Pain medicine basics: Overview

The Journal of Pain invites contributions for a special issue focusing on pain disparities, particularly among underrepresented and/or marginalized populations. This call aims to explore the unique challenges, burdens, and resilience factors experienced by these populations. We welcome submissions from scholars of diverse and underrepresented backgrounds and from individuals with lived experiences. Topics of interest include explanatory mechanisms of pain disparities, intersectional approaches, interventions to reduce disparities, resilience factors, new frameworks, emerging technologies, underrepresented populations, recruitment methods, and basic science studies. The goal is to encourage research that explains and addresses pain disparities, moving beyond mere documentation of group differences.
Guest Editors:
Emily J. Bartley
Mary Janevic
Martha Kenney

Abstract
Dysmenorrhea is menstrual pain of uterine origin that can be classified as primary (PD) or secondary (SD). The worldwide prevalence of dysmenorrhea has been estimated in previous systematic reviews; however, these results are often limited by the focus on specific populations, or the inclusion of studies published only in English. Therefore, we estimated the worldwide prevalence of dysmenorrhea of both PD and SD. In this systematic review, we searched 6 databases for studies reporting the prevalence of dysmenorrhea published between 2000 and 2024, without language restriction. The risk of bias of the included studies was assessed using the Joana Briggs Institute tool. Meta-analysis was conducted in Rstudio. The heterogeneity within meta-analyses was evaluated by I2 statistics. Subgroup analyses were performed by PD, SD, age group, and study setting to investigate sources of heterogeneity as well. The certainty of evidence was assessed using GRADE modified for prevalence studies. A total of 336 studies were included in this systematic review. Most of them were conducted in Asia (49.4%). The pooled worldwide prevalence of dysmenorrhea, PD, and SD were 71.3% (95% CI 68.7%-73.8%), 73% (95% CI 68%-78%), and 35% (95% CI 19%-56%), respectively. Dysmenorrhea was more prevalent in Central America (89.6%), Sri Lanka (97.7%), among adults (73.3%), and at universities (78.4%). All subgroup analyses showed high heterogeneity (I2 = 99.5%-100%) with very low certainty of evidence. This high prevalence of dysmenorrhea worldwide highlights the need for healthcare providers and public health organizations to address menstrual pain's global burden.

Abstract
Objectives: Although significant progress has been made in recent years in the field of pain modulation, information regarding patients' pain modulation profiles remains largely research-bound and is not yet easily accessible in clinical settings. The aim of this study was to develop and validate a model for estimating pain modulation profiles - including temporal summation of pain (TSP) and conditioned pain modulation (CPM) - using easily accessible measures.

Methods: This study included 347 pain-free individuals and 108 with chronic pain. TSP was induced via tonic heat pain stimulations, while CPM was evaluated using pressure pain thresholds (CPM-PPT) and tonic heat pain stimulations (CPM-HPS) as test stimuli, with the cold pressor test as the conditioning stimulus. Independent variables included demographic, psychological, and physiological measures. A LASSO regression with cross-validation was used to identify key independent.

Results: For TSP, the model explained 40% of the variance, incorporating factors such as monoamines and blood pressure. For CPM, the CPM-HPS model performed best, accounting for 35% of the variance, with blood pressure, sex and pain catastrophizing identified as important predictors.

Discussion: Overall, these results indicate that TSP and CPM can be partially estimated using readily accessible measures, but high prediction error currently limits their clinical applicability.

Abstract
Differences in pain responses between adults with or without psychiatric conditions are documented, yet the certainty of evidence on the topic has not been assessed. We examined pain responses to experimentally induced pain in individuals diagnosed with anxiety or depressive disorders compared to controls without mental health conditions. We also explored the influence of pain modality and associations between pain perception and symptoms severity. PubMed, CINAHL, PsycINFO, Cochrane, and Embase were searched from inception to March 2025. Included studies reported pain measures (pain threshold, intensity, tolerance, unpleasantness) in adults with anxiety or depression, without co-occurring chronic pain, and healthy controls. The JBI Checklist for Analytical Cross-Sectional Studies and the Quality in Prognosis Studies assessed risk of bias. Certainty of evidence was judged by the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) approach. Twenty-eight studies (1460 participants, 935 females) were included, most presenting moderate to high risk of bias. Compared to controls, individuals with depression exhibit higher pain thresholds [SMD = -.30 (95% CI -.60, -.01)] and pain intensity [SMD = .47 (95% CI .08, .86)], while those with anxiety exhibit lower pain thresholds [SMD = -.39 (95% CI -.61, -.17)] (GRADE: very low for all outcomes). Results differed depending on pain modality. Pain threshold was moderately correlated with depression severity: r = .437 (95% CI .208, .621). The data suggest distinct altered pain perception patterns, characterized by higher pain thresholds in depression and lower pain thresholds in anxiety. Adults with depression may be particularly sensitive, but not restricted to, ischemic stimuli. REGISTRATION: OSF (doi:10.17605/OSF.IO/U453J). PERSPECTIVE: This systematic review assessed how pain perception patterns may differ in individuals with anxiety or depression. Few studies included participants with anxiety, controlled for comorbidities, or were recently conducted, thus caution is needed before interpreting our findings. This underscores the need for updated and methodologically robust research on this field.