Background: The aim of this study was to develop and evaluate psychometric properties of the Clinical Decision Making Style (CDMS) scale which measures general preferences for decision making as well as preferences regarding the provision of information to the patient from the perspectives of people with severe mental illness and staff.
Methods: A participatory approach was chosen for instrument development which followed 10 sequential steps proposed in a current guideline of good practice for the translation and cultural adaptation of measures. Following item analysis, reliability, validity, and long-term stability of the CDMS were examined using Spearman correlations in a sample of 588 people with severe mental illness and 213 mental health professionals in 6 European countries (Germany, UK, Italy, Denmark, Hungary, and Switzerland).
Results: In both patient and staff versions, the two CDMS subscales "Participation in Decision Making" and "Information" reliably measure distinct characteristics of decision making. Validity could be demonstrated to some extent, but needs further investigation.
Conclusions: Together with two other five-language patient- and staff-rated measures developed in the CEDAR study (ISRCTN75841675) - "Clinical Decision Making in Routine Care" and "Clinical Decision Making Involvement and Satisfaction" - the CDMS allows empirical investigation of the complex relation between clinical decision making and outcome in the treatment of people with severe mental illness across Europe.