Examination of the Structure and Function of the Patient Health Questionnaire (PHQ-9) Among Latina and White Female College Students

Background and Purpose: The Patient Health Questionnaire-9 (PHQ-9) is a 9-item measure of depression originally developed as a screening tool in primary care facilities and has subsequently been used in a variety of other settings. Numerous psychometric investigations have supported the use of the PHQ-9 as a unidimensional measure of depression. However, a growing body of research suggests that, like other depression scales, the PHQ-9 is a multidimensional construct that includes both affective and somatic symptomatology. Proper diagnosis and treatment of depression requires reliable and valid measures of assessment, particularly for at-risk populations. The current study examines the dimensionality of the PHQ-9 among female college students. Based on epidemiologic data showing high rates of depression among Latinas, a focused comparison of the dimensionality of this measure among White and Latina students was conducted.

Methods: Data from the Healthy Minds Study, a 4-year web-based survey study of college student mental health, was used in this analysis. Only Latina and White female college students with complete data were included (N = 16,754). The data was randomly divided into two separate samples. Exploratory factor analysis (EFA) was used with one of the samples to examine the factor structure of the PHQ-9 among female college students. Confirmatory factor analysis (CFA) was used with the other sample to allow for a more rigorous test of the factor structure identified in the EFA. A multiple group confirmatory factor (MGCFA) analysis among Latina and White female students was also conducted to examine the stability of the identified model across racial/ethnic groups. Results: The EFA provided evidence for a two-factor structure of the PHQ-9, representing affective and somatic dimensions of depression. The two-factor structure of the PHQ-9 was further supported by the CFA (RMSEA = 0.064, TLI = 0.984, and CFI = 0.990). The MGCFA further revealed that the structure and function of the measure did not differ between White female and Latina college students.

Conclusions & Implications: This study provides evidence for a multidimensional formulation of the PHQ-9 among female college students, where depression is conceptualized as having separate but interrelated affective and somatic symptoms. This distinction may be particularly important among college students where somatic complaints (e.g., being tired, irregular sleeping patterns) may be more common and be less indicative of depression than affective symptoms (e.g., feeling depressed/hopeless). This distinction also helps recognize the heterogeneity in the presentation of depression, which can improve screening, diagnosis, and treatment. Finally, this study also minimizes concern of a construct bias when using this measure within diverse populations, particularly Latina and White college students.