In a study of over 9,000 children that examined structural magnetic resonance imaging (MRI) data as well as parent and child self-reporting of adversity-related measures, researchers found that greater exposure to adversities for Black children was linked to lower gray matter volume in the amygdala and multiple subregions of the prefrontal cortex in comparison to White children.
Emerging research suggests that disparities with adversity exposure in childhood may have an impact on race-related differences in neural circuitry structure that can be associated with neurological disorders such as post-traumatic stress disorder (PTSD).
For the study, recently published in the American Journal of Psychiatry, researchers examined data from 9,382 children (nine to 10 years of age) who were participants in the Adolescent Brain and Cognitive Development (ABCD) Study. The study population was comprised of 7,516 White children and 1,866 Black children. The researchers noted that 52 percent of the cohort were male (4,921) and 48 percent were female (4,461).
Examining environmental and brain structure relationships, the study authors reviewed structural magnetic resonance imaging (MRI) data as well as a number of socioeconomic factors (including parental education, employment status and family income) and adversity measures (such as neighborhood disadvantage, family conflict, material hardship and trauma history).
The researchers found differences in gray matter volume in 11 of 14 a priori brain regions of interest with White children demonstrating greater greater gray matter volume in the amygdala, hippocampus, lateral orbitofrontal cortex, caudal anterior cingulate and other regions. In comparison to White children, the researchers found that Black children lived in more disadvantaged neighborhoods and had greater exposure to material hardship, traumatic events, and family conflict. The study authors also noted that 75.2 percent of White parents graduated from college in comparison to 40.6 percent of Black parents. Eighty-eight percent of White parents made $35,000 or more a year in comparison to 46.7 percent of Black parents, according to the study.
With the exception of trauma history and family conflict, the study authors noted unique effects on all adversity indices with income disparity having an impact on gray matter volume in eight of the 14 a priori brain regions of interest.
“Greater exposure to these adversities was linked to lower gray matter volumes in the amygdala and several subregions of the (prefrontal cortex). Accordingly, Black children showed lower gray matter volumes in the amygdala, the hippocampus, and several subregions of the (prefrontal cortex) compared with White children,” wrote lead study author Nathalie M. Dumornay, B.S., who is affiliated with the Division of Depression and Anxiety Disorders at McLean Hospital in Belmont, Mass., and colleagues.
(Editor’s note: For related content, see “What a New MRI Study Reveals About Brain Aging and Racial Disparities.”)
In supplementary analyses, the researchers also noted a significant correlation between higher adversity exposure and symptoms of PTSD.
“Black children had significantly greater PTSD symptom severity, and symptom severity was further predicted by adversity. Accounting for adversity partially mediated race-related differences in PTSD symptoms but also attenuated correlations between regional gray matter volume and PTSD symptom severity,” noted Dumornay and colleagues.
Pointing to the rapid development of the prefrontal cortex, amygdala, and hippocampus from early childhood to early adulthood, the study authors noted that toxic stress, or prolonged exposure to adverse experiences, during this period can disrupt the evolving architecture of the brain.
“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,” noted Dumornay and colleagues.
In regard to study limitations, the researchers noted that the study did not include children of other racial identities beyond parent-identified Black and White children. Dumornay and colleagues acknowledged there was a lack of longitudinal MRI data and information as to the timing and duration of adversity exposure in the study cohort. The study authors maintained that increased representation of non-White racial and ethnic groups and greater clarity as to when and how long children experienced adversities could be points of emphasis in future research.