Psychological flexibility and pain catastrophizing in endometriosis: Incremental validity and interaction effects in...

Psychological distress and reduced health-related quality of life are common among women with endometriosis, particularly when the condition is accompanied by chronic pain. Psychological flexibility (PF), a core process in Acceptance and Commitment Therapy, has emerged as protective in chronic pain, but it is unclear whether it adds explanatory power beyond pain intensity and pain catastrophizing or alters their impact in women with endometriosis. This study addressed these issues by (1) testing the incremental validity of PF in predicting psychological and functional outcomes after accounting for pain intensity and pain catastrophizing; and (2) examining whether PF moderates the association between catastrophizing and these outcomes.

A sample of 516 women with endometriosis (mean age 34.6 years, SD 6.28) was recruited through the Associazione Progetto Endometriosi ODV (APE) in Italy. Participants completed self-report measures of pain intensity, pain catastrophizing, PF, anxiety, depression, psychological well-being, and disability.

Hierarchical multiple regression analyses showed that pain catastrophizing explained an additional 14-18% of variance in outcomes beyond socio-demographic and pain variables, whereas PF accounted for further unique variance ranging from 3% for disability to 24-28% for anxiety, depression, and psychological well-being. Lower PF and higher catastrophizing were each independently associated with higher anxiety and depression, greater disability, and lower psychological well-being. There was no evidence for an interaction between catastrophizing and PF.

Overall, PF showed incremental validity over pain intensity and catastrophizing, and both PF and catastrophizing emerged as complementary interventions targets in women with endometriosis.