Capturing daily well-being: psychometric evaluation of the MHC-SF in a daily diary design.

Research on well-being has predominantly relied on cross-sectional retrospective person-level assessments, which may overlook short-term fluctuations across contexts and time. The present study evaluated a daily diary adaptation of the Mental Health Continuum-Short Form (MHC-SF) in a 14-day experience sampling design comprising 13 end-of-day assessments followed by a final questionnaire on day 14 in a German-speaking sample (N = 262). The retrospective two-week MHC-SF and the daily adaptation of the MHC-SF were examined using traditional psychometric approaches (internal consistency, confirmatory factor analysis) and advanced methods (generalizability theory, multilevel reliability, multilevel confirmatory factor analysis, and exploratory structural equation modelling). Results provided preliminary and qualified support for the daily diary adaptation of the MHC-SF. Evidence was strongest for the total MHC score and emotional well-being, which showed comparatively greater within-person variability and acceptable within-person reliability. In contrast, psychological and especially social well-being showed higher between-person stability and weaker evidence for capturing short-term daily fluctuations. The retrospective two-week MHC-SF showed excellent internal consistency, but its factor structure was not well captured by restrictive CFA models. ESEM provided better global fit, although the loading pattern suggested a dominant general well-being factor and limited empirical separation of the three domains, particularly for social well-being items. Subsequent lagged analyses indicated moderate day-to-day stability of well-being. Overall, these results support the utility of the MHC-SF for assessing overall and emotional aspects of daily well-being in ecologically valid settings, whereas psychological and particularly social well-being should be interpreted more cautiously and may require further adaptation for intensive longitudinal designs.