Post‐traumatic stress disorder (PTSD) is often characterized by deficits in memory encoding and retrieval and aberrant fear and extinction learning. The hippocampus plays a critical role in memory and contextual processing and has been implicated in intrinsic functional connectivity networks involved in self‐referential thought and memory‐related processes. This review focuses on hippocampal activation findings during memory and fear and extinction learning tasks, as well as resting state hippocampal connectivity in individuals with PTSD. A preponderance of functional neuroimaging studies to date, using memory, fear learning, and extinction tasks, report decreased or “controls comparable” hippocampal activation in individuals with PTSD, which is usually associated with poorer performance on the task imaged. Existing evidence thus raises the possibility that greater hippocampal recruitment in PTSD participants may be required for similar performance levels. Studies of resting state functional connectivity in PTSD predominantly report reduced within‐network connectivity in the default mode network (DMN), as well as greater coupling between the DMN and salience network (SN) via the hippocampus. Together, these findings suggest that deficient hippocampal activation in PTSD may be associated with poorer performance during memory, extinction recall, and fear renewal tasks. Furthermore, studies of resting state connectivity implicate the hippocampus in decreased within‐network DMN connectivity and greater coupling with SN regions characteristic of PTSD.

There has been extensive research conducted on how stressful events and traumas are associated with depression and post-traumatic stress symptoms. However, very little research has investigated the association between exposure to stressful events/traumas and depressive and post-traumatic symptoms in a healthy, nonclinical population of adults. Our study examined relationships between exposure to stressful events/traumas, posttraumatic stress, and depression symptoms in a healthy, nonclinical sample of adults. While participants did not meet diagnostic criteria for posttraumatic stress disorder (PTSD) or depression, our results suggest a positive relationship between the number of different lifetime stressful events/traumas reported and both depressive and post-traumatic stress symptoms. These findings suggest that people who experience a greater variety of different stressful events/traumas during their lives report greater depressive and post-traumatic stress symptoms in response to those events.