Depressive symptoms among medical students: comparing three measures in nine countries

Prevalence estimates of depression among medical students are heterogeneous. To investigate this, we evaluated the cross-cultural measurement invariance and case-finding concordance of three depression screening tools across nine countries. This enabled standardized prevalence comparisons and the identification of sociodemographic factors associated with depressive symptoms across multiple countries.

A cross-sectional online survey assessed medical students from ten institutions across nine countries. Measurement invariance across countries was assessed for each instrument. We estimated pooled apparent prevalence via random-effects meta-analyses, evaluated diagnostic concordance between instruments, and identified associated sociodemographic factors using logistic regression.

The sample included 2,733 students (mean age 22.3; 60.7% female). The Patient Health Questionnaire-9 (PHQ-9) and Depression, Anxiety and Stress Scale-Depression subscale (DASS-D) achieved strict measurement invariance, whereas the Center for Epidemiologic Studies Depression Scale (CES-D) was structurally unstable. Pooled prevalence varied markedly by tool: 36.1% (95% CI: 26.9-46.4%, I²=96.1%) for PHQ-9, 43.8% (95% CI: 36.6-51.4%, I²=93.0%) for DASS-D, and 56.4% (95%CI: 49.2-63.3%, I²=92.2%) for CES-D. Only 40.1% of positive screens were concurrently identified by all three instruments. Female sex and lower subjective social status were consistently associated with higher odds of depressive symptoms.

Depression prevalence estimates are highly tool-dependent. The PHQ-9 and DASS-D offer robust frameworks for global comparisons, while the CES-D should be used cautiously. The cross-cultural consistency of female sex and lower social status as risk factors highlights the need for targeted institutional mental health strategies.