Children are at increased risk of developing chronic abdominal pain if a parent has an abdominal pain-related disorder of brain-gut interaction such as irritable bowel syndrome, suggesting family mechanisms of intergenerational pain transmission. However, patterns of family risk and resilience factors that predict children's vulnerability for developing chronic abdominal pain remain unknown. In a sample of parents with an abdominal pain-related disorder of brain-gut interaction and their young child without chronic pain, this cross-sectional study identified subgroups representing different constellations of family risk and resilience factors. It also tested subgroup differences on two vulnerability markers for children's future development of chronic abdominal pain: child emotional functioning and parental protective behavior. Baseline data from 212 parents and their 4-7-year-old child, participating in a randomized controlled trial testing a preventative intervention were included. Latent mixture modeling indicated a 3-group solution: (1) "High Socioeconomic Status, High Functioning" (55%) characterized by lower anxiety and depression and higher family resilience, (2) "Low Socioeconomic Status, High Pain Burden" (13%) characterized by higher pain catastrophizing and gastrointestinal symptoms, and (3) "High Socioeconomic Status, High Distress" (32%) characterized by higher parenting stress. Two of the three groups ("Low Socioeconomic Status, High Pain Burden" and "High Socioeconomic Status, High Distress" groups) showed lower child emotional functioning, and the "Low Socioeconomic Status, High Pain Burden" group also showed higher parental protective behavior, than the "High Socioeconomic Status, High Functioning" group. Results contribute to theoretical models of intergenerational pain transmission and help identify families who could benefit from preventative interventions. PERSPECTIVE: Among families of parents with chronic abdominal pain, low family resilience, low socioeconomic status, high parent pain burden, and high parent psychological distress may make young children more vulnerable to developing chronic abdominal pain in the future. These findings inform targeted interventions to prevent intergenerational transmission of abdominal pain.

Up to 30% of adolescents with acute musculoskeletal (MSK) injuries develop chronic pain. Research has increasingly focused on identification of risk factors associated with outcomes following acute injury; however, prospective longitudinal studies examining both psychophysical and biobehavioral factors beyond short-term follow-up are limited in adolescents. The current study used mixed effects models (MEM) to test longitudinal associations among biobehavioral factors (e.g., sleep disturbances, anxiety and depressive symptoms, pain-related cognitions and behaviors), psychophysical responses (e.g., conditioned pain modulation, temporal summation) and pain-related outcomes (pain intensity, pain-related disability and quality of life; QOL) over one year following acute MSK injury. Participants were 226 adolescents 11-17 years (and one parent) participating in a prospective longitudinal study with data collected via self-report, actigraphy and quantitative sensory testing (QST) at three timepoints (< 30 days, 3 months, 12 months post-injury). Results of MEM revealed within and between-person associations among psychological factors and pain-related disability and QOL. Sleep duration (within-person effect) and pain-related cognitions and behaviors (between-person effect) were associated with pain intensity. Pain-related cognitions and behaviors were also associated with pain-related disability (between-person effect) and QOL (within and between-person effects). Temporal summation (TS) was the only psychophysical factor associated with pain outcomes (between-person effect) with higher average TS associated with higher pain intensity. Findings point to the relatively stronger influence of biobehavioral (versus psychophysical) factors as responsive indicators of adolescents' recovery trajectories and suggest targeted interventions may be directed at general anxiety and depressive symptoms, pain-specific cognitions and behaviors, and sleep to improve outcomes. PERSPECTIVE: This article presents results of a longitudinal multi-method study examining pain-related outcomes in adolescents following musculoskeletal injury. Findings point to the influence of biobehavioral factors in the longer-term recovery period and suggest potential importance of interventions targeting general anxiety and depressive symptoms, pain-specific cognitions and behaviors, and sleep in adolescents post musculoskeletal injury.

