Exploring the relationship between pain intensity and psychological distress: a parallel mediator, cross-sectional, registry study of >6,400 patients in Sweden.

OBJECTIVES

Chronic pain is associated with an increased prevalence of anxiety and depression. However, correlations between pain intensity and psychological distress are generally weak, suggesting a more complex relationship. Although evidence indicates a bidirectional association, the role of potential mediators warrants further study. The aim of this cross-sectional registry study was to explore mediators of the relationship between pain intensity and psychological distress, and vice versa, among individuals with chronic pain.

METHODS

This cross-sectional cohort study included 6,497 adult chronic non-cancer pain patients from the Swedish Quality Registry for Pain Rehabilitation (SQRP) with Patient-Reported Outcome Measures (PROMs) data (2008-2016). Five potential mediators - catastrophizing, fear-avoidance, physical activity level, acceptance and insomnia - were examined in the bidirectional relationship between pain intensity and psychological distress using Partial Least Squares Structural Equation Modelling (PLS-SEM).

RESULTS

The direct paths (i.e., correlations) between pain intensity and psychological distress in both directions became non-significant when controlling for the five mediators. Insomnia and catastrophizing emerged as the most important mediators, each with medium effect sizes, followed by acceptance, which showed a small effect size. Fear-avoidance demonstrated little to no influence. Physical activity showed no substantial mediating effect in any model.

CONCLUSIONS

This study supports the idea that the clinically observed association between pain intensity and psychological distress is more accurately explained by the influence of mediators, specifically catastrophizing, insomnia, and acceptance, rather than a direct effect between the two. These findings suggest that clinical assessments and interventions for patients with chronic pain should prioritize addressing catastrophizing, insomnia, and acceptance.