Longitudinal measurement invariance of the Patient Health Questionnaire-9 across racial/ethnic groups: Results from the traumatic brain injury model system study.

Abstract

Purpose/objective: The aim of this article is to evaluate the measurement invariance (MI) of the Patient Health Questionnaire-9 (PHQ-9) in a sample of individuals during the first 2 years after traumatic brain injury (TBI). MI was examined among racial/ethnic groups and over time to determine the utility of the PHQ-9 across these dimensions.

Research method/design: In total, N = 3,227 (20% of the total sample) at 1 year and N = 3,153 (19% of the total sample) at 2 years were included for cross-sectional analyses. For the longitudinal analyses, participants with the PHQ-9 at both time points (N = 2,234; 14% of the total study sample) were included.

Results: Results were that the PHQ-9 is fully invariant and maintains its unidimensional factorial structure across racial/ethnic groups during the first 2 years after TBI, suggesting the scale measures the same construct equally well for participants from each group.

Conclusion/implications: Based on these results, clinicians should feel confident using the PHQ-9 with diverse TBI patient populations, and researchers can reliably and validly employ it in TBI studies across racial/ethnic groups in the United States. Given the high rates of depression among individuals after TBI and its negative impact on their lives, this instrument will continue to be a key tool to measure the prognosis and success of rehabilitation programs. (PsycInfo Database Record (c) 2025 APA, all rights reserved).