OBJECTIVE: This study aimed to examine the validity of the Arabic version of the Depression Anxiety Stress Scale-21 (DASS-21) in 149 illicit drug users. METHODS: We calculated alpha coefficient, inter-item and item-total correlations, coefficients of reproducibility and scalability (CR and CS), item difficulty and discrimination indices. RESULTS: The DASS-21 had an acceptable reliability; but values of the CR and the CS were less than acceptable. Items varied in difficulty and discrimination; some items are candidates for elimination. CONCLUSION: The DASS-21 is a probabilistic and not a deterministic measure of distress; it has problematic items and needs further investigations.

Ali, A. M., et al. (2017). "The Arabic Version of The Depression Anxiety Stress Scale-21: Cumulative scaling and discriminant-validation testing." Asian J Psychiatr 30: 56-58.

https://www.ncbi.nlm.nih.gov/pubmed/28755630