Stefan Elbers

30 Chapter 2 1991; Wilson, 2010; Wood & Neal, 2016). To understand the impact of these programmes on patients' ability to self-regulate their wellbeing after completion of the treatment programme, it is crucial to assess the change of IMPT outcomes over time. To acquire insight in both evidence-gaps, our first aim was to identify and analyse the change over time of key outcome measures in patients with chronic pain who participated in IMPT programmes. Therefore, the first research question is: How does the physical, psychological and social wellbeing of patients with chronic musculoskeletal pain who participated in IMPT programmes change over time? Our second aim was to explore the heterogeneity of study, patient, intervention and outcome characteristics: To what extent do cohorts vary with respect to study, patient and treatment characteristics? LITERATURE SEARCH METHODS Protocol and Registration The study was reported in line with the PRISMA guidelines (Moher et al., 2009; Moher et al., 2015) and the study protocol has been registered in PROSPERO under CRD42018076093. Search We performed our search in Medline and Embase via OVID, and PsycInfo and Cinahl via EBSCOhost from inception to May 2020. The search string was developed by experienced reviewers (SE and JK) and consisted of multiple blocks that were combined with Boolean operators (see Supplementary file 1). Each block included free text words as well as specific subject headings. In addition, we searched for grey literature including unpublished studies in the Dart Europe, Open access Theses and Dissertations, NDLTD, ClinicalTrials.gov and WHO ICTRP databases. For each included study we also performed forward (in Google Scholar) and backward reference searches. Eligibility Criteria Randomized controlled trials, as well as case series and cohort studies were included. Study cohorts had to include adult patients with chronic primary pain for at least 3 months that was primarily perceived in musculoskeletal structures (e.g. bones, joints, muscles or related soft tissues) (Treede et al., 2015). In case of mixed cohorts, at least 75% of the patients had to experience musculoskeletal pain. The criteria for IMPT programmes were based on the definition of Gatchel and colleagues and had to include (a) a common philosophy treatment in line with the biopsychosocial model of pain; (b) a treatment component where patients actively participated by means of tasks, training and/or exercise; (c) at least three different