Evidence for distinct networks underlying symptom clusters of posttraumatic stress disorder

Background Clinical and psychometric evidence has long supported a multidimensional model of PTSD, with symptom subcategories derived from factor analytic methods. Although research on the biological bases of PTSD as a unitary construct is profuse, comparatively few studies have examined the neural mechanisms underlying subcategories of PTSD symptoms. The present study aimed to provide the first evidence of causal relationships between brain structure and PTSD symptom subcategories, using a lesion-behavior mapping approach. Methods Using a group of male combat veterans with focal penetrating traumatic brain injuries ( n = 177), we determined the effects of focal damage on the PTSD symptom subcategories of hyperarousal, avoidance, and re-experiencing. Results Our findings revealed two distinct networks that underlie symptom subcategories of PTSD: (1) an amygdala-ventromedial prefrontal cortex network underlying hyperarousal and avoidance symptoms, in which amygdala damage acts as a risk factor for the development of these symptoms, while vmPFC damage acts as a protective factor against the same symptoms; and (2) a hippocampal network underlying re-experiencing and avoidance, in which hippocampal damage acts as a protective factor against these symptoms. Conclusions The present study provides novel insights regarding the causal role of key brain regions in the heterogeneous expression of PTSD symptoms. Results not only contribute to a more complete picture of the neural mechanisms underlying PTSD, but may also aid in the future development of individualized therapeutic strategies that target specific symptom profiles.