Faulkner, Josh WSnell, Deborah LSiegert, RJ2025-04-162025-04-162024-10-07Brain Injury, ISSN: 0269-9052 (Print); 1362-301X (Online), Taylor and Francis Group, 39(2), 136-144. doi: 10.1080/02699052.2024.24112970269-90521362-301Xhttp://hdl.handle.net/10292/19095OBJECTIVE: In this study, we evaluated the psychometric properties of the Depression Anxiety Stress Scales 21 items (DASS-21) in a mild traumatic brain injury (mTBI) sample. METHOD: Treatment-seeking adults (n = 347) were recruited from outpatient rehabilitation services in New Zealand. Dimensionality, reliability, person separation index, and differential item functioning (DIF) of the DASS-21 were examined using Rasch analysis. RESULTS: Initial analysis of the complete 21-item DASS showed poor overall fit due to problems with individual items. Fit to the Rasch model was excellent when treated as three composite scores. The stress subscale demonstrated adequate model fit, dimensionality and good reliability. For anxiety, fit was not good, reliability was unsatisfactory and DIF was evident on one item. When this item was removed, fit to the model was still inadequate as was reliability. DIF was also evident for depression, but when this item was removed, fit to the model was adequate. CONCLUSION: The DASS-21 is a psychometrically sound measure of distress and stress for adults seeking treatment following mTBI. Ordinal to interval score conversion tables are provided to increase the precision of measurement. When assessing depression in a mTBI population, a 6-item depression subscale is recommended. Caution is advised in using the DASS-21 anxiety subscale alone.© 2024 The Author(s). Published with license by Taylor & Francis Group, LLC. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way. The terms on which this article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or with their consent.http://creativecommons.org/licenses/by-nc-nd/4.0/DASS-21mental healthMild traumatic brain injurypsychometricsRaschDASS-21Mild traumatic brain injuryRaschmental healthpsychometrics4201 Allied Health and Rehabilitation Science5203 Clinical and Health Psychology42 Health Sciences52 PsychologyMind and BodyBrain DisordersMental IllnessBehavioral and Social ScienceDepressionTraumatic Brain Injury (TBI)Physical Injury - Accidents and Adverse EffectsTraumatic Head and Spine InjuryNeurosciencesMental HealthMental health11 Medical and Health Sciences17 Psychology and Cognitive SciencesRehabilitation3202 Clinical sciences4201 Allied health and rehabilitation science5203 Clinical and health psychologyHumansMaleFemaleAdultPsychometricsReproducibility of ResultsMiddle AgedDepressionAnxietyYoung AdultPsychiatric Status Rating ScalesBrain ConcussionNew ZealandStress, PsychologicalAdolescentAgedHumansBrain ConcussionReproducibility of ResultsDepressionStress, PsychologicalAnxietyPsychiatric Status Rating ScalesPsychometricsAdolescentAdultAgedMiddle AgedNew ZealandFemaleMaleYoung AdultJournal ArticleOpenAccess10.1080/02699052.2024.2411297