Psychometric Validation of the Patient Health Questionnaire-4 (PHQ-4) Among Returned Cambodian Migrant Workers

Background Ultra-brief mental health screening tools are increasingly needed for use in large-scale surveys and resource-constrained settings, particularly among migrant populations in low- and middle-income countries (LMICs). The Patient Health Questionnaire-4 (PHQ-4) is a widely used instrument for assessing anxiety and depression; however, its psychometric properties have not been validated among returned migrant workers in Cambodia. Methods A cross-sectional study was conducted among 392 returned Cambodian migrant workers recruited from four provinces in 2022. Internal consistency was assessed using Cronbach’s alpha. Confirmatory factor analysis (CFA) was performed to compare one-factor and two-factor models. Construct validity was evaluated by examining associations between PHQ-4 scores and occupational health risk factors using multivariate logistic regression. Results The PHQ-4 demonstrated acceptable internal consistency (α = 0.78). CFA supported a two-factor structure representing anxiety and depression, which showed superior model fit compared to the one-factor model (CFI = 0.97, TLI = 0.95, RMSEA = 0.05, SRMR = 0.03). The two factors were moderately correlated (r = 0.63). Higher PHQ-4 scores were significantly associated with long working hours (AOR = 1.45, 95% CI: 1.10–1.92), unsafe working conditions (AOR = 1.63, 95% CI: 1.21–2.20), and hazardous work exposure (AOR = 1.38, 95% CI: 1.05–1.82), supporting construct validity. Conclusions The PHQ-4 is a reliable and valid ultra-brief screening tool for assessing anxiety and depression among returned Cambodian migrant workers. Its brevity and strong psychometric performance support its use in large-scale surveys, occupational health assessments, and community-based mental health screening in migration-affected populations in LMICs.