Stefan Elbers

129 Co-designing relapse prevention strategies throughout all phases, which promoted a solution-focused orientation for the participants. Alternatively, in EBCD, more emphasis is placed on ensuring that the collected patient experiences are received and understood by other stakeholders (e.g., by showing a film of patient interview segments that reflect key themes), before continuing to developing improvements (Donetto et al., 2015). These differences illustrate the versatility of co- design and its potential to adapt to different design environments. Strengths and Limitations The extensive documentation of the co-design activities allowed for a detailed reconstruction of the development process. Furthermore, during co-creation sessions, steering committee meetings, and the construction of the retrospective journey, representatives from all research groups were present, which resulted in a continuous integration of various perspectives during the project. However, we did not film or record any of the co-creation sessions. Although analyzing audio or video would have been time consuming, it would have provided further possibilities to observe stakeholder discussions during design activities and to include additional insights that we did not record. During the project, we experienced a tradeoff between validating the outcomes of co-design activities and analyzing the results for the next iteration. For example, an additional co- creation session during the “Define” phase with different stakeholders could have cross- validated the outcomes of the initial session. However, given limited resources, this would have resulted in fewer development iterations in the remaining period. A key argument in favor of more iterations is that quickly integrating stakeholder input into subsequent sessions directly visualizes the value of their input (Hinchcliff et al., 2014). However, a tendency towards more iterations increases the uncertainty to what extent the outcomes of this project can be generalized to the population (Seekins & White, 2013). Future Recommendations This study adds to the increasing number of initiatives that use co-design to structurally integrate contextual factors into the development of health care interventions (e.g. Jamin et al., 2018; O’Brien et al., 2016; Raynor et al., 2020; Revenäs et al., 2015), which help bridge the gap from development to actual implementation (Murray et al., 2010; Robert & Macdonald, 2017). When using co-design, it is important to relate the findings of the process to existing theories and treatments, for instance by using the behavior change technique taxonomy (Michie et al., 2013; Verbiest et al., 2019). This strengthens the co- design approach by combining stakeholder evaluations with existing theory. Importantly, further integration between co-design and theory-driven approach only becomes possible when using rigorous testing to evaluate the outcomes of the co-design process (Robert &