A new meta-analysis of functional magnetic resonance imaging (fMRI) studies reveals that prior adversity exposure is linked to higher reactivity in the amygdala and lower reactivity in the prefrontal cortex (PFC), brain regions associated with assessment of possible threats and subsequent behavioral coping mechanisms.
For the meta-analysis, recently published in JAMA Network Open, the authors searched multiple literature databases for functional MRI studies of patients with trauma, post-traumatic stress disorder (PTSD), adversity, stress, maltreatment, and those affected by abuse or poverty. The researchers ultimately reviewed data from 83 fMRI studies and examined the impact of adversity exposure across neurocognitive domains including emotion processing, memory processing, inhibitory control, and reward processing in a total of 5,242 study participants, according to the study.
In 50 of the reviewed studies (including 3,413 participants) that examined emotion processing tasks, the meta-analysis authors noted higher amygdala reactivity for the adversity exposure group in 45 of the studies and lower PFC reactivity for the adversity exposure group in 25 studies.
“The primary results of this meta-analysis provide clear evidence that a history of severe adversity is associated with long-lasting increases in adult amygdala responses and decreases in PFC responses to diverse psychological challenges,” wrote study co-author Marco Leyton, Ph.D., a professor in the Department of Psychiatry at McGill University in Montreal, Canada, and colleagues.
The meta-analysis authors noted that the amygdala plays a critical role in the assessment of threats and subsequent defensive actions. Multiple studies have demonstrated higher amygdala reactivity and PFC hyporesponsiveness during emotion processing for people with PTSD, according to the researchers.
Three Key Takeaways
- Amygdala reactivity and adversity. The meta-analysis demonstrates that individuals with a history of prior adversity exposure show heightened reactivity in the amygdala. This heightened amygdala response is associated with the assessment of potential threats and defensive actions, which could have clinical implications for understanding emotional processing in individuals with a history of trauma and adversity.
- Prefrontal cortex (PFC) reactivity. The study reveals that individuals exposed to adversity exhibit lower reactivity in the prefrontal cortex (PFC). The PFC is involved in higher-order cognitive functions, including inhibitory control and rational decision-making. Reduced PFC activity suggests potential challenges in coping mechanisms and emotional regulation in those with a history of adversity.
- Trauma vs. moderate adversity. The meta-analysis highlights differences in brain reactivity between individuals who have experienced trauma-related adversities and those who have faced moderate adversities. Trauma-exposed individuals showed significantly greater amygdala activation and lower PFC activation, while no significant differences were observed in individuals with moderate adversity. This differentiation suggests that the nature and severity of adversity may have distinct effects on brain function and emotional processing.
Comparing research findings from 65 studies (total of 4,003 study participants) that examined trauma-type adversities versus the fMRI findings from 18 studies (total of 1,239 participants) that looked at moderate adversities, the meta-analysis authors found that the trauma adversity group had significantly greater bilateral amygdala activation in 56 studies and significantly lower PFC in 36 studies. For the 18 studies examining the impact of moderate adversities, researchers saw no significant differences across the aforementioned neurocognitive domains.
“This analysis recapitulated our general findings, showing increased amygdala activation and reduced PFC activation in trauma-exposed individuals. In contrast, significant activations were not found when analyzing prior moderate adversities,” noted Leyton and colleagues. “This difference between traumas and moderate adversity is compelling, although moderate adversity is a broad conceptualization and different authors have defined it as poverty, minority stress, and sexual orientation identity stress.”
(Editor’s note: For related content, see “New MRI Study Examines Impact of Disparities with Childhood Adversity Exposure on Brain Development,” “What a New MRI Study Reveals About Brain Aging and Racial Disparities” and “FDA Clears AI-Powered Brain Volumetry Software for MRI.”)
In regard to study limitations, the authors conceded that the reviewed studies in the meta-analysis did not control for substance abuse, which is associated with adversity exposure. The researchers also noted the majority of studies looking at deprivation with brain function do not report data on whole brain coordinates and were excluded from the meta-analysis. While the study authors utilized DSM-5 criterion A type trauma to categorize adversity type, they noted a lack of clarity as to whether these traumas were present or not in the meta-analysis cohort.