Quantitative Sensory Testing (QST) measures how acute pain and sensation vary within and across individuals. It remains unclear how specific stimulus features, such as thermode type and stimulation duration, affect QST outcomes. We measured acute thermal pain in 93 healthy volunteers using three thermode types and two durations to assess potential impacts on QST outcomes. Across three experiments, participants completed two QST tasks, in which heat was applied to 8 sites on the left forearm. Thermode type (ATS, CHEPS, T03) and stimulus duration (3s, 8s) varied across tasks. We used linear regression to identify pain threshold, tolerance, and temperature-pain correlation (r[2]). Briefer stimuli were associated with higher pain tolerance (t(45) = 5.84, p < 0.001). Thermode type also influenced pain tolerance, such that tolerance was lower with higher surface area (t(45) = 4.79, p < 0.001). There was a weak effect of duration on pain Threshold. Pain threshold was higher in 3s duration than in 8s duration (t(45) = 2.25, p = 0.03). Neither duration nor thermode type affected temperature-pain correlation, and these effects did not differ by controlling for biological sex or task order (all p values > 0.05). These results demonstrate that QST outcomes are differentially sensitive to stimulus features, highlighting the importance of methodological standardization and the careful selection of suprathreshold stimuli in pain experiments. PERSPECTIVE: This study demonstrates the importance of considering stimulus features in "big data" approaches, as pain tolerance is significantly affected by stimulus duration and thermode type, whereas pain thresholds and temperature-pain correlations remain relatively stable.

Fear of movement and pain catastrophizing are associated with higher pain intensity and disability in adolescents with juvenile fibromyalgia (JFM), but it is unknown whether treatment-related reductions in these areas predict long-term outcomes. This study reports results of secondary data analyses from a multi-center randomized clinical trial (Fibromyalgia Integrative Training; FIT Teens) in which adolescents with JFM (N=317) received either cognitive-behavioral therapy (CBT), graded aerobic exercise, or CBT combined with neuromuscular exercise training. In the parent trial, functional disability of youth in all three treatments improved significantly at post-treatment and was maintained over one year. The objective of this study was to assess whether reductions in fear of movement and pain catastrophizing through 3-month follow-up predicted functional disability at 3- and 12-months. A novel latent curve modeling approach was employed to estimate distal outcomes across treatment groups. Results indicated that reductions in pain catastrophizing and fear of movement through 3-month follow-up both significantly predicted functional disability at the 3-month follow-up (p's<.05). However, only a reduction in fear of movement predicted functional disability at 12-months. Results support prioritizing strategies to reduce fear of movement in non-pharmacologic interventions for JFM which are associated with long-term improvements in function. PERSPECTIVE: Results of this study highlight the importance of assessing and addressing fear of movement among youth with widespread musculoskeletal pain. Treatments that include effective ways to improve movement confidence in adolescents with JFM may help optimize their long-term functional outcomes.

Visceral pain is a prevalent class of pain states that can depress normal behavior and reduce quality of life. Behavioral recovery is a goal of treatment, but pharmacotherapy is challenging, and refinement of preclinical visceral-pain endpoints could facilitate evaluation of novel candidate analgesics. Accordingly, the goal of the present study was to evaluate expression and treatment of pain-related locomotor depression in mouse models of visceral pain. Intracolonic 2,4,6-trinitrobenzenesulfonic acid (TNBS) and intraperitoneal cyclophosphamide (CYP) modeled colon and bladder pain, respectively, and these organ-targeted models were compared to intraperitoneal lactic acid (IP acid) as another more extensively evaluated visceral-pain model. Locomotion by male and female ICR mice was assessed in chambers with two compartments separated by a wire-mesh barrier that could be surmounted to cross between compartments. Primary dependent measures were vertical locomotion between compartments (Crosses) and horizontal locomotion represented by the sum of photobeam breaks within each compartment (Movement). Hunched posture and facial grimace were assessed as supplemental pain behaviors, and sensitivity of pain-related behaviors to the nonsteroidal anti-inflammatory drug ketoprofen and opioid agonist morphine were also examined. IP acid, TNBS, and CYP all produced depression of Crosses and Movement along with stimulation of hunched posture and grimace, although CYP effects were weaker than those of IP acid and TNBS. We have shown previously that IP acid effects can be blocked by ketoprofen and morphine, but both drugs were less effective against TNBS and CYP. The procedure described here could aid future efforts to discover improved pharmacotherapies for visceral pain. PERSPECTIVE: Visceral pain can depress normal behavior, and behavioral recovery is a treatment goal. This article compared locomotor depression produced by three visceral pain models in mice. All models depressed locomotion, but colon- and bladder-pain models were resistant to conventional analgesics. This procedure could aid development of improved visceral-pain pharmacotherapies.

