vidence for Acquired Pregenual Anterior Cingulate ray Matter Loss from a Twin Study of Combat-Rela osttraumatic Stress Disorder

ackground: Controversy exists over the nature and origin of reduced regional brain volumes in posttraumatic stress disorder (P ssue is whether these reductions represent preexisting vulnerability factors for developing PTSD upon traumatic exposure or acquir igns due to the traumatic stress that caused the PTSD or the chronic stress of having the disorder (or both). We employed a ca esign in monozygotic twin pairs discordant for combat exposure to address the preexisting versus acquired origin of brain morp bnormalities in PTSD.