An experimental and clinical investigation of psychological and neural factors associated with individual differences in pain and pain modulation

Abstract

Chronic pain is a multi-faceted condition comprising of pathological, psychological and biological influences. This poses a significant problem to accurate assessment and treatment, with symptomology commonly not matching pathology. It is also unclear why some individuals develop chronic pain, while others appear resilient. Identifying individual differences in pain processing and modulation may be one method to help identify individuals who are susceptible to pain. Consequently, this thesis examined pain, its assessment and management in a clinical setting and individual differences in pain response in a laboratory setting. Study one evaluated pain ratings from hysteroscopy patients, to understand the prevalence of pain. Clinician estimates of pain were used to examine the accuracy of clinical pain assessment and how this related to pain management. Despite being considered a minimally-painful procedure, we found that patients’ pain ratings varied substantially, and were inversely correlated with clinician estimates. Our results indicate that hysteroscopy should not be advertised as a minimally-painful procedure. Advancing pre-surgical assessments to predict individuals at risk of developing pain could have important clinical implications. Individual differences in pain behaviour and response were examined in studies two and three, using resting-state connectivity in healthy controls. Study 2 investigated dispositional mindfulness, alongside sensory and cognitive pain variables. Trait mindfulness was associated with beneficial pain responses. Mindfulness was also associated with higher functional connectivity to the somatosensory cortex, and lower connectivity to the prefrontal cortex, with a precuneus seed. Our results may suggest that trait mindfulness is associated with increased sensory, present-moment focus, facilitating more effective pain management. Study 3 investigated Conditioned Pain Modulation (CPM), which quantifies the efficiency of descending modulation circuitry. Our results indicate that high CPM is associated with increased connectivity between pain modulatory and processing regions. Taken together, this research suggests that clinical assessments may benefit from psychometrics quantifying individual differences in their intrinsic ability to manage pain, to detect patients vulnerable to pain.