A Comparison of PHQ-9 and TBI-QOL Depression Measures Among Individuals With Traumatic Brain Injury

Purpose/Objective: To compare and contrast how individuals with traumatic brain injury (TBI) are classified (positive or negative screen) by different cut-offs on two self-report measures of depressive symptoms: the PHQ-9, which assesses somatic symptoms, and the TBI-QOL Depression item bank, which does not. Research Method/Design: Three hundred eighty-five individuals with TBI were recruited from six rehabilitation hospitals in the U.S. as part of the calibration data collection for the TBI-QOL patient-reported outcome measurement system. Results: The TBI-QOL and PHQ-9 total scorcs correlated strongly (disattenuated r = .83). The correlation was even stronger (disattenuated r = .92) when the four PHQ-9 somatic items were removed from the total score. When the PHQ-9 was scored traditionally, the rate of agreement was approximately 80-85% using standard cut-offs for each scale. Depending on the cut-off score, 23-26% of participants screened positive on the PHQ-9, whereas 9-38% screened positive on the TBI-QOL Depression. Individuals who screened positive on the PHQ-9 alone reported more somatic symptoms than those who screened positive on the TBI-QOL alone. Individuals who screened positive on the TBI-QOL alone were at slightly greater risk for other negative psychological functioning than individuals who screened positive on the PHQ-9 alone. Conclusions/ implications: The PHQ-9 and TBI-QOL Depression performed similarly in screening for depressive symptoms among individuals with TBI. The PHQ-9 identified more individuals with somatic symptoms, which may overlap with other medical issues, whereas the TBI-QOL Depression instrument identified more individuals who reported other forms of emotional distress.