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Gray matter volume in key brain regions was lower in Black children compared with white children, likely due to disparities in childhood adversity, according to data from the Adolescent Brain Cognitive Development () study.

Among children ages 9 to 10 years, white kids showed greater gray matter volumes compared with Black kids in the amygdala, hippocampus, frontal pole, superior frontal gyrus, rostral anterior cingulate, pars opercularis, pars orbitalis, lateral orbitofrontal cortex, caudal middle frontal gyrus, and caudal anterior cingulate (all P<0.001), reported Nathaniel Harnett, PhD, director of the Neurobiology of Affective Traumatic Experiences Laboratory at McLean Hospital in Belmont, Massachusetts, and co-authors.

Compared with white children, Black children had experienced more traumatic events, material hardship, and family conflict and lived in more disadvantaged neighborhoods, while their parents/caregivers had lower income and educational attainment and were more likely to be unemployed, they noted in the .

"Greater exposure to these adversities was linked to lower gray matter volumes in the amygdala and several subregions of the PFC [prefrontal cortex]," Harnett and team wrote. "Taken together, our findings highlight the impact that disparities in early-life adversity have on race-related differences in the structure of neural circuitry associated with PTSD and other trauma- and stress-related disorders."

Of note, income was the most common predictor of gray matter volume disparities, they said.

This analysis provides additional evidence that contradicts claims about inherent race-related differences found in the brain, Harnett told 乌鸦传媒.

"The disproportionate burden of structural inequities that we place on some groups has measurable impacts on their brain, and these impacts begin even in kids as young as 9 and 10 years old," he said. "Our work occupies a little bit of a unique spot in both trying to figure out how does adversity impact the brain in general, and then also how are minoritized and racialized individuals -- who more often experience these adversities -- uniquely impacted by these experiences?"

In the discussion of their study, Harnett and colleagues noted that "early-life adversity can have lasting negative consequences on mental health in adulthood," noting that prior studies have found positive associations between childhood adversity and prevalence of poor psychosocial and behavioral outcomes later in life, including PTSD, anxiety, depression, drug and alcohol use, low life satisfaction, suicide attempts and ideation, and perpetration of violence.

"It's important for people in the clinical sphere to really consider how the experiences that people have might shape their behavior and differentially between racial and ethnic groups," Harnett said. "If you're seeing patients that have this sort of wide range of adverse experiences in their lives, how is that going to impact the treatment that you're giving them?"

In an , Deanna M. Barch, PhD, and Joan L. Luby, MD, of Washington University in St. Louis, noted that this study is an important step in understanding the role that social factors play in a person's health, as well as the role of racial disparities in mental health outcomes.

"The aims of the analysis were clearly intended to begin to elucidate and correct the long history of reporting of differences in health, behavioral, and neural outcomes attributed to race and/or ethnicity," they wrote. "These old models generally failed to appreciate and account for the powerful effects of the psychosocial environment on biological processes, including brain development, drawing oversimplified false conclusions about biological differences attributed to race."

Harnett emphasized that because these brain regions are known to be important for regulation of emotions, the study findings suggest that addressing structural inequities could have an effect on Black children's futures and potential adverse psychiatric outcomes in adulthood.

"These are kids," he said. "They didn't get to choose where they were born. They didn't get to choose the circumstances, their parents, and yet they're still being asked to shoulder the burden of these adversities in ways that are proving to be toxic for their brain and might have an impact on their development later on in life."

"I think that all of us in the clinical sphere, in the research sphere, and the policy sphere, really need to think about what we can do to mitigate the potentially deleterious effects that these aspects of structural racism might have on development," he added.

Matthew L. Edwards, MD, of Stanford University School of Medicine in California, who was not involved in the study, agreed that it is important to consider the effects of these disparities, but he also noted that researchers and clinicians should be careful about interpreting these kinds of data as it relates to racial differences.

"When you look at racial differences in health, you see the circumstances that are assigned to people of a particular racial group," he told 乌鸦传媒. "It's not that the person has black skin or brown skin; it's that the person is exposed to X, Y, and Z factors because they belong to a particular racial group."

"The point that is often lost in biological and medical research is that race is not the stressor or the factor, structural racism is," he added.

For this study, Harnett and colleagues analyzed data on 7,350 white children and 1,786 Black children from the ABCD cohort who were 9 or 10 years old at the time of recruitment from March to July 2019. The overall study group was about equally divided between boys and girls.

Participants were recruited from public and private schools across the U.S. and accessed for a range of social measures, including family arrangements, neighborhood disadvantages, and trauma history using parent and child self-reports and U.S. Census data. All participants underwent a structural MRI.

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