Psychometric examination of the Multidimensional Psychological Flexibility Inventory Short Form (MPFI-24) and the Psy-Flex Spanish versions in individuals with chronic pain.

Background: Acceptance and Commitment Therapy (ACT) has been found to be beneficial for individuals dealing with chronic pain. The theoretical mechanisms of change proposed by ACT are based on the Hexaflex model. To comprehensively reflect this model, the Multidimensional Psychological Flexibility Inventory (MPFI) and Psy-Flex have been developed. The study aimed to adapt the MPFI-24 and the Psy-Flex for Spanish-speaking populations with chronic pain and to examine their dimensionality, internal consistency, convergent validity and incremental validity.

Methods: This cross-sectional study involved 309 Spanish-speaking adults with chronic pain who completed an online survey. The majority of the participants were women (88.3%). The ages ranged from 18 to 79 years.

Results: Factor analysis showed that the Spanish version of the MPFI-24 has 12 factors, consisting of six flexibility and six inflexibility factors, similar to the original version, but lacking second-order general factors. The Psy-Flex demonstrated a single-factor structure, maintaining the general factor of psychological flexibility seen in the original version. The MPFI-24 showed good internal consistency and adequate convergent validity, with the exception of the Acceptance and Experiential Avoidance subscales. The Psy-Flex showed good internal consistency and convergent validity. Notably, both the MPFI-24 and Psy-Flex scores significantly explained additional variance in psychological distress beyond other ACT-related measures of Hexaflex processes; however, only the Psy-Flex explained pain interference.

Conclusions: The Spanish adaptations of the MPFI-24 and Psy-Flex are valid and reliable instruments for assessing the Hexaflex model processes in Spanish-speaking adults with chronic pain.

Significance statement: Practitioners and researchers in chronic pain will find the Spanish versions of the MPFI-24 and the Psy-Flex here, along with recommendations for their use and scoring based on a robust psychometric rationale. It should be noted that these measures surpass the Chronic Pain Acceptance Questionnaire (CPAQ) and the Psychological Inflexibility in Pain Scale (PIPS), which are considered gold standards in chronic pain assessment.