Posttraumatic stress symptoms (PTSS) are extremely common among childhood cancer survivors (CCS). However, there are individual differences, which may relate to variability in resilience. Previous studies show differential effects of early adversity on the amygdala and hippocampus-brain regions that mediate the stress response and are implicated in the development and/or maintenance of PTSS. Although many children are diagnosed with cancer and other life-threatening illnesses each year, neurobiological correlates of psychological outcomes following medically related adversity remain unclear. This study tests the impact of childhood cancer, cancer-related PTSS, and resilience on amygdala and hippocampal volumes. Amygdala and hippocampal volumes were measured in 24 CCS (11 females, ages 5-17) and 24 age-, sex-, and IQ-matched controls. Cancer-related PTSS and trait resilience were assessed. We also assessed exposure to non-cancer adversities (e.g., bullying) and the parent's cancer-related PTSS. Non-cancer adversities, resilience, and volume of the amygdala and hippocampus were similar between groups. Within CCS, higher cancer-related PTSS was associated with larger right amygdala volumes. More resilient CCS showed larger volumes of the left hippocampus relative to less resilient CCS. Higher parental PTSS was associated with higher PTSS in their child, and CCS reporting more non-cancer adversities showed higher PTSS. However, non-cancer adversities and parent PTSS were not related to regional volumes among CCS. We found distinct effects of resilience and PTSS on amygdala and hippocampal volumes in CCS. Altered development of stress response neural circuitry may be an important neurobiological substrate for understanding psychological outcomes in CCS.

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