Cortisol as a Marker of Pain and Distress Following Acute Musculoskeletal Trauma

Abstract

Objectives: The best available predictors of chronic pain development broadly encompass baseline metrics of cognition (i.e. beliefs/expectations) about the trauma and resulting symptoms. In the context of musculoskeletal trauma we have previously shown the Traumatic Injuries Distress Scale (TIDS) capable of risk stratifying cohorts for chronic pain development. Here we explore whether the physiologic marker cortisol shows meaningful associations with cognitions predictive of pain outcomes. Methods: Data for these cross-sectional analyses were drawn from an observational study that recruited 130 participants presenting to hospital with pain related to a recent non-catastrophic MSK trauma. Cortisol was measured from participant’s hair, saliva, and blood. In addition to pain and distress questionnaires, metadata such as age, sex, BMI, adverse childhood events, pre-trauma stress levels and pre-existing physical/psychological comorbidities were collected. Results: We found no significant associations between cortisol levels and pain or distress in isolation. When stratified by person-level variables, associations were revealed with distress (TIDS) in young age and low pre-trauma stress subgroups (hair cortisol) and low BMI (blood cortisol). Through hierarchical regression analysis we found the ‘cortisol X age’ or ‘cortisol X stress’ interaction terms significantly improved TIDS prediction beyond either variable in isolation (Age: ∆R2=15.1%; Pre-trauma stress: ∆R2=9.1%). Discussion: Our findings suggest that while linear correlations between pain-related distress and cortisol may be overly simplistic, certain person-level variables such as age, pre-trauma stress and BMI are worthy of consideration for experimental design or confounder characterization in future studies of pain and distress following musculoskeletal injuries especially when ‘trait’ (hair) cortisol is the predictor variable.