This study identified 5-year pain trajectories in adult burn survivors and examined whether neighborhood-level socioeconomic disadvantage was associated with adverse trajectory membership. Using the Burn Model System National Database (2015-2025), Growth Mixture Modeling identified pain intensity trajectory classes in 1354 adults assessed at 6, 12, 24, and 60 months. In the geocoded subsample (n=909), multinomial regression with multiple imputation (m=100) estimated associations between the Area Deprivation Index (ADI) and trajectory membership, adjusting for demographic, clinical, and site characteristics and then additionally for individual socioeconomic characteristics. Three trajectories emerged: Low Pain (56%), Moderate Pain (30%), and High Pain (14%). Each 1-SD increase in ADI was associated with estimated relative risk ratios of 1.19 for Moderate Pain (95% CI 0.996-1.43, p=0.056) and 1.27 for High Pain (95% CI 0.99-1.63, p=0.058) versus Low Pain; both intervals included the null. Using Neighborhood Atlas ADI, disadvantage was associated with Moderate Pain (RRR 1.27, 95% CI 1.03-1.55) but not High Pain membership. Estimates were attenuated after additional socioeconomic adjustment. After correction for multiple comparisons, pre-injury unemployment and other public insurance (vs. private) were associated with higher High Pain risk, and household income of $50,000-$99,999 (vs. <$50,000) with lower Moderate Pain risk. Evidence was most consistent for persistent Moderate Pain, though estimates varied in precision across ADI measures. Individual socioeconomic characteristics were also associated with trajectory membership. PERSPECTIVE: Neighborhood disadvantage was associated with long-term pain after burn injury, with evidence most consistent for persistent moderate pain. Individual socioeconomic characteristics, including unemployment, income, and insurance, were also associated with trajectory membership. Neighborhood and individual socioeconomic information may guide sustained, multilevel support for burn survivors.

Cannabidiol (CBD) is a non-intoxicating phytocannabinoid with limited clinical evidence of its analgesic and opioid sparing effects. In the United States, the oral cannabidiol solution, Epidiolex®, is FDA-approved for intractable seizures. We conducted an off-label pilot randomized trial to evaluate its perioperative effects in patients undergoing bilateral total knee arthroplasty (BTKA). After IRB-approval and trial registration (NCT04749628), 36 patients were randomized to receive four perioperative doses of placebo (n=12), 400 mg (n=12) or 800 mg (n=12) oral CBD with standardized anesthesia and multimodal analgesia. The primary outcome was cumulative 72-hour opioid consumption (MME). Secondary outcomes included pain scores, adjunct analgesic use, inflammatory markers (IL-6), sleep, mood (HADS), safety, and pharmacokinetics. Dunnett's test showed no significant differences in 72-hour opioid consumption versus placebo (400 mg: 144 vs 209 MME, p=0.10; 800 mg: 203.2 vs 209 MME, p=0.98), although post hoc testing demonstrated lower opioid use with 400 mg CBD compared with placebo (p=0.04). The 400 mg group also had lower pain scores and fewer rescue analgesic requirements, but greater NSAID use. The 800 mg group showed no opioid-sparing effect and had greater adverse event burden. CBD groups reported improved subjective sleep domains, while anxiety and depression scores were higher, particularly at 800 mg. IL-6 levels were higher in CBD groups. Pharmacokinetic analyses confirmed measurable, dose-dependent exposure with substantial interindividual variability. These pilot data suggest a potential therapeutic signal at moderate dosing but not at higher doses. Larger trials are needed to confirm efficacy and define optimal dosing. PERSPECTIVE: Among BTKA patients, 400 mg cannabidiol reduced opioid use and pain while remaining tolerable, whereas higher dosing increased side effects, supporting further evaluation of CBD analgesia.

