Brain volume disparities among young children of different races may be attributable to adverse childhood experiences related to socioeconomic conditions and structural racism, new research suggests.
Investigators from the Belmont, Mass.–based McLean Hospital, an affiliate of Mass General Brigham, found that 9- and 10-year-old children of different racial and socioeconomic backgrounds have subtle neurobiological differences in gray matter volume in certain brain regions associated with trauma and stress.
Lead investigator Nathaniel Harnett, PhD, of the department of psychiatry at Harvard Medical School, Boston, believes this research shows evidence that “structural racism” – broad socioeconomic disadvantages that lead to poverty and emotional trauma – may affect brain structures and growth and ultimately may lead to psychiatric illness.
“For clinicians, I think the take-home message is that we really need to be more aware about the ways in which the disproportionate burden of stress might impact some groups,” Dr. Harnett told this news organization.
“This in turn can affect the way they respond either to later stress or maybe even treatment outcomes.” He added that other brain regions and compensatory mechanisms are likely to be involved, and more work needs to explore these connections.
The study was published online in the American Journal of Psychiatry.
‘Toxic stressor’
Dr. Harnett and colleagues used MRI and survey data from the 2019 Adolescent Brain Cognitive Development (ABCD) study involving over 12,000 children from 21 sites across the United States.
Participating children provided information about emotional and physical conflicts in the household. The ABCD study also surveyed the parents about their race and ethnicity, parental education, employment, and family income. Another factor in the analysis was neighborhood disadvantage, based on the Area Deprivation Index utilizing 17 socioeconomic indicators from the U.S. Census, including poverty and housing.
Comparing brain MRI findings from approximately 7,300 White children and 1,800 Black children in the ABCD study, Dr. Harnett’s group found that Black children had lower gray matter volume in the amygdala, hippocampus, and other subregions of the prefrontal cortex.
Experience of adversity was the “sole factor” explaining brain volume differences, with household income being the predominant factor.
Compared with White children, Black children were three times less likely to have parents who were currently employed. In addition, White parents were more likely than Black parents to have higher education at 75.2% versus 40.6%. Black families had significantly lower household income than White families and experienced more family conflict, material hardship, neighborhood disadvantage, and traumatic events.
The researchers analyzed race-related differences in posttraumatic stress disorder symptoms and the relationship with adversity and found that Black children had significantly greater PTSD symptom severity, and that symptom severity was “further predicted by adversity.”
“Taken together, early-life adversity may act as a toxic stressor that disproportionately impacts Black children as a result of their significantly greater exposure to adversity and contributes to differential neural development of key threat-processing regions,” the investigators write.
“These parts of the brain are involved in what we typically call threat learning,” Dr. Harnett explained. “Threat learning is basically learning to recognize potential dangers in our environment and selecting behaviors to keep us safe, whether we’re going to run away from a danger or face it head on. When you have chronic exposure to things that can be dangerous or can make you feel unsafe, that might have an impact on how these brain regions develop, with potential implications for how these regions function later on in life.”