J Douglas Bremner1, Matthew Hoffman2, Nadeem Afzal2, Faiz A Cheema3, Olga Novik3, Ali Ashraf2, Marijn Brummer4, Ahsan Nazeer2, Jack Goldberg5, Viola Vaccarino6. 1. Departments of Psychiatry and Behavioral Sciences, USA; Radiology, and Medicine (Cardiology), USA; Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, USA. Electronic address: jdbremn@emory.edu. 2. Departments of Psychiatry and Behavioral Sciences, USA. 3. Departments of Psychiatry and Behavioral Sciences, USA; The Vietnam Era Twin Registry, Seattle Veterans Administration Epidemiology Research, USA. 4. Radiology, and Medicine (Cardiology), USA. 5. Information Center and Department of Epidemiology, University