Longitudinal invariance and information of the Depression, Anxiety, and Stress Scales.

Objectives: The study investigates the psychometric properties of the Depression, Anxiety, and Stress Scales (DASS-21).

Method: The DASS-21 was administered to a community sample twice over the course of 7 months (  = 235 and  = 171; 51% female, M  = 22 years). A partial credit Rasch model was used to determine the scales' longitudinal invariance and reliability.

Results: The DASS-21 mostly demonstrated longitudinal invariance across administrations. The Depression and Anxiety subscales were sufficiently reliable to distinguish among the suggested severity categories, but the Stress scale was not.

Conclusion: Several revisions of the DASS are recommended. It is also suggested that the Stress scale should be used with caution, given its low reliability.