PHQ9 Differential Item Functioning

Grant Details

Funder: NIMH (MHRN III Feasibility Pilot Program)

Grant Number: U19MH121738

Project Period: 7/1/2020 – 6/30/2021


Background: Depression and suicide screeners like the Patient Health Questionnaire 9 (PHQ-9) are widely employed within healthcare systems in the U.S. as part of measurement-based care. Some research suggests the full or partial cross-cultural equivalence of the PHQ-9 among different racial and ethnic groups, including the standard one-factor model (Harry & Waring, 2019; Keum, Miller, & Kurotsuchi Inkelas, 2018; Merz et al., 2011; Patel et al., 2019), although in some cases two-factor models have presented the best fit (Granillo, 2012; Harry & Waring, 2019; Harry, Coley, Waring, & Simon, under review; Keum et al., 2018). Findings of cross-cultural equivalence allows for meaningful comparisons to be made in scale mean scores between different cultural groups. However, research has also shown the differential item functioning for some PHQ-9 items based on race (Huang et al., 2006). Furthermore, little cross-cultural research is available on the PHQ-9 that includes American Indian/Alaska Native people (AI/AN) (Harry & Waring, 2019; Harry et al., under review). This is even though AI/AN people have a higher rate of suicide than the general population (Curtin & Hedegaard, 2019) and few studies have researched depression prevalence among this group (Garrett et al., 2015). While available evidence suggests elevated depression rates amongst AI/AN people, most research has focused on individual tribal groups, and the little research that has included national samples has primarily only included those who identify solely as AI/AN and not additional racial or ethnic groups (Asdigian et al., 2018). Depression prevalence may differ between sub-populations of AI/AN people (Asdigian et al., 2018). Mental and behavioral health scales may also function differently between separate tribal or cultural AI/AN groups (Walls et al., 2018).

Recent studies have begun to fill the gap on the cross-cultural equivalence of the PHQ-9 with AI/AN people. Current findings have been mixed, including the study by Harry and Waring (2019) with a general patient population and another study by Harry et al. (under review) that included only those with mental health or substance abuse disorder diagnoses, suggesting that more research is needed. It is unknown if any individual PHQ-9 items function differently between AI/AN people and other racial and ethnic groups (Harry et al., under review). Both researchers and clinicians would benefit from understanding how individual PHQ-9 items function for different groups of AI/AN people and in comparison to other diverse racial and ethnic groups. This is a timely opportunity to extend our work by leveraging the findings from our prior research in this area, focus more closely on the functioning of item 9 between racial and ethnic groups, as well as develop additional preliminary results for a future R01 grant application.

This project supports the NIMH strategic goal of striving for prevention and cures. It does so by focusing on the cultural context component of developing strategies for tailoring existing interventions to optimize outcomes.

Research Question: In a patient population with mental health or substance abuse disorder diagnoses, how do individual PHQ-9 items function for AI/AN adults and other diverse racial and ethnic groups?

Methods: The differential item functioning of PHQ-9 items would be assessed using item response theory, or how different groups with differing levels of depression endorse PHQ-9 items. We would compare two geographically and culturally distinct groups of AI/AN adults (ages 18 to 64), as well as groups of Hispanic, non-Hispanic Native Hawaiian/Pacific Islander, non-Hispanic White, non-Hispanic Black, and non-Hispanic Asian adults. This study would be conducted using existing data from prior research and therefore would not require additional analyst support. The project has already been approved by the Essentia Health Institutional Review Board.

Planned Product: The primary product would be a paper presenting our results. Those results would also provide additional preliminary data for a series of broader, multi-MHRN site NIH grant applications on the cross-cultural assessment of depression and suicide risk and culturally competent interventions for AI/AN people and other indigenous groups, like Native Hawaiians. Collaboration with local tribal communities and researchers would be emphasized.

Lead Site: Essential Rural Health Institute (PI Melissa Harry)

Participating Sites: N/A

Current Status

Paper is under review with Psychological Assessment as of 10/12/2022.

Summary of Findings