Psychological burden in nociplastic pain: Central Sensitivity as possible discriminating construct within different chronic pain conditions and healthy population

Background: Central Sensitivity (CS) is defined as an increased responsiveness of nociceptive neurons in the central nervous system to normal or subthreshold inputs. CS has been linked to the psychological burden associated with suffering from various chronic pain (CP) conditions, including fibromyalgia (FM) and chronic headache (CH). The present study aims to investigate whether CS can distinguish between CP conditions and healthy controls (HCs), as well as among different CP conditions, specifically CH, FM, and FM with CH. Methods: A total of 737 women (n=220 CH; n=200 FM; n=209 FM with CH; n=108 HCs) completed an online self-administered protocol consisting of the Central Sensitivity Inventory (CSI) and socio-anamnestic information. A general linear model ANCOVA was performed to test differences in CSI scores, covarying for sociodemographic variables showing a significant different distribution among groups (age, social and working status and educational level). Results: Data analysis showed a good fit for the model (R2 Adjusted=.407; df=7; F=73.172; p<.001) and a significant difference between groups in CSI scores (p<.001). The only covariate included in the model showing a significant effect was educational level (F= 32.208; p<.001). Post hoc tests using the Bonferroni method revealed that all clinical groups scored significantly higher than HCs (all p < .001). Additionally, FM with comorbid CH showed CSI scores significantly higher than all other clinical groups. Conclusions: CS appears to have a discriminating role among CP conditions, particularly in FM associated with CH. Including this dimension in the clinical evaluation of CP patients seems relevant to better understand the complex connection between CP and mental health.