Depression, anxiety, and stress continue to be among the largest burdens of disease, globally. The Depression, Anxiety, and Stress Scale-21 Items (DASS-21) is a shortened version of DASS-41 developed to measure these mental health conditions. The DASS-41 has strong evidence of validity and reliability in multiple contexts. However, the DASS-21, and the resulting item properties, has been explored less in terms of modern test theories. One such theory is Item Response Theory (IRT), and we use IRT models to explore latent item and person traits of each DASS-21 sub-scale among people living in Malaysia. Specifically, we aimed to assess Classical Test Theory and IRT properties including dimensionality, internal consistency (reliability), and item-level properties. We conducted a web-based cross-sectional study and sent link-based questionnaires to people aged 18 and above in a private university and requested to roll out the link. Overall and individual sub-scales’ Cronbach’s alpha of the DASS-21 indicates an excellent internal consistency. The average inter-item correlation and corrected inter-item correlations for each of the sub-scales indicated acceptable discrimination. On average, DASS-21 total scores and sub-scale scores were significantly higher among female participants than males. The Graded Response Model had better empirical fit to sub-scale response data. Raw summated and latent (IRT estimated) scores of the Depression, Anxiety, and Stress sub-scales, and overall DASS-21 were strongly correlated. Thus, this study provides evidence of validity supporting the use of the DASS-21 as a mental health screening tool among Malaysians. Specifically, standard error of measurement was minimized to provide robust evidence of potential utility in identifying participants who are and are not experiencing these mental health issues. Additional research is warranted to ensure that test content culturally appropriate and accurately measuring cultural norms of depression, anxiety, and stress.

抑郁、焦虑和压力仍然是全球最大的疾病负担之一。抑郁、焦虑和压力量表 21 项目 (DASS-21) 是 DASS-41 的缩短版本，旨在测量这些心理健康状况。DASS-41 在多种情况下具有强有力的有效性和可靠性证据。然而，DASS-21 以及由此产生的项目属性在现代测试理论方面的探索较少。一个这样的理论是项目反应理论 (IRT)，我们使用 IRT 模型来探索马来西亚人民中每个 DASS-21 子量表的潜在项目和个人特征。具体来说，我们旨在评估经典测试理论和 IRT 属性，包括维度、内部一致性（可靠性）和项目级属性。我们进行了一项基于网络的横断面研究，并向一所私立大学的 18 岁及以上的人发送了基于链接的调查问卷，并要求推出该链接。DASS-21 的总体和单个子量表的 Cronbach's alpha 表明具有出色的内部一致性。每个子量表的平均项目间相关性和校正的项目间相关性表明可以接受的歧视。平均而言，女性参与者的 DASS-21 总分和子量表得分显着高于男性。分级响应模型对子尺度响应数据具有更好的经验拟合。抑郁、焦虑和压力子量表的原始总和和潜在（IRT 估计）得分与整体 DASS-21 密切相关。因此，这项研究提供了支持使用 DASS-21 作为马来西亚人心理健康筛查工具的有效性证据。具体来说，测量的标准误差被最小化，以提供强有力的证据证明在识别正在经历和没有经历这些心理健康问题的参与者方面的潜在效用。有必要进行进一步的研究，以确保测试内容在文化上适当，并准确衡量抑郁、焦虑和压力的文化规范。