Scientists have found that racial discrimination literally does hurt, showing that African Americans feel more pain and have greater activity in brain areas linked to stress and trauma than other ethnic groups.
The finding has a tragic and conflicted backstory, with stereotypic views abounding that black people have greater pain tolerance than whites, while scientific evidence routinely shows the reverse to be true.
Despite the science, studies have found that black patients, including children, typically get less pain relief in hospital than non-black patients.
The researchers, led by neuroscientist Tor Wager from Dartmouth College in the US, wanted to find out what might be upping the pain levels felt by African Americans.
There are, they explain in a paper published in Nature Human Behaviour, two main suspects.
First, innate biology could play a role, with some evidence African Americans have genetic changes that tweak the workings of the body’s inner pain killers, the endogenous opioids.
To untangle these effects the team used MRI brain imaging to examine pain responses in 88 adult Americans of African, Hispanic and non-Hispanic White background.
The pain source was a coin-sized heat disc applied to the inside of the forearm at steadily increasing temperature, from 45 to 47 and finally 49 degrees Celsius.
The researchers also took a detailed history, including whether the person had been discriminated against, such as being unfairly denied a bank loan, or treated with less courtesy than other people.
The first finding gave a persuasive answer on the question of biology – African Americans in this study had classic pain pathways nearly identical to the other ethnicities.
A set of brain regions known to become active with pain, called the “neurologic pain signature”, lit up equally on the MRI scans between the differing ethnic groups as the heat was turned up.
But the same could not be said for two other key brain parts.
The ventromedial prefrontal cortex and nucleus accumbens have a big say in our emotions and how we evaluate pain. The strength of connections between the two predicts whether pain becomes chronic, a transition linked to previous trauma. The regions also undergo neuroplastic change with stress.
Both areas showed heightened activity in the African American cohort who, consistent with previous studies, experienced greater overall pain than the other groups.
The researchers were able to show, through a statistical method called regression, that the differences were linked to two troubling traits – a history of discrimination and a lack of trust in the experimenter.
“[I]ncreased exposure to stressful life experiences such as discrimination, and accompanying changes in brain systems related to pain valuation, modulation and chronification, may contribute to heightened pain report in African Americans compared to non-Hispanic White Americans,” they write.
The authors offer a prescription for how medicine, and the community at large, might deal with the issue of ethnic pain differences:
“[I]nterventions aimed at decreasing racial discrimination and increasing clinician trust amongst African Americans may help to alleviate these pain disparities.”
Paul Biegler is a philosopher, physician and Adjunct Research Fellow in Bioethics at Monash University. He received the 2012 Australasian Association of Philosophy Media Prize and his book The Ethical Treatment of Depression (MIT Press 2011) won the Australian Museum Eureka Prize for Research in Ethics.
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