The purpose of the study was to explore aspects of implementing a SDM intervention including a digital decision tool for patients with severe mental illness in community psychiatry in Sweden.  A mixed method approach was used including both quantitative and qualitative methods. In designing the process evaluation and structuring the data of the intervention, we applied the process evaluation guide by Moore et al. (2015) including three identified evaluation components; Context, Implementation and Mechanism of impact.The results illustrates both facilitating factors and barriers in implementing SDM.  A facilitating factor was identified when staff collectively assumed that SDM was appropriate for formal decisions, such as care planning, assessments and planning at admission and discharge from a service.  Another facilitating factor was the use of the decision tool enabling an interactive communication between staff and user supporting the user to be informed and prepared in decisions.

A contextual barrier was a lack of a common agenda for increased patient participation in the units. SDM was a voluntary activity shaped by each staff member in accordance with his or her judgment, experience and attitude. Another barrier concerned decision making capacity in both staff and in users. In some care units staff felt that they did not have formal power regarding formulating and deciding upon interventions. Staff was also largely doubtful of patient's willingness and ability to participate in decisions. Confidence in patients' decision-making capacity and ability to integrate information was low.