Background: The Patient Health Questionnaire-9 (PHQ-9) and the Generalized Anxiety Disorder Questionnaire- 7 (GAD-7) are short screening instruments used for detection of depression and anxiety symptoms in various settings, including general and mental health care as well as the general population. The aim of this study is to evaluate psychometric properties and factorial structure of the PHQ-9 and the GAD-7 in a sample of Lithuanian university students.
Methods: 1368 students (mean age 22.5±4.8) completed the PHQ-9 and the GAD-7 questionnaires online; after the completion of the survey, students were asked to provide phone contact for an additional interview. Eligible students were approached later by trained interviewers and completed The Clinical Interview Schedule-Revised for assessment of depressive and anxiety disorders.
Results: Results showed that the PHQ-9 and the GAD-7 are reliable screening tools for depression and anxiety (Cronbach alpha 0.86 and 0.91, respectively). The one-factor structure of the PHQ-9 and the GAD-7 was confirmed by the Confirmatory Factor Analysis. A cut-off of ≥10 for the PHQ-9 resulted in 71% sensitivity and 66% specificity recognizing students with increased risk for mood or anxiety disorder. For the GAD-7, a cut-off ≥9 resulted in 73% sensitivity and 70% specificity recognizing students at risk. The PHQ-9 was sensitive but not specific in recognizing students with depressive disorders. The sensitivity and specificity of the GAD-7 in differentiating students with generalized anxiety disorders were low.
Conclusions: The PHQ-9 and the GAD-7 have sufficient formal psychometric properties, but their clinical utility as diagnostic tools for recognition of depressive and anxiety disorders in students is limited. Due to low specificity and high false positive rates, both scales are recommended only as an initial screening tool for recognition of subjects with increased risk of mental disorders, however positive cases should be later assessed using more comprehensive instruments.