Differential item functioning between ethnic groups in the epidemiological assessment of depression

A potential explanation for the finding that disadvantaged minority status is associated with a lower lifetime risk for depression is that individuals from minority ethnic groups may be less likely to endorse survey questions about depression even when they have the same level of depression. We examine this possibility using a nonparametric item response theory approach to assess differential item functioning (DIF) in a national survey of psychiatric disorders, the National Comorbidity Survey. Of 20 questions used to assess depression symptoms, we found evidence of DIF in 3 questions when comparing non-Hispanic blacks with non-Hispanic whites and in 3 questions when comparing Hispanics with non-Hispanic whites. However, removal of the questions with DIF did not alter the relative prevalence of depression between ethnic groups. Ethnic differences do exist in response to questions concerning depression, but these differences do not account for the finding of relatively low prevalence of depression among minority groups.