Do Morphological Differences in Brain Structures in PTSD Arise from a Familial Predisposition or from the Disorder Itself?
Staples, Lindsay Katharine
- The cingulate cortex, the hippocampus, and the amygdala have each been implicated in posttraumatic stress disorder (PTSD). This study examines morphological differences in these regions of interest in monozygotic twins discordant for trauma exposure and PTSD. We hypothesized that reduced volumes in the cingulate would represent acquired characteristics of PTSD and that reduced volumes in the ... read morehippocampus would represent a familial predisposition to the disorder. Subjects included identical twin pairs in which (1) the combat-exposed co-twin developed PTSD and the combat-unexposed co-twin did not; and (2) the combat-exposed co-twin never developed PTSD and the combat-unexposed cotwin also did not have PTSD. Differences between PTSD pairs and control pairs will indicate a familial predisposition to abnormalities in the cingulate, hippocampus, and amygdala. Differences between trauma-exposed and unexposed subjects will reflect characteristics acquired after trauma. If individuals with PTSD show significantly different volumes from their brothers as well as from subjects in control pairs, it will indicate that these brain abnormalities are an acquired characteristic of the disorder. In the right rostral and right dorsal anterior cingulate, we found main effects of PTSD Diagnosis in which PTSD twin pairs had larger volumes than non-PTSD pairs. In the right rACC, there was a PTSD Diagnosis x Exposure interaction in the rACC indicating that larger right rACC volumes may be an acquired characteristic of PTSD. Subjects with PTSD but not their brothers had significantly larger right rACC volumes than combat-exposed and unexposed controls. There was an inconsistent result in the left dACC that showed greater volumes in non-PTSD pairs. We also found larger posterior cingulate thickness non-PTSD pairs than PTSD pairs. There was also a main effect of Exposure in the right posterior cingulate with unexposed subjects showing larger volumes than exposed subjects. There was a main effect of Exposure in the right hippocampus in which exposed subjects exhibited larger volumes than unexposed subjects. There were no significant effects in the amygdala. These findings overall did not support our hypotheses and conflict with previous literature on these regions of interest. These results require replication, however may be explained by low symptom severity, effects of treatment, or may demonstrate abnormalities found in unremitting forms of PTSD. The mixed results found in this investigation point to the need for further study of structural differences in these regions of interest.read less