Neural and social factors contributing to ethnic differences in pain

African Americans report feeling higher levels of pain than Hispanic Americans and non-Hispanic White Americans, which may result from changes in pain-related brain circuitry brought about by a history of discrimination. These findings are reported in Nature Human Behaviour. The study identifies a network of brain regions associated with pain valuation, discrimination, and interpersonal context, which contributed to the higher level of pain reported by African Americans as opposed to the other groups.

A common belief since the time of slavery in the United States is that African Americans feel less pain than White Americans. This belief has been linked to under-treatment of pain for African Americans, which contributes to widespread and persistent racial and ethnic health disparities. In fact, African Americans, and in some cases Hispanic Americans, report more pain than non-Hispanic Whites in both clinical and laboratory settings. However, the neurobiological mechanisms underlying these differences are unknown.

Elizabeth Losin and colleagues used fMRI scans during experimental application of painful heat, along with analysis of 19 sociocultural factors to understand ethnic group differences in pain sensitivity. The authors studied 88 participants: 28 African Americans, 30 Hispanic Americans, and 30 non-Hispanic White Americans. They found that the Neurologic Pain Signature, a brain measure that tracks the intensity of physical pain, was largely similar across all three groups. However, African American participants reported more intense pain than others in the cohort, which was mediated by discrimination. The authors also found increased responses to physically painful stimuli in a frontostriatal brain circuit in African American participants, but not the other groups. Activity in this circuit was related to discrimination and experimenter trust. Previous studies have related activity in this circuit to non-physical aspects of pain.

The findings suggest that the higher levels of pain felt by African Americans may arise, in part, from differences in non-physical pain brain systems, which may in turn result from the long-term effects of negative social treatment. The authors recommend interventions geared towards reducing discrimination and increasing clinician trust may be promising ways to mitigate ethnic disparities in pain.

doi: 10.1038/s41562-020-0819-8

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