Thesis (Ph. D.)--Carleton University, 2001. / Includes bibliographical references (p. 439-455). Also available in electronic format on the Internet.

Indiana University-Purdue University Indianapolis (IUPUI) / Importance: Despite its widespread use in clinical settings and in behavioral medicine research, little is known about the psychometric performance of the PHQ-9 across major U.S. sociodemographic groups. Thus, utilizing a large sample representative of the U.S. population and confirmatory factor analysis (CFA), we determine the factor structure and measurement invariance of the PHQ-9 across groups based on sex, race/ethnicity, and education level. Objective: Our objective was to address key knowledge gaps by definitively determining the factor structure and measurement invariance of the PHQ-9 across major U.S. sociodemographic groups based on sex, race/ethnicity, and education level. Design: The continuous National Health and Nutrition Examination Survey (NHANES) is a cross-sectional, epidemiologic study designed to assess the health and nutritional status of the U.S. population. We examined data from the 2005-2014 survey years. Setting: NHANES is uses a stratified multistage probability sampling approach to enroll civilian, non-institutionalized adults and children in the U.S. Participants: For our final sample, we selected the 26,202 adult respondents with no missing PHQ-9 data. The factors of interest were sex (49.3% men, 50.7% women), race/ethnicity (48.9% non-Hispanic White, 23.7% non-Hispanic Black, 17.8% Mexican American, 9.7% other Hispanic), and education level (9.9% less than 9th grade, 16.6% 9th-12th grade but no diploma, vii 23.7% high school graduate/GED or equivalent, 28.9% some college or Associate’s degree, 20/8% college graduate or above). Main Outcome(s) and Measure(s): The Patient Health Quessionnaire-9 (PHQ-9) Results: Results revealed that the best solution for the PHQ-9 consists of a cognitive/affective factor (items 1. anhedonia, 2. depressed mood, 6. feelings of worthlessness, 7. concentration difficulties, 8. psychomotor disturbances, and 9. thoughts of death) and a somatic factor (items 3. sleep disturbance, 4. fatigue, and 5. appetite changes; RMSEA = 0.034, RMSEA 90% CI = 0.032–0.036, TLI = 0.984, CFI = 0.988). To evaluate measurement invariance, we then conducted single-group and multiple-group CFAs to carry out the 5 steps of measurement invariance testing. Dimensional, configural, weak factorial, strong factorial, and strict factorial invariance was established for the PHQ-9 across the sex, race/ethnicity, and education level groups, as all models demonstrated close fit and the ΔCFI was < 0.010 for all steps. Conclusions and Relevance: Using a U.S. representative sample, we determined that a two-factor solution for the PHQ-9 with a cognitive/affective factor and a somatic factor is invariant across sex, race/ethnicity, and education level groups. Therefore, clinically, the PHQ-9 is an acceptable measure to utilize in major U.S. sociodemographic groups, extending the use of this depression screener from the primary care clinic to the community. Additionally, we show that PHQ-9 cognitive/affective and somatic subscale scores have the same meaning and can be compared across major U.S. sociodemographic groups and provide a consistent, evidence-based approach to computing PHQ-9 subscale scores to be used in future studies.