@Article{info:doi/10.2196/45334,
author="Kraska, Jake
and Bell, Karen
and Costello, Shane",
title="Graded Response Model Analysis and Computer Adaptive Test Simulation of the Depression Anxiety Stress Scale 21: Evaluation and Validation Study",
journal="J Med Internet Res",
year="2023",
month="Jun",
day="22",
volume="25",
pages="e45334",
keywords="graded response model; DASS-21; CAT; computer adaptive testing; simulation; psychological distress; depression; anxiety; stress; mental health; screening tool; tool; reliability; development; model",
abstract="Background: The Depression Anxiety Stress Scale 21 (DASS-21) is a mental health screening tool with conflicting studies regarding its factor structure. No studies have yet attempted to develop a computer adaptive test (CAT) version of it. Objective: This study calibrated items for, and simulated, a DASS-21 CAT using a nonclinical sample. Methods: An evaluation sample (n=580) was used to evaluate the DASS-21 scales via confirmatory factor analysis, Mokken analysis, and graded response modeling. A CAT was simulated with a validation sample (n=248) and a simulated sample (n=10,000) to confirm the generalizability of the model developed. Results: A bifactor model, also known as the ``quadripartite'' model (1 general factor with 3 specific factors) in the context of the DASS-21, displayed good fit. All scales displayed acceptable fit with the graded response model. Simulation of 3 unidimensional (depression, anxiety, and stress) CATs resulted in an average 17{\%} to 48{\%} reduction in items administered when a reliability of 0.80 was acceptable. Conclusions: This study clarifies previous conflicting findings regarding the DASS-21 factor structure and suggests that the quadripartite model for the DASS-21 items fits best. Item response theory modeling suggests that the items measure their respective constructs best between 0$\theta$ and 3$\theta$ (mild to moderate severity). ",
issn="1438-8871",
doi="10.2196/45334",
url="https://www.jmir.org/2023/1/e45334",
url="https://doi.org/10.2196/45334",
url="http://www.ncbi.nlm.nih.gov/pubmed/37347530"
}