The psychometric properties of the Generalized Anxiety Disorder scale (GAD-7) in a sample of older individuals from the Icelandic population

Background: The Generalized Anxiety Disorder (GAD-7) questionnaire was developed to screen for generalized anxiety disorder (GAD) in primary care settings, however, the measure may also be used to assess anxiety symptoms in general. Various study results have revealed that different language versions of the GAD-7 have good to excellent psychometric properties across clinical settings and in the general population. In this study, we assessed the psychometric properties of an Icelandic version of the GAD-7 and general anxiety symptoms in a large population-based sample of Icelanders above age 40, as part of a comprehensive study of evaluating the value of screening for a precursor of myeloma in this population. Methods: Individuals born prior to the year 1976 (i.e., 40 years or older) were offered participation and 78,582 consented being screened for monoclonal gammopathy of undermined significance (MGUS). About half the individuals (46%; n = 36,139) that provided consent to being screened for MGUS completed the GAD-7, Patient Health Questionnaire (PHQ-9), and Satisfaction with Life Scale (SWLS), and two single item measures for worry and happiness. Internal consistency, item analysis, and construct validity for the GAD-7 were assessed. Results: Average score on the GAD-7 was relatively low, and females tend to report more anxiety than males and the trend was the same across all age groups. Internal consistency was good (Cronbach’s α’s = .88). Item analysis revealed that the more severe response options were more often used by participants who reported more anxiety. Correlations with scores on other scales (i.e., PHQ-9, r (34,784) = .76, p < .001; SWLS, r (34,745) = -.47, p < .001; worry, r (34,745) = .32, p < .001; happiness, r (34,745) = -.42, p < .001) measuring concepts often associated with GAD were good, indicating good construct validity. Conclusions: The Icelandic general population reported low but comparable anxiety to community samples in other countries. Females seem to feel more anxious than males and people, on average, report less anxiety with increasing age, which is different from studies conducted in other countries. Results from the current study show similar psychometric properties as prior studies on the scale, and scores indicate that the Icelandic population age 40 and over feel not much anxiety in daily life