Psychometric evaluation of the depression, anxiety, and stress scale-21 (DASS-21) among Chinese primary and middle school teachers

BACKGROUND: Teachers in high-stress roles face increasing psychological distress such as anxiety and depression, underscoring the need for validated assessment instruments. Given the current absence of a comprehensive, designated, and time-efficient scale capable of evaluating depression, anxiety, and stress among the teacher population, the Depression, Anxiety, and Stress Scale-21 (DASS-21) presents itself as a promising alternative. Despite the widespread application of the DASS-21 for assessing psychological distress across various populations, its validity among teachers, along with questions about its factor structure and its potential property of time equivalence, remain unverified. This study endeavors to address these considerations by investigating the psychometric properties of the DASS-21 specifically within the population of Chinese primary and middle school teachers. METHODS: Cross-sectional (n = 9,030) and longitudinal surveys (n = 1,642) were conducted using a non-probability sampling method. In addition to the DASS-21, the Chinese version of Chinese Teachers’ Job Burnout Questionnaire (CTJBO) was utilized to evaluate the criterion validity of this scale. Three different approaches, namely confirmatory factor analysis, Rasch analysis, and network analysis, were employed to evaluate internal reliability, construct validity, as well as time invariance of the DASS-21. RESULTS: The DASS-21 demonstrated a high degree of internal consistency (Cronbach’s α > 0.85) as well as excellent convergent validity, despite poor discriminant validity as determined by average variance extracted. Confirmatory factor analysis and network analysis further supported convergent validity. The three-factor structure outperformed one- and two-factor alternatives, establishing time invariance. Rasch analysis at the item level identified six inappropriate items within the anxiety and stress subscales, which were subsequently removed. Network analysis presented a better revised network. Regression analysis with emotional exhaustion as the criterion provided logical and accurate results. CONCLUSION: The DASS-21 was found to be a reliable and valid tool for measuring the mental health of teachers over time. To assess the instrument’s psychometric properties, a combination of confirmatory factor analysis, Rasch analysis, and network analysis was utilized, which proved effective and is recommended for evaluating contentious instruments. Based on the results of the study, researchers and healthcare professionals are recommended to use the DASS-21 for assessing teachers’ psychological distress. However, certain items identified in the study may need to be removed to enhance the instrument’s appropriateness for this specific population. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40359-023-01242-y.