Hippocampal Volumes in Patients With Chronic Combat-Related Posttraumatic Stress Disorder: A Systematic Review

Recent research has demonstrated that veterans with chronic combat-related posttraumatic stress disorder (PTSD) have a twofold increased risk of developing dementia. This review of current literature details neuroanatomical differences between veterans with PTSD and control subjects, some of whom have also had combat experience. The most common and consistent difference was in size of the hippocampus, which was found to be smaller in PTSD patients. There is a hypothesis that smaller hippocampal area is associated with greater risk for dementia; however, an alternate hypothesis is that a smaller hippocampus predisposes to PTSD.

The authors and others have recently demonstrated that veterans with chronic combat-related PTSD (CR-PTSD) have a twofold increased risk of dementia. To understand this increased incidence, they performed a systematic review of the literature on neuroanatomical differences between veterans with chronic CR-PTSD and control subjects (22 included studies). The hippocampus was most commonly and consistently reported to differ between groups, thereby suggesting the hypothesis that PTSD is associated with smaller hippocampi, which increases the risk for dementia. However, an alternate hypothesis is that smaller hippocampal volumes are a preexisting risk factor for PTSD and dementia. Studies are clearly needed to differentiate between these important possibilities.