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Human beings have the innate desire to be accepted, so it should come as no surprise that discrimination can have a significantly detrimental impact towards one’s emotional state. However, not everyone may be aware of just how detrimental discrimination can be. Previous research studies have shown that there is a strong link between discrimination and negative health outcomes, such as cardiovascular disease, anxiety, and depression.

Prior studies have allowed for these links to be well-researched and understood, but up until recently, the underlying biological mechanisms behind the effect that discrimination has on both mental and physical health have yet to be explained. Tien Dong, MD, PhD, faculty member at the UCLA Digestive Diseases Division and his team of researchers at the University of California, Los Angeles (UCLA) set out to explain what is occurring at the biological level. Understanding the biological pathways is one step towards finding better treatments for those who are faced with poor health outcomes as a result of discrimination.

“…the underlying biological mechanisms behind the effect that discrimination has on both mental and physical health have yet to be explained.”

The study was designed in hopes to better understand the dysregulation specifically in the brain-gut microbiome (BGM) system that occurred as a result of discrimination. The BGM refers to the network of bidirectional interactions between the brain, the gut and its microbiome. The study consisted of 154 research participants who lived in Los Angeles and self-reported as either Asian American, Black, Hispanic, or White. The researchers used self-report questionnaires to measure their levels of chronic discrimination. To understand the BGM system, brain fMRI scans and fecal samples were evaluated for alterations in brain networks, and gut microbial composition respectively.

The groups of participants’ experience of the cause of their discrimination varied, yet each group self-reported about the same levels of discrimination despite their race or ethnicity. While Asian American, Hispanic, and Black participants frequently reported their racial background or skin color as the attributed cause of their discrimination, White participants reported their gender or age as the cause. Despite the reported levels of discrimination being the same regardless of race, the way in which the biological mechanisms were affected appeared to vary among participants of each race/ethnicity.

Discrimination was linked to increased activity in both self-reflection and pain-related processing regions of the brain. Experiences of discrimination were found to be associated with higher levels of stress, resulting in heightened cognitive load and anxiety. Researchers found that the brain scans of Black participants had associations with increased connectivity in regions of the brain that are associated with self-recollection of past experiences and also emotional regulation. Hispanic participants had heightened vigilance associated with discrimination. Regardless of race, those who experienced more discrimination were more likely to be faced with early-life trauma, depression, anxiety, and visceral sensitivity than those who did not.

“These experiences of discrimination are associated with higher levels of stress, resulting in heightened cognitive load and anxiety.”

Furthermore, the brain scans of the Asian American participants showed increased connectivity in regions associated with social and physical pain. White participants who experienced discrimination showed enhanced resting-state connectivity in numerous neural networks, including the regions that are responsible for emotional regulation and reward. These findings suggest less ability of White participants to effectively cope with discrimination when compared to the other races/ethnicities in the study.

The various racial groups of the participants had also experienced differences in the gut microbiome and levels of inflammation. Researchers tested for different bacterial species in the gut—one being Prevotella copri, a gut bacteria associated with high levels of inflammation and susceptibility to arthritis. P. copri was the only bacteria that was found to be statistically different across the various racial groups. It was highest in Black and Hispanic participants, and lowest for White participants. P. copri has been shown to thrive in inflammatory environments, as well as increase inflammation.

Dong and his team of researchers looked for an explanation as to why different races would experience biological differences when it comes to the effects of discrimination. They concluded that a possible reason as to these changes could be the experience of discrimination at different life stages. Since discrimination towards skin color can be experienced in early adolescence (whereas discrimination towards age and gender are more likely to occur later in life) then perhaps the developing brain and gut microbiome of a child is more suspectable to discrimination having the power to modify these structures. While there are other plausible explanations, such as cultural differences, more research is needed in the future before fully understanding just how these factors contribute to the biological changes.

The study was able to clearly conclude that discrimination is associated with negative alterations of brain networks which relate to emotion, cognition, and self-perception. These alterations can increase the risk for mental illnesses such as depression and anxiety. Beyond the implications discrimination has on mental health, it was also associated with compositional and functional changes in the gut microbiome. The UCLA research has clearly demonstrated the biological dysregulation of the BGM system, behind the already known association between discrimination and negative health outcomes.

“Beyond the implications discrimination has on mental health, it also caused negative physical health effects such as visceral sensitivity resulting in structural and functional changes in the gut microbiome.”

The fear, anticipation, and experience of discrimination can set off many alarm bells at a physiological level. With the heightened stress from such a negative experience, it is no surprise that the body of an individual faced with discrimination can lead to dysregulation at both a physical and psychological level. Discrimination has the power to alter our biological pathways and lead to poor health outcomes, making it an important public health issue.

While society still has quite a way to go before resolving systemic discrimination, the UCLA team believes that the outcomes of this study will be able to serve as a way to intervene with the negative health outcomes being caused by discrimination. Understanding the biological mechanisms that discrimination can cause, brings greater urgency to prevent discrimination in the first place and to develop more targeted approaches for affected individuals before they get sick.