Toward a Better Understanding of Racial and Ethnic Differences in Cognitive Function in MDD

Major Depressive Disorder (MDD) is a highly pervasive and disabling disease that is characterized by persistent sadness and loss of interest. It creates a host of complications for the individual and affects various domains of functioning and quality of life. Although the prevalence for MDD is estimated to be higher in the white, non-Hispanic population, MDD still has a significant prevalence among other races and ethnicities. Due to the disparities in diagnosis and treatment in MDD, the burden of disability is increased in minority populations. To begin understanding what factors could possibly contribute to disparities in MDD, it is important to examine key players in MDD such as cognitive functioning. One increasingly recognized impact of depression that can be seen across all populations and ages is cognitive dysfunction, which plays a role in depression severity and recurrence. The examination of potential differences in cognitive function associated with race and ethnicity in depressive disorders has been underexplored. Apart from race/ethnicity itself, there are independent factors highly prevalent in minority populations including social determinants of health (SDOH) such as age and education, and medical or metabolic comorbidities, that independently impact cognitive functioning and depression. This broad investigation was broken into two parts. Part One focused on understanding the current knowledge and findings of racial and ethnic differences in cognitive performance in adults with MDD and possible contributors to those differences. This literature review found associations between race/ethnicity and cognitive functioning as well as other possible contributors to cognitive performance such as age, education, and presence of medical comorbidities such as HIV, metabolic syndrome, and obesity. Part Two of the investigation was a secondary analysis that compared group differences (between Black/non-Hispanic, White/non-Hispanic, and White/Hispanic participants) on measures of cognitive functioning using the National Institute of Health (NIH) Toolbox - Cognition Battery (NIHTB-CB). Significant mean group differences were observed across the Fluid and Total NIHTB-CB cognitive composite scores, with Black participants scoring lower than White, non-Hispanic/Latinx participants. Several differences remained significant when controlling for depressive symptomatology, metabolic function, and medical comorbidity burden. These results indicate that Black, non-Hispanic/Latinx race is a possible contributor to differences in cognitive performance in depression that is independent of depression, metabolic factors, and medical comorbidity burden, although the size of the noted differences may not be clinically meaningful. Future studies are needed to better understand contributors to such differences in cognitive performance and further expand our understanding of depression and development of precision medicine.