Validity of the patient health questionnaire-9 in assessing depression following traumatic brain injury

Objective: To test the validity and reliability of the Patient Health Questionnaire-9 (PHQ-9) for diagnosing major depressive disorder (MDD) among persons with traumatic brain injury (TBI). Design: Prospective cohort study. Setting: Level I trauma center. Participants: 135 adults within I year of complicated mild, moderate, or severe TBI. Main Outcome Measures: PHQ-9 Depression Scale, Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (SCID). Results: Using a screening criterion of at least 5 PHQ-9 symptoms present at least several days over the last 2 weeks (with one being depressed mood or anhedonia) maximizes sensitivity (0.93) and specificity (0.89) while providing a positive predictive value of 0.63 and a negative predictive value of 0.99 when compared to SCID diagnosis of MDD. Pearson's correlation between the PHQ-9 scores and other depression measures was 0.90 with the Hopkins Symptom Checklist depression subscale and 0.78 with the Hamilton Rating Scale for Depression. Test-retest reliability of the PHQ-9 was r = 0.76 and K = 0.46 when using the optimal screening method. Conclusions: The PHQ-9 is a valid and reliable screening tool for detecting MDD in persons with TBI.