Diagnosis of depression and use of antidepressant pharmacotherapy among adults in the United States: does a disparity persist by ethnicity/race?

Background And Objective: Both the rate of diagnosis of depression in the US and the rate of prescribing an antidepressant for its treatment have increased substantially over the past two decades. Previous research has also indicated that the rates of diagnosis and treatment of depression with an antidepressant vary widely by ethnicity/race. The objective of this study was to discern ethnic/race-specific (non-Hispanic Black; Hispanic; non-Hispanic White) population-adjusted rates of US office-based physician-patient encounters (office-based visits) documenting a diagnosis of depression, and the extent of the use of antidepressant pharmacotherapy for its treatment.

Methods: Data from the US National Ambulatory Medical Care Survey (NAMCS) for the years 1992-1997 and 2003-2008 were utilized for this analysis. The years 1998-2002 were excluded due to the magnitude of missing data for the variable ethnicity. The US NAMCS is a national probability sample designed and conducted by the US National Center for Health Statistics of the US Centers for Disease Control and Prevention. Depression was defined via International Classification of Diseases, 9th Revision, Clinical Modification codes 296.2-296.36; 300.4; 311. Antidepressants were defined as US National Drug Code category 0630 prior to 2005, and category 249 in Lexicon Plus® thereafter. Data were partitioned into six 2-year time intervals for trend analysis of population-adjusted rates (per 100) among patients aged 20-79 years. Rates per 2-year time interval are based on US Census Bureau national resident population estimates for the ethnicity/race categories examined. Comparisons within and across time-frames were assessed by chi-squared (χ2) analysis. The a priori level of significance for all statistical tests was set at p < 0.05. Analyses were performed using SAS Release 9.1.3.

Results: Over the 12-year time-frame examined, the rate of office-based visits documenting a diagnosis of depression increased 28.4% for non-Hispanic Whites (from 10.9 to 14.0 per 100; p < 0.001), 54.8% for non-Hispanic Blacks (from 4.2 to 6.5 per 100; p < 0.001), and 37.5% for Hispanics (from 4.8 to 6.6 per 100; p < 0.001). The rate of office-based visits with a recorded diagnosis of depression in concert with the prescribing of an antidepressant increased 66.2% for non-Hispanic Whites (from 6.5 to 10.8 per 100; p < 0.001), 69.2% for non-Hispanic Blacks (from 2.6 to 4.4 per 100; p < 0.001), and 36.7% for Hispanics (from 3.0 to 4.1 per 100; p < 0.001).

Conclusion: By 2003-2004, the population-adjusted rates for non-Hispanic Blacks and Hispanics were similar, and remained so through 2007-2008. However, over the 12-year time-frame examined, the rates for both minority groups were, in each 2-year interval, far less than that observed in non-Hispanic Whites. Disparities remain by ethnicity/race in the diagnosis and treatment of depression in the US.