Heterogeneity in the experience of chronic pain: unravelling the biopsychosocial context and the quantification of treatment success

The primary objective of the present thesis was to unravel the heterogeneity of the pain experienced by chronic pain patients that was recorded on patient-reported outcome measures (PROM’s). This was analyzed by both using cross-sectional and longitudinal study designs. When observing sex differences in fear avoidance, we have found that men have higher scores of fear avoidance on average, yet their scores are not related to pain intensity, while the contrary happens in women: when fear avoidance increases, so does pain intensity. Moreover, this thesis specifies that within the chronic pain population the more vulnerable populations, like the low educated and unemployed, have a more severe pain experience than the overall chronic pain population. The clinical implication of these findings are of great importance, as these vulnerable groups may experience greater difficulties in accessing and understanding information about pain, yet as well in self-management, making health decisions and the use of the health care system, due to presence of low health literacy. In clinical practice and in pain management, attention needs to be given to this bottleneck as it can hinder treatment success. Furthermore, this thesis shows that the pain reduction necessary to be satisfactory about an intervention varies according to study design and baseline pain intensity. Thus, it is difficult to generalize at what amount of pain relief a patient with chronic pain is satisfied with, and thus when ran intervention can be labelled as successful.