Abstract
BACKGROUND: Despite decades of quality improvement efforts in mental healthcare, patient preferences remain insufficiently integrated into care planning and system design. Although person-centered care strives to align services with patients' most valued preferences, current tools for measuring those preferences often fall short. Embedding co-design approaches-where patients and other stakeholders collaborate as equal partners in tool development-is essential to ensure that measurement instruments are both relevant and resonant with lived experience. This study aimed to develop a questionnaire that captures patient preferences in mental healthcare through a co-design process that actively integrates lived experience, thereby enhancing face and content validity. METHODS: The development of the questionnaire followed four key phases: identification of domain, item generation, content validity, and pre-testing of questions. A co-design approach was integral to the entire process, with active collaboration with the co-researcher or co-designers at every phase. RESULTS: Nine themes were identified in the literature, and two novel themes, "the person as a whole" and "meaningful community connections" emerged through co-design and extend beyond prior studies. From 242 preliminary items, workshops refined the questionnaire to 58, and content validation further reduced it to 54 items with recommendations for clarity, simplicity, and anonymous responses. Pre-testing of questions confirmed the questionnaire's usability and face validity. CONCLUSIONS: This study demonstrates how traditional questionnaire development can be supported by co-design to effectively develop a patient preference questionnaire that is both valid and meaningful within the Danish mental healthcare context. While limitations exist, particularly regarding group dynamics and representation, the process sets a strong foundation for future work. PATIENT OR PUBLIC CONTRIBUTION: This study was co-designed in collaboration with individuals with lived experience of mental illness. A co-researcher with lived experience was involved throughout several stages of the research process, including the design and facilitation of workshops, recruitment of participants, and interpretation of findings. Additional 15 co-designers with lived experience were engaged in two workshops, contributing actively to the generation, refinement, and validation of questionnaire items. Their insights ensured that the tool reflects the values and preferences of those it aims to serve. Peer workers, clinicians, and researchers also supported the co-design process, helping facilitate workshops and integrate experiential and academic perspectives.