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

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 (alpha = 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.