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Validation and Standardization of the Generalized Anxiety Disorder Screener (GAD-7) in the General Population

Löwe, Bernd MD, PhD*; Decker, Oliver PhD; Müller, Stefanie MS; Brähler, Elmar PhD; Schellberg, Dieter PhD; Herzog, Wolfgang MD; Herzberg, Philipp Yorck PhD

doi: 10.1097/MLR.0b013e318160d093
Original Article
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Background: The 7-item Generalized Anxiety Disorder Scale (GAD-7) is a practical self-report anxiety questionnaire that proved valid in primary care. However, the GAD-7 was not yet validated in the general population and thus far, normative data are not available.

Objectives: To investigate reliability, construct validity, and factorial validity of the GAD-7 in the general population and to generate normative data.

Research Design: Nationally representative face-to-face household survey conducted in Germany between May 5 and June 8, 2006.

Subjects: Five thousand thirty subjects (53.6% female) with a mean age (SD) of 48.4 (18.0) years.

Measures: The survey questionnaire included the GAD-7, the 2-item depression module from the Patient Health Questionnaire (PHQ-2), the Rosenberg Self-Esteem Scale, and demographic characteristics.

Results: Confirmatory factor analyses substantiated the 1-dimensional structure of the GAD-7 and its factorial invariance for gender and age. Internal consistency was identical across all subgroups (α = 0.89). Intercorrelations with the PHQ-2 and the Rosenberg Self-Esteem Scale were r = 0.64 (P < 0.001) and r = −0.43 (P < 0.001), respectively. As expected, women had significantly higher mean (SD) GAD-7 anxiety scores compared with men [3.2 (3.5) vs. 2.7 (3.2); P < 0.001]. Normative data for the GAD-7 were generated for both genders and different age levels. Approximately 5% of subjects had GAD-7 scores of 10 or greater, and 1% had GAD-7 scores of 15 or greater.

Conclusions: Evidence supports reliability and validity of the GAD-7 as a measure of anxiety in the general population. The normative data provided in this study can be used to compare a subject's GAD-7 score with those determined from a general population reference group.

From the *Department of Psychosomatic Medicine and Psychotherapy, University Medical Center Hamburg-Eppendorf and Hamburg-Eilbek (Schön Clinics), Hamburg, Germany; †Department of Medical Psychology and Medical Sociology, University of Leipzig, Philipp-Rosenthal-Straβe, Leipzig, Germany; and ‡Department of Psychosomatic and General Internal Medicine, University of Heidelberg, Medical Center, Heidelberg, Germany.

Supported by the Friedrich-Ebert-Stiftung, Germany.

Reprints: Bernd Löwe, MD, PhD, Department of Psychosomatic Medicine and Psychotherapy, University Medical Center Hamburg-Eppendorf, Martinistraβe 52, 20246 Hamburg, Germany. E-mail: b.loewe@uke.uni-hamburg.de.

© 2008 by Lippincott Williams & Wilkins.