Comprehensive and Efficient Assessment of Psychological Flexibility in the Context of Chronic Pain

Background: The Multidimensional Psychological Flexibility Inventory (MPFI) is a measure of all facets of psychological flexibility and inflexibility, potentially important processes of change in psychological treatment for chronic pain. In some contexts, it can be considered too long. The aim of this study was, therefore, to validate a short form MPFI (MPFI-24P) in a chronic pain sample.

Methods: Adults with chronic pain were recruited online (N = 404) for a cross-sectional survey study. They first completed pain background questions and the MPFI. For examining convergent construct validity and explained variance in pain-related outcomes, participants also completed the Brief Pain Inventory (BPI) Pain Interference Scale, the Work and Social Adjustment Scale (WSAS) and the Patient Health Questionnaire (PHQ-9), a depression measure. Data were collected on two occasions, 2 weeks apart. Item response theory (IRT) and confirmatory factor analysis (CFA) were used for selecting the best-performing items.

Results: IRT parameters were overall adequate, and hierarchical CFA demonstrated a good model fit. Network analysis of the MPFI items indicated that, in general, items intended to measure the same facets were substantially interconnected, more so for the inflexibility items. Temporal stability was adequate, and internal consistency was good. The MPFI-24P correlated with pain interference, work and social adjustment and depression, with the inflexibility scale better predicting these outcomes. The MPFI-24P correlated strongly with the full-length MPFI.

Conclusions: The MPFI-24P for chronic pain is generally valid and reliable, especially the inflexibility scale. It performs similarly to the full-length MPFI.

Significance: This paper contributes with a measure that is both feasible to use in clinical practice and research, while being able to measure all facets of psychological flexibility and inflexibility-psychological processes of change that are important to evaluate in psychological treatment of chronic pain in order to better individualize treatment.