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Open AccessArticle

Factorial Structure and Validity of Depression (PHQ-9) and Anxiety (GAD-7) Scales after Traumatic Brain Injury

The Department of Social Psychology, Helmut Schmidt University, 22043 Hamburg, Germany
The Institute of Medical Psychology and Medical Sociology, Georg August University, 37073 Göttingen, Germany
Department of Public Health, Erasmus University Medical Center, 3000 Rotterdam, The Netherlands
Institute of Medical Statistics, Medical Center, Georg August University, 37073 Göttingen, Germany
Division of Anaesthesia, University of Cambridge/Addenbrooke’s Hospital, Box 157, Cambridge CB2 0QQ, UK
Author to whom correspondence should be addressed.
For the list of CENTER-TBI Investigators and Participants, see the Supplementary Material.
J. Clin. Med. 2020, 9(3), 873;
Received: 11 February 2020 / Revised: 10 March 2020 / Accepted: 11 March 2020 / Published: 23 March 2020
(This article belongs to the Section Psychiatry)
Background: The dimensionality of depression and anxiety instruments have recently been a source of controversy. Objectives and Design: In a European-wide sample of patients after Traumatic Brain Injury (TBI), we aim to examine the factorial structure, validity, and association of the Patient Health Questionnaire for depression (PHQ-9) and the Generalized Anxiety Disorder (GAD-7) instruments. This study is based on longitudinal observational data. We conducted analyses of factorial structure and discriminant validity of outcomes six-months after TBI. We also examined the prevalence, co-occurrence, and changes of scores on the PHQ-9 and GAD-7 at 3-, 6-, and 12-month post-TBI assessments. Participants: At six-months post-TBI assessment, 2137 (738 (34.5%) women) participants completed the PHQ-9 and GAD-7 questionnaires. For the longitudinal analysis, we had 1922 participants (672 (35.0%) women). Results: The results of exploratory factor analysis suggested a general latent construct underlying both PHQ-9 and GAD-7 measures. Confirmatory factor analyses showed a slight improvement in the fit indices for the bifactorial model. The Omega hierarchical test clearly differentiated two subfactors of PHQ-9 and GAD-7 items over and above the underlying general factor; however, most of the variance (85.0%) was explained by the general factor and the explained variance of the subfactors was small. The PHQ-9 and GAD-7 performed similarly in detecting post-traumatic stress disorder (PTSD). As defined by conventional cut-offs, depression and anxiety have different prevalence rates in the sample. The scales also differed in their relationships with the short form of health survey (SF-36v2) subscales. The longitudinal analysis showed high stability of depression and anxiety symptoms: 49–67% of the post-TBI patients with comorbid depression and anxiety reported the persistence of the symptoms over time. Discussion: The factorial structure analysis favors a general latent construct underlying both depression and anxiety scales among patients after TBI. We discuss the implications our findings and future research directions. View Full-Text
Keywords: depression; anxiety; bifactorial model; validity; comorbidity depression; anxiety; bifactorial model; validity; comorbidity
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Teymoori, A.; Gorbunova, A.; Haghish, F.E.; Real, R.; Zeldovich, M.; Wu, Y.-J.; Polinder, S.; Asendorf, T.; Menon, D.; CENTER-TBI Investigators and Participants; v. Steinbüchel, N. Factorial Structure and Validity of Depression (PHQ-9) and Anxiety (GAD-7) Scales after Traumatic Brain Injury. J. Clin. Med. 2020, 9, 873.

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