Methodological Challenges in Treatment Mediation Analysis: Examples from Studies Targeting Psychological Factors in Patients with Musculoskeletal Pain

This PhD project was nested within the Psychological Workstream of the Spinal Pain Programme,a National Institute for Health Research (NIHR) funded programme of work (Grant code RPPG-0707-10131) obtained at the Research Institute for Primary Care and Health Sciences by Elaine Hay and colleagues. The idea for this project was devised following discussion of the development of an intervention to target illness perceptions to improve functional outcomes for patients with low back pain. Previous Research Institute work had focused on prognostic studies and evidence had been gathered on what factors influenced patient outcome, but little work had been carried out to investigate whether these same factors could also be effectively targeted during treatment. This PhD project was devised to address this gap in knowledge. Throughout the course of this PhD project I have developed the ideas in this thesis under the guidance of my supervisors (Jonathan Hill, Daniëlle van der Windt and Chris Main (Chris took over from Kevin Vowles, who supervised me until August 2012)). My supervisors advised on the planning of all the analyses presented and on the writing and structure of the included chapters. I designed the analysis plans, conducted all analyses and wrote all chapters. I received guidance on search strategies from Joanne Jordan and Nadia Corp (Chapter 4), and the critical appraisal of the studies included in Chapter 4 was aided by Jemma Cowen. Elaine Thomas provided statistical guidance on Chapters 5 and 6 and Kelvin Jordan and Anne Smith provided guidance on the Latent Growth Modelling presented in Chapter 7. All of the data presented in this thesis was collected prior to my appointment at the Research Institute. I was provided with cleaned datasets from Nadine Foster (BeBACK data presented in Chapter 5), Jonathan Hill (STarT Back data presented in Chapter 6) and Michael Von Korff (Back In Action data presented in Chapter 7). Data from the IMPACT service (Chapter 8) was provided by Julie Ashworth, which did require cleaning by myself prior to use