Chronic pain and cognitive concerns are highly comorbid, particularly among older adults, though the specific severity and symptom overlap may vary across individuals. We aimed to characterize distinct profiles of individuals with chronic pain and subjective cognitive concerns (concern of persistent cognitive decline, with or without objective cognitive deficits) and compare demographic/psychosocial variables between subgroups. We analyzed baseline data from an ongoing randomized controlled trial comparing a mind-body activity intervention to a health education control. As part of the larger study, older adults with chronic musculoskeletal pain and subjective cognitive concerns completed measures of pain severity (NRS), pain interference (PROMIS), and subjective (ECog-12) and objective cognitive dysfunction (RBANS). Participants also completed measures of mental health symptoms (anxiety, depression), general psychosocial factors (loneliness, mindfulness, self-compassion, coping skills), and pain-specific psychological factors (pain catastrophizing, kinesiophobia, pain self-efficacy). An exploratory hierarchical cluster analysis examined unique symptom profiles among participants with complete data (n=251) on the four pain/cognitive dysfunction variables, and multivariate logistic regression models examined cluster membership by demographic and psychosocial variables. We identified a three-cluster solution: (1) lowest symptom burden (n=101); (2) mixed symptom burden (n=93); and (3) highest symptom burden (n=57). Several demographic, mental health, and psychosocial factors significantly distinguished between subgroup membership. Results elucidate the heterogeneity in clinical presentations within these two overlapping conditions and suggest specific potential risk factors for experiencing greater symptom burden. Findings overall represent an important first step in identifying which older adults may benefit most from interventions for co-occurring chronic pain and cognitive concerns. PERSPECTIVE: This article characterizes distinct profiles of older adults with chronic pain and cognitive concerns and suggests potential risk factors for experiencing greater symptom burden. Findings can help inform which older adults are most likely to benefit from interventions targeting co-occurring chronic pain and cognitive concerns.

During childhood, children are presented with ample opportunities to learn about pain, including through their own experiences and interactions with others. Another possible source of influence is the media they consume. Portrayals of pain in children's television, movies and picture books have previously been examined; however, less is known about other mediums, like YouTube, that reach millions of children. This study aimed to investigate how pain-related events are portrayed in popular children's YouTube videos. Videos from 15 popular 'Made for Kids' YouTube channels (30 videos/channel) were screened for pain-related events. Channels were selected based on popularity (highest subscribers and views). Videos that included pain-related events were analysed using codes adapted from previous studies of pain in children's media. Pain-related events were commonly represented and present in 174 videos, with impact portrayals (i.e., where pain and or injury would be expected in real life, but no evidence of either was present) being the most frequent, followed by minor pain/injury. Boy characters experienced pain-related events more frequently than girl characters, but girls demonstrated more prosocial behaviours in response to sufferers than boys. Characters/presenters with racialized identities were underrepresented in pain-related events, yet racial stereotypes of violence were present. Findings of this study align with previous work investigating portrayals of pain in children's popular television, movies and picture books; demonstrating that sociocultural messaging about pain is consistent across different types of children's media. Future research should consider children's perspectives on pain-related events in popular children's media. PERSPECTIVE: This article describes the frequency and characteristics of pain-related events in popular 'Made for Kids' YouTube videos. Understanding the characteristics of this content is an essential step in understanding how pain may be socialised to children in their everyday media engagement.

Chronic back pain is embedded within close relationships, yet little is known about how partners' emotional and behavioral responses shape patients' daily pain experiences. This study examined whether partners' distress predicts their attempts to control (increase or decrease) the activity level of individuals with chronic back pain (ICBPs), and whether these responses are associated with worse subsequent pain outcomes the following day. One hundred forty-seven couples in which one partner had chronic back pain completed twice-daily electronic diary assessments for 30 days. The sample was older (70s), predominantly White, and well-educated. Partners reported daily pain-related distress and ICBPs reported partners' solicitousness (e.g., excessive help) and activity-related pressure. Multilevel models tested daily within- and between-couple associations and prospective next-day effects on pain severity, catastrophizing, and interference. As predicted, on days when partners experienced greater distress about ICBPs' pain, ICBPs reported more partner solicitousness (estimate =.234, SE =.037, p <.001; effect size =.799) and greater activity-related pressure (estimate =.033, SE =.017, p =.048; effect size =.524). In turn, greater partner solicitousness predicted higher pain catastrophizing (estimate =.050, SE =.021, p =.020; effect size =.098) and pain interference (estimate =.065, SE =.030, p =.028; effect size =.066) the following morning, controlling for prior-day pain outcomes. Contrary to prediction, activity-related pressure did not predict next-day pain severity, catastrophizing or interference. Partners' distress may contribute to behavioral responses in daily life, particularly excessive assistance, that inadvertently worsen pain-related functioning. PERSPECTIVE: Partners may experience emotional distress as a result of their loved one's pain. This distress may lead to behaviors that compromise the ability to cope effectively with pain. Findings highlight the interpersonal dynamics of chronic pain and suggest that interventions targeting partner distress and supportive behavior may improve pain self-management.

