Reduced Hippocampal and Amygdala Volumes as Mechanisms of Stress Sensitization to Depression following Childhood Violence Exposure

Abstract

OBJECTIVE:Stressful life events are more likely to trigger depression among individuals exposed to childhood adversity. However, the mechanisms underlying this stress sensitization remain largely unknown. Any such mechanism must be altered by childhood adversity and interact with recent stressful life events, magnifying their association with depression. This study investigated whether reduced hippocampal and amygdala volumes are mechanisms of stress sensitization following childhood violence exposure. METHODS:A sample of 149 youth (aged 8-17 years), with (N=76) and without (N=73) exposure to physical abuse, sexual abuse, or domestic violence participated. Participants completed a structural MRI scan and were assessed for symptoms of depression. Approximately two years later, stressful life events were assessed along with depression symptoms in 120 participants (57 violence-exposed). RESULTS:Childhood violence exposure was associated with smaller hippocampal and amygdala volumes. Stressful life events occurring during the follow-up period predicted worsening depression over time, and this association was magnified among those with smaller hippocampal and amygdala volumes. Significant moderated mediation models revealed indirect effects of violence exposure on increasing depression over time through hippocampal and amygdala volumes, particularly among youths who experienced more stressful life events. CONCLUSIONS:These results provide novel evidence for reduced hippocampal and amygdala volumes as mechanisms of stress sensitization to depression following exposure to violence.These findings suggest that hippocampal and amygdala-mediated emotional and cognitive processes may contribute to vulnerability to stressful life events following childhood violence exposure.

Smaller Hippocampal Volume among Black and Latinx Youth Living in High-Stigma Contexts

“…For instance, Black youth in the highest-structural stigma states had a hippocampus that was 177 mm 3 smaller than those in the lowest-structural stigma states, equivalent to about 2.3% of the average hippocampal volume among Black youth in the ABCD sample. A recent study, by comparison, found that the reduction in hippocampal volume attributable to childhood experiences of interpersonal violence was 364 mm 3 (64), about 3.8% of the average volume in that sample. To further contextualize this finding, the magnitude of the observed difference in hippocampal size between high and low structural stigma states was equivalent to the predicted impact of a $20,000 difference in annual family income in this sample.…”

Understanding urbanicity: how interdisciplinary methods help to unravel the effects of the city on mental health

“…The metaanalysis included different types of social stressors, some of which are not relevant to urban social risk (e.g., childhood trauma), but is nevertheless informative on the key role for the amygdala in the neural effects of the social environment. Finally, recent evidence linked psychosocial stressors (childhood adversity, migration and urban living) in healthy volunteers to reduced volume of the amygdala (Weissman et al, 2019) and increased connectivity between striatal and cortical regions involved in salience and reward processing (McCutcheon et al, 2019). Interestingly, recent evidence from the animal literature shows that repeated social defeat is associated with sensitized neurons and microglia over several weeks (Weber et al, 2019).…”

“…In addition, evidence from the animal literature shows that repeated social defeat is associated with sensitized neurons and microglia over several weeks (Weber et al, 2019). Such changes at cell level might drive higher-level changes in brain structure, and could contribute to various mental health conditions that have been associated with stress sensitization and reward processing deficits (Gerin, Hanson, Viding, & McCrory, 2019; Weissman et al, 2019; Whitton, Treadway, & Pizzagalli, 2015).…”