Stefan Elbers

223 Summary SUMMARY Chronic pain is one of the leading causes of worldwide disability. Unfortunately, there is often no treatment option available that directly influences the pain itself. Instead, biopsychosocial approaches that aim to decrease disability and optimize self-management, wellbeing and daily life functioning are considered treatments of choice. Since their introduction in the 1950s, the so-called InterdisciplinaryMultimodal PainTreatment (IMPT) programmes have become increasingly popular and spread globally. The programmes are provided by a team of health care providers with different professional backgrounds who continuously collaborate to deliver comprehensive biopsychosocial treatment. Despite evidence that IMPTprogrammes have a positive effect onphysical,mental and social health outcomes, there are indications that patients find it difficult to maintain positive treatment gains over time. This doctoral thesis is centred around this potential problem of relapse after successful treatment. The first part focuses on obtaining and maintaining an up-to-date overview of the current state of research literature on longitudinal outcomes of IMPT programmes. In Chapters 2 and 3 , we address the following questions: 1. How does the physical, psychological and social health of patients with chronic pain who participated in IMPT programmes change over time? 2. To what extent do the included studies vary with respect to study design, patient and treatment characteristics? 3. How can we transform a regular review into a living systematic review to increase the speed of dissemination and implementation of scientific findings into clinical practice? In Chapter 2 , we describe the results of a systematic review and meta-analysis. The two main objectives of this study were a) to analyse the longitudinal outcomes of patient cohorts who participated in IMPT programmes and b) to describe the variation of study, patient, treatment and outcome characteristics in detail.We identified 65 eligible studies describing the change over time of 74 unique patient cohorts. For all these cohorts, there was at least one pre-treatment and a one-year post-treatment measurement on one of the outcomes of interest (i.e. pain interference, physical functioning, depression, anxiety, anger, emotional functioning, self-efficacy, social functioning, and pain intensity). We evaluated change over time by calculating contrasts between pre-post, post-final follow-up and pre-final follow- up measurements. Most of the pre-post contrasts (85%) showed a statistically significant favourable change over time. Importantly, in the majority of these cohorts, this effect was maintained over time or even improved at final follow-up. This indicates that participation in IMPT programmes is associated with positive changes in health outcomes, which are generally maintained at follow-up. When interpreting these findings, it is important to