Psychosocial Processes in Endometriosis-Related Pain: The Role of Interpretation Bias and Implications for a Biopsychosocial Approach

Abstract

Endometriosis is a chronic, progressive condition affecting approximately 10% of individuals born with a uterus worldwide. Pain is the most common and most impactful symptom. Biomedical treatments for endometriosis-related pain have limited efficacy and there is a weak relationship between anatomical severity and pain, indicating the involvement of psychosocial factors. Yet, such factors remain understudied. This thesis therefore investigates psychosocial mechanisms involved in endometriosis-related pain and its treatment. Chapter 1 is an overview of endometriosis-related pain. Chapter 2 presents the first biopsychosocial model of endometriosis-related pain. The COmprehensive Model of endometriosis-related Pain encompassing Agency, Sense making and Systemic factors (COMPASS model) describes psychosocial factors associated with less pain distress and interference, even with high pain severity. Chapter 3 showed that interpretation bias, a process posited in the COMPASS model and the leading psychological model of chronic pain, was elevated among individuals with painful endometriosis compared to healthy controls and uniquely associated with pelvic pain interference. Chapter 4 presents the Pelvic Pain Bias Assessment, a pelvic pain specific interpretation bias with 27 ambiguous scenarios that differentiate individuals with endometriosis, adenomyosis and chronic pelvic pain from individuals without any pain related conditions. Stronger interpretation bias was related to more severe pelvic pain and menstrual symptom severity. Chapter 5 adapted this task to investigate whether interpretation bias could be modified for therapeutic benefit through Cognitive Bias Modification for Interpretation (CBM-I). No differences in interpretation bias between the treatment and placebo conditions were evident post intervention, indicating a null trial. Chapter 6 discusses the broader theoretical and clinical implications of this program of research and avenues for future research.