Psychology, 2018, 9, 1095-1127 http://www.scirp.org/journal/psych ISSN Online: 2152-7199 ISSN Print: 2152-7180 DOI: 10.4236/psych.2018.95069 May 30, 2018 1095 Psychology Can the Depression Anxiety Stress Scales Short Be Shorter? Factor Structure and Measurement Invariance of DASS-21 and DASS-9 in a Greek, Non-Clinical Sample Theodoros A. Kyriazos, Anastassios Stalikas, Konstantina Prassa, Vasiliki Yotsidi Department of Psychology, Panteion University, Athens, Greece Abstract This study focused on the factor structure, invariance, reliability, and validity of two DASS versions: DASS-21 and DASS-9. Dimensionality was examined with Exploratory and Confirmatory factor analysis in 2271 Greek adults of the non-clinical population. Sample was split in three parts and the “3-faced con- struct validation method” was adopted. An EFA and a Bifactor EFA model were tested in the 20% subsample for both DASS-21 and DASS-9. Then, in the 40% subsample eleven CFA models were tested for DASS-21 and six for DASS-9 (using ICM-CFA, Bifactor CFA and ESEM). Optimal DASS-21 and DASS-9 models were successfully validated in the remaining 40% subsample (i.e. in a subsample of equal power). DASS-21 and DASS-9 showed strict measurement invariance across gender. Reliability (α and ω) and AVE con- vergent validity were adequate for both versions. Correlation analysis based on 10 different measures revealed a predominant uniform pattern of relations, similar for both versions. Considering all findings, the Greek versions of DASS-21 and DASS-9 are invariant, reliable and show construct and conver- gent validity. Keywords DASS-21, DASS-9 Factor Structure, 3-Faced Construct Validation Method, ESEM, ICM-CFA, Bifactor EFA, Bifactor CFA, Measurement Invariance, Greece, Normative Data 1. Introduction Depression is the most common psychological disorder across the globe (WHO, How to cite this paper: Kyriazos, T. A., Stalikas, A., Prassa, K., & Yotsidi, V. (2018). Can the Depression Anxiety Stress Scales Short Be Shorter? Factor Structure and Measurement Invariance of DASS-21 and DASS-9 in a Greek, Non-Clinical Sample. Psychology, 9, 1095-1127. https://doi.org/10.4236/psych.2018.95069 Received: April 1, 2018 Accepted: May 25, 2018 Published: May 30, 2018 Copyright © 2018 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access