Shoulder pain limits function and increases healthcare costs. Resistance training is used, but the most effective approach for pain modulation remains unclear. Blood flow restriction (BFR) training combines low-load exercise with vascular occlusion demonstrating hypoalgesic effects across various disorders. However, evidence for non-specific shoulder pain (NSP) is limited. This study investigated the hypoalgesic effects of a single BFR session in NSP. In this randomized crossover trial, 48 participants with NSP were allocated to a BFR group (n = 24) or a sham-BFR group (n = 24). After a 7-day washout period, participants crossed over to the alternate condition. Each session consisted of low-load biceps curls with either BFR or sham-BFR, followed by a standardized shoulder exercise loading session. Outcomes included pressure pain thresholds (PPT), maximum voluntary isometric contraction (MVIC) of shoulder external rotation, and pain intensity (NPRS) during MVIC and abduction. BFR produced significantly greater increases in MVIC immediately after exercise (EMD = 0.058, p < 0.05) and following standardized shoulder exercise loading session (EMD = 0.042, p < 0.05) compared with sham-BFR. Both interventions reduced pain during external rotation MVIC and shoulder abduction, with larger reductions after BFR. Significant increases in PPT were found at the infraspinatus (EMD = 1.32, p < 0.05) and middle deltoid (EMD = 1.27, p < 0.05) only following BFR. A single low-load BFR session produced immediate, clinically meaningful reductions in pain and improvements in shoulder muscle strength in individuals with NSP, with benefits persisting after a standardized shoulder exercise loading session. Registered in ClinicalTrials.gov (NCT05956288) on 2023-07-21.

Trigeminal neuralgia (TN) patients frequently develop anxiety. We tested whether this anxiety reflects an independent dimension rather than a mere byproduct of chronic pain. We enrolled 58 TN patients-all with BNI grade V (treatment-refractory severe pain)-and 30 healthy controls. Evidence was assessed across three parallel dimensions: behavioral (HAMA anxiety levels), spatial (functional gradient architecture along the perceptual-cognitive axis, Gradient 3), and duration-related (Gradient 3 patterns with disease duration). Behaviorally, anxiety was elevated versus HC (HAMA: 9.23±6.11 vs 5.26±1.39, p=0.0006) but did not correlate with disease duration (r=-0.176, p=0.175). Spatially, Gradient 3 revealed a divergence (FDR-corrected q<0.05): the somatomotor network shifted toward the sensory pole (p=0.0028), while the limbic network shifted toward the cognitive pole (p=0.0017). Exploratory duration-related analyses showed a correlation between limbic network positioning and disease duration (r=-0.325, uncorrected p=0.013), with a trend-level early-stage association that warrants prospective validation. Pain and anxiety show divergent associations with disease duration in TN. These dissociations challenge the byproduct hypothesis and suggest that anxiety may warrant separate clinical consideration, though prospective validation is needed. PERSPECTIVE: This study identifies differing cortical network patterns in trigeminal neuralgia that may inform understanding of pain-anxiety comorbidity. The findings support further investigation of anxiety as a distinct clinical consideration, while duration-related associations remain exploratory and require longitudinal validation.

Fibromyalgia (FM) is a heterogeneous chronic condition with wide variability in symptom burden, psychosocial distress, and functional impact. This study aimed to identify latent FM subgroups reflecting multidimensional patient profiles using comprehensive biopsychosocial variables and model-based clustering methods within UK Biobank. Individuals meeting the 2016 American College of Rheumatology FM criteria (n = 4172) were analysed using Gaussian mixture clustering. Twenty-eight variables across sociodemographic, clinical symptoms, and psychological/behavioural domains were included. Cluster stability was evaluated using bootstrap resampling and adjusted Rand indices (ARI). Variable importance was assessed using Random Forest analysis. Three distinct subgroups were identified: the Resilient Majority (62.3%) with low symptoms and psychological resilience; the Severe Phenotype (20.1%) with pronounced pain, fatigue, and psychological distress; and the Socially Vulnerable Minority (17.6%) characterized by ethnic diversity, rural residence, and social isolation. Sociodemographic and psychological/behavioural variables (e.g. frequency of feeling down, home area population density, ethnicity, frequency of home visits, and smoking status) demonstrated greater discriminative contribution than clinical symptom variables. All clusters demonstrated high stability (ARI > 0.93). These findings identify subgroups within FM defined not only by symptom severity but also by structural vulnerabilities and psychosocial factors. Recognizing such heterogeneity has implications for developing stratified, equitable management approaches that integrate psychosocial dimensions alongside clinical symptoms. PERSPECTIVE: Three fibromyalgia subgroups were identified: a resilient majority, a severe phenotype with socioeconomic disadvantage, and a socially vulnerable minority characterized by ethnic diversity and rural isolation patterns. Psychosocial factors outperformed clinical symptoms in discriminating subgroups, underscoring the need for stratified and patient-centred management addressing the biopsychosocial complexity of fibromyalgia.

Chronic non-specific low back pain (CNSLBP) often coincides with alterations in postural behavior and respiration, which could contribute to pain complaints. Increasing evidence suggests that emotions are closely related to postural behavior and respiration. Thereby, emotions can affect symptom perception processes in CNSLBP. This quasi-experimental study examined how emotions affect symptom perception, postural behavior, and respiration in individuals with (n= 40) and without (n= 40) CNSLBP using script-driven emotional imagery. Participants imagined three auditory scripts describing states of relaxation, hostile-resistance, and acceptance, while standing upright on an unstable support surface with their eyes closed. During each trial, postural behavior was assessed by center of pressure (CoP) and trunk muscle electromyography (EMG), and respiration by end-tidal carbon dioxide (PetCO2). After each trial, participants self-reported bodily complaints. Emotion-induced differences in bodily complaints, CoP, EMG, and PetCO2 were compared between individuals with and without CNSLBP using mixed models. When compared to healthy individuals, those with CNSLBP reported more bodily complaints during the hostile-resistance (p<0.0001; t=5.18) and acceptance script (p=0.002, t=3.93). Moreover, individuals with CNSLBP reported more bodily complaints during the hostile-resistance script compared to the acceptance (p=0.01; t=3.44) and relaxation (p<0.0001; t=6.56) script. Emotional imagery did not affect CoP, EMG, or PetCO2 in either group (all p>0.05). While imagining emotional scripts did not result in alterations in postural behavior or respiration, it did alter perceived bodily complaints. This highlights the significance of symptom perception processes in individuals with CNSLBP. PERSPECTIVE: Our article provides innovative insights into the processes of symptom perception in individuals with chronic non-specific low back pain, as merely imagining an emotional script affects the perception of bodily complaints.

Temporal summation of pain (TSP) is a candidate phenotype marker of central pain facilitation, but variable test-retest reliability limits its clinical utility. This variability may arise from peripheral confounds in contact-based stimulation and from conflating facilitation probability with its magnitude. We evaluated whether contactless laser stimulation, which preferentially engages nociceptive afferents, enables reliable measurement of TSP by disaggregating these behavioral components. Twenty-seven healthy adults completed two identical visits separated by 1-2 weeks. Noxious laser stimulation was delivered in 30 triplet trials to the left dorsal hand. TSP was quantified using the following three complementary measures: (1) induction rate, defined as the proportion of triplets exhibiting facilitation; (2) conditional magnitude, defined as the mean proportional increase in pain when facilitation occurred; and (3) unconditional magnitude, defined as the mean proportional change across all triplets, regardless of whether facilitation occurred. Laser stimulation reliably induced temporal summation at the group level. No significant between-visit differences were detected in these measures. Single-measure and average-measure intraclass correlation coefficients were 0.49 and 0.65 for induction rate, 0.77 and 0.87 for conditional magnitude, and 0.65 and 0.79 for unconditional magnitude, respectively. Across blocks, overall pain intensity decreased, consistent with habituation, while induction rate showed no significant block effect and conditional magnitude showed block-related increases. These findings dissociate pain facilitation from global habituation and frame temporal summation as a composite behavioral process; isolating facilitation probability from magnitude may improve interpretability and support future mechanistic pain phenotyping. PERSPECTIVE: Contactless laser stimulation enables reliable measurement of temporal summation of pain by reducing contact-related peripheral confounds and dissociating facilitation occurrence from magnitude. These findings indicate that, at the behavioral level, temporal summation reflects separable probabilistic and amplification components, supporting its use for mechanistic pain phenotyping.