Validity of the patient health questionnaire (PHQ-9) as a screening tool for depression amongst Nigerian university students.

BACKGROUND: The common self-rated depression scales are lengthy, old and do not reflect the current diagnostic classifications criteria of depressive disorders. This study aimed to validate the Patient Health Questionnaire (PHQ-9) as a screening tool for depression amongst Nigerian university students.

METHODS: A representative sample of university students (n=512) completed the PHQ-9 and the Beck's Depressive Inventory (BDI). They were also interviewed for clinical diagnoses of depressive disorders using the Mini International Neuropsychiatric Interview (MINI).

RESULTS: The internal consistency of questions within the PHQ-9 was 0.85. The PHQ-9 had good concurrent validity with the BDI (r=0.67, P<0.001). It also had a good (r=0.894, P<0.001) one month test-retest reliability. Using the Receiver Operating Characteristic (ROC) curve, the optimal cut-off score for minor depressive disorder is 5 (sensitivity 0.897, specificity 0.989, Positive Predictive Value - PPV 0.875, Negative Predictive Value - NPV 0.981 and Overall Correct Classification - OCC rate 0.973) while for major depressive disorder only is 10 (sensitivity 0.846, specificity 0.994, PPV 0.750, NPV 0.996 and OCC rate 0.992).

LIMITATIONS: The study limitations include use of a specific group in community, moderate sample size and screening for only minor and major depressive disorders while neglecting other depressive disorders.

CONCLUSIONS: The PHQ-9 has good psychometric properties amongst Nigerian university students. Because of its validity, reliability, brevity and ease of administration, the PHQ-9 will be a valuable tool for estimating depression amongst college students in Nigerian community. More studies are needed to test the usefulness of the translated local language versions of this instrument amongst the community in sub-Saharan Africa.