STructured lifestyle education for people WIth SchizophrEnia (STEPWISE): mixed methods process evaluation of a group-based lifestyle education programme to support weight loss in people with schizophrenia

STEPWISE is a theory-informed self-management education programme that was co-produced with service users, healthcare professionals and interventionists to support weight loss for people with schizophrenia. We report the process evaluation to inform understanding about the intervention and its effectiveness in a randomised controlled trial (RCT) that evaluated its efficacy. Following the UK Medical Research Council (MRC) Guidelines for developing and evaluating complex interventions, we explored implementation quality. We considered causal mechanisms, unanticipated consequences and contextual factors associated with variation in actual and intended outcomes, and integrated treatment fidelity, using the programme theory and a pipeline logic model. We followed a modified version of Linnan and Steckler's framework and single case design. Qualitative data from semi-structured telephone interviews with service-users (n = 24), healthcare professionals delivering the intervention (n = 20) and interventionists (n = 7) were triangulated with quantitative process and RCT outcome data and with observations by interventionists, to examine convergence within logic model components. Training and course materials were available although lacked co-ordination in some trusts. Healthcare professionals gained knowledge and some contemplated changing their practice to reflect the (facilitative) 'style' of delivery. They were often responsible for administrative activities increasing the burden of delivery. Healthcare professionals recognised the need to address antipsychotic-induced weight gain and reported potential value from the intervention (subject to the RCT results). However, some doubted senior management commitment and sustainability post-trial. Service-users found the intervention highly acceptable, especially being in a group of people with similar experiences. Service-users perceived weight loss and lifestyle benefits; however, session attendance varied with 23% (n = 47) attending all group-sessions and 17% (n = 36) attending none. Service-users who lost weight wanted closer monitoring and many healthcare professionals wanted to monitor outcomes (e.g. weight) but it was outside the intervention design. No clinical or cost benefit was demonstrated from the intermediate outcomes (RCT) and any changes in RCT outcomes were not due to the intervention. This process evaluation provides a greater understanding of why STEPWISE was unsuccessful in promoting weight loss duri