmacological intervention for chronic pain management, with benefits extending beyond pain reduction to psychological wellbeing, quality of life, and functioning. However, incomplete reporting of key intervention components may limit reproducibility and hinder clinical implementation. Future trials should adopt standardized and transparent reporting standards to facilitate implementation into clinical practice.

The Acute to Chronic Pain Signatures (A2CPS) project is a large, multisite, longitudinal observational study designed to identify biomarkers that predict the transition from acute to chronic pain following surgery in more than 2200 patients. Two participant cohorts were recruited before undergoing either knee arthroplasty or thoracic surgery. A unique feature of this study is its comprehensive evaluation of pain, including evoked and recall pain measures collected at baseline, 6-weeks, and 3-months following surgery, in addition to the primary pain outcome assessed remotely at 6 months. This paper describes the acquisition, quality control procedures, and available pain and pain sensitivity variables included in the A2CPS study. Self-report pain assessments include surgical site (i.e., index) pain intensity, pain interference and quality, spatial distribution of pain using body maps, and pain-related dysfunction specific to each cohort. Quantitative sensory testing yielded evoked pain sensitivity data including pressure pain thresholds, temporal summation of pain, dynamic mechanical allodynia, and conditioned pain modulation at both index and common sites across cohorts. Movement-evoked pain was assessed for each cohort using relevant functional tasks (knee: 10m walk and five-time-sit-to-stand tests, thoracic: deep breathing and coughing). Using baseline data from release v2.1.0, comprising approximately 1,400 participants, we evaluated interrelationships among pain variables. Overall, the A2CPS pain and pain sensitivity data provide a robust, comprehensive set of variables that supports the study goal of uncovering predictive biomarkers of post-operative chronic pain and enables broader exploration relative to other study outcomes, including imaging, psychosocial, and omics data.

The kappa opioid receptor (KOR) has emerged as a promising, nonaddictive analgesic target, yet the neural mechanisms underlying KOR inhibition of pain are not entirely understood. Here, we provide converging evidence that KOR expressed on spinal neurons inhibits acute pain. We demonstrate that pharmacological inhibition of KOR-expressing neurons in the spinal cord blocks nocifensive behaviors. Conversely, chemogenetic activation of KOR-expressing spinal neurons elicits nocifensive behaviors. We then perform a series of molecular characterizations and show that excitatory KOR spinal neurons are recruited by noxious stimuli and coexpress pain-promoting neuropeptides such as Tac1 in both mouse and human. Together, these data suggest that kappa opioids inhibit pain by reducing the release of pain-promoting neuropeptides from a translationally relevant population of spinal neurons.

Chronic pain is highly heterogeneous, with individuals varying substantially in symptoms. pain severity, disability, affective distress, cognitive functioning, and trauma-related symptoms. This study examined whether working memory, post-traumatic stress symptoms (PTSS), trauma exposure, and pain modulation explain distinct or shared dimensions of chronic pain variability. Individuals with chronic pain completed clinical, cognitive, trauma-related, and behavioural pain modulation measures, as well as resting-state functional magnetic resonance imaging. Multivariate regressions were used to determine whether working memory, PTSS, trauma exposure, and pain modulation independently predicted chronic pain outcomes. Principal component analysis was used to identify latent dimensions of chronic pain, and mediation analyses tested whether behavioural pain modulation explained relationships between dlPFC to vlPAG resting-state functional connectivity and clinical pain outcomes. PTSS independently predicted affective outcomes, including depression, state anxiety, and trait anxiety, whereas working memory independently predicted pain severity and pain interference. Trauma exposure was associated with greater PTSS and poorer working memory, but did not independently predict core pain outcomes after accounting for these more proximal factors. Principal component analysis identified partially distinct affective and sensory-disability dimensions, while trauma exposure loaded primarily on a separate component characterized by greater PTSS and poorer working memory. Behavioural pain modulation showed broader relationships across symptom dimensions and was associated with dlPFC to vlPAG connectivity. Exploratory mediation analyses demonstrated that pain modulation mediated relationships between dlPFC to vlPAG connectivity and both pain severity and affective distress. These findings support an integrated model where PTSS and working memory are more proximal predictors of affect and severity respectively, and trauma exposure represents a more distal vulnerability factor that predicts both. Thus, pain modulation represents a shared mechanism linking cortico-brainstem connectivity to chronic pain intensity and affect. These variables need further testing for phenotyping people with chronic pain based on their specific clinical needs.

Chemotherapy-induced peripheral neuropathy (CIPN) is a common and painful side effect of paclitaxel (PTX) treatment. The most common measures of painful neuropathy focus on evoked mechanical hypersensitivity, but clinically relevant ongoing pain remains understudied in preclinical models. Automated machine learning methods for pose estimation and behavioral classification have been proposed to capture non-evoked pain-like behaviors, though these approaches have primarily been applied to unilateral injury models such as spared nerve injury or unilateral inflammatory compound injection. Here, we evaluated the extent to which paclitaxel-induced CIPN affects the posture and spontaneous behavior of freely moving mice using a commercially available automated recording system (BlackBox). We found that paclitaxel-treated mice develop a broad and reproducible behavioral and postural phenotype relative to vehicle-treated controls, characterized by reduced front paw luminance and print size, increased front paw lifting, and altered body measurements consistent with a guarded posture. This phenotype was replicated across two independent cohorts and was detectable at both day 2 and day 6 following the final paclitaxel injection. To identify behavioral features specific to CIPN, we administered gabapentin, an analgesic often used to treat neuropathic pain in patients, to determine whether paclitaxel-induced behavioral changes could be attenuated. Gabapentin reduced several behavioral features in both paclitaxel-treated and vehicle-treated animals, suggesting that its effects on posture and gait are not specific pain in CIPN. These findings demonstrate that automated behavioral recording captures a robust paclitaxel-induced postural phenotype but question whether captured behaviors are indicative of ongoing pain as alleviated by gabapentin.