Stefan Elbers

106 Chapter 4 weights are included in the calculation of the overall effect. Visual inspection of the forest plots showed that only few individual studies reported small but statistically-significant effects, indicating that other forms of synthesis probably would have yielded similar interpretations. A second limitation is that our conclusions relate to average group effects and do not provide more detailed information on the proportion of patients that respond well to self-management interventions. Although a responder analysis is recommended (Henschke et al., 2014), very few studies provided such details. The consequence is that we were unable to explore beyond an average effect at study level. Furthermore,weaimed toexpose thevariousmechanismsof self-management interventions by identifying and classifying the behaviour change strategies as much as possible. This method revealed commonly used strategies (e.g. a focus on goals and planning) as well as variation in the selection of techniques to support adaptive behaviour change for patients with chronic pain. This approach opened the black box of self-management interventions to a certain extent. Although it seemed a logical next step to investigate whether specific combinations of BCTs influence the outcomes (e.g. Michie et al., 2009), we refrained from doing these analyses. Due to the generally small standardized mean differences throughout the comparisons (range SMD between studies = −1 to 0.41), we hypothesized that further exploration would not yield meaningful information. CONCLUSION There ismoderate quality evidence that generic self-management interventions have a small clinically unimportant post-intervention effect on physical function and pain intensity. For physical activity, there is low quality evidence for no post-intervention effect and for self- efficacy, though we identified a trend favouring self-management interventions. At follow- up, there is moderate quality evidence for no effect of self-management interventions on physical function and pain, and low quality evidence for no effect on physical activity. In addition, we found a small but clinically unimportant long-term effect for self-management interventions on self-efficacy. Overall, these findings indicate that self-management interventions only have a marginal benefit on self-efficacy, pain intensity, physical function, and physical activity for patients with chronic musculoskeletal pain. Acknowledgements We acknowledge the support of Jurgen Mollema MSc from the University of Applied Sciences Utrecht with constructing the search string and performing the literature search. Issues concerning statistical analyses were discussed with Cas Kruitwagen, MSc from the Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht. We