Racial and ethnic differences in the relationship between depression severity and functional status

Objective: Major depression has a negative impact on functional status and quality of life, but little is known about racial or ethnic differences in the relationship between depression and functional disability. This study compared the association between depression severity and functional status among three different racial or ethnic groups. Methods: Data were from participants in the original Patient Health Questionnaire (PHQ) Primary Care Study and PHQ Obstetrics-Gynecology Study (N=5,427). Among the study participants, 62.0 percent were non-Hispanic white, 14.8 percent were African American, and 23.1 percent were Latino. Depression severity was assessed with the PHQ-9, the self-administered DSM-IV criteria-based depression module of the PHQ diagnostic instrument for mental disorders. Functional status was measured with the scales of the Medical Outcomes Study 20-item Short Form Health Survey (SF-20), self-reported disability days, clinic visits, and symptom-related difficulty. Groups were compared in terms of mean PHQ-9 scores and functional status at varying levels of depression severity. Linear regression was used to control for age, gender, education level, and language. Results: Mean PHQ-9 scores were not significantly different between the three different racial or ethnic groups. Similar linear associations were found in all three racial or ethnic groups between increasing PHQ-9 scores (more severe depression) and worsening function on the SF-20 scales and an increased number of disability days and clinic visits. Latinos reported significantly less functional impairment on all measures of functionality compared with non-Hispanic whites. Conclusions: Functional impairment increased with increasing levels of depression severity in all three racial or ethnic groups, although Latinos consistently reported fewer functional disturbances compared with non-Hispanic whites.