Validation of four measures of mental health against depression and generalized anxiety in a community based sample

There is a need to validate screening measures of affective and generalized anxiety disorders for use in epidemiological surveys of mental health in the general population. This study examined the diagnostic accuracy of the Patient Health Questionnaire (PHQ-9), Goldberg Anxiety and Depression Scales (GAS, GDS) and the 12-item Short Form Health Survey (SF-12) Mental Health Component Summary Scale (MCS-12) in a population based longitudinal study in Australia. We report analyses of two narrow age birth cohorts in the Personality and Total Health (PATH) through life study (ages 32-36 and 52-58). Depressive episodes (severe, moderate, and mild), dysthymia and generalized anxiety disorder were diagnosed according to International Classification of Diseases (ICD-10) criteria using the World Health Organisation (WHO) Composite International Diagnostic Interview (CIDI) as a criterion. All scales had high concordance with their target 30-day diagnoses, with area under the Receiver Operating Characteristic (ROC) curve (AUC) ranging between 0.85 and 0.90. The PHQ-9, GDS, GAS and MCS-12 were all valid instruments for identifying possible cases of depression and anxiety, and assessing the severity of these common mental disorders in the general population. We report recommended cut-points for each scale, though note that the optimal cut-point on mental health screening instruments may vary depending on the context of test administration.