Abstract
This study examined the psychometric properties of the Patient Health Questionnaire-4 (PHQ-4) as an ultra-brief screener of depression and anxiety in the Philippines during the COVID-19 outbreak. Data from 4,524 non-clinical community respondents aged 18-73 years old was collected online between March and July 2020. We evaluated the screener's factor structure, measurement invariance, and criterion-related validity using confirmatory factor analysis (CFA), multigroup CFA, and structural equation modeling (SEM), respectively. We also evaluated the accuracy of the PHQ-4 cut-off scores by comparing the them with the screeners' full scales (i.e., PHQ-9 and GAD-7). Using the cutoff scores of the screeners, we also estimated the prevalence rates of depression and anxiety. The PHQ-4 has good internal reliability (Cronbach's α = 0.82). The CFA results show that the two-factor model has an excellent model fit that is superior to the one-factor model. The two-factor model held through increasingly constrained multigroup CFA models across gender, age, and geographical location groups, demonstrating measurement invariance. The SEM model supported the PHQ-4's theoretical association to stress, negative affect, and positive affect, supporting the screener's criterion-related validity. In estimating prevalence rates, among those screened by the PHQ-4 cut-off scores for depression (n = 1,905, 42.11%) and anxiety (n = 1,853, 40.96%), 81.78% and 94.06% were consequently screened by the PHQ-9 and GAD-7, respectively. This study supports the reliability, validity, and measurement invariance of the PHQ-4 as an ultra-brief screener of depression and anxiety in a large community sample in Southeast Asia. The inclusion of ultra-brief screeners in COVID-19-related studies and other human disasters, especially among non-clinical samples in low- and middle-income countries, is relevant for the sustainable evaluation and monitoring of the severity mental health symptoms leading to timely and effective mental health service provision.