Longitudinal measurement invariance and psychometric properties of the Overall Anxiety Severity and Impairment Scale (OASIS), Overall Depression Severity and Impairment Scale (ODSIS), and Positive Emotion Scale (PES) among community-dwelling adults.

= 84) also participated in a 1-month longitudinal follow-up, completing the OASIS, ODSIS, and PES weekly across four time points. Both confirmatory bifactor analyses and exploratory graph analysis results supported the essential unidimensionality and dissociability of the OASIS, ODSIS, and PES items. Convergent validity coefficient values for all three measures were positive, significant, and large and were significantly greater than all discriminant validity coefficients. Longitudinal invariance model results indicated that the OASIS, ODSIS, and PES scores maintained stable measurement properties across four weekly assessments. Overall, these findings extend the existing literature, providing the first evidence of the dissociability of the OASIS, ODSIS, and PES dimensions, their basic measurement properties, and the longitudinal measurement invariance of their scores, at least among community-dwelling adults. (PsycInfo Database Record (c) 2026 APA, all rights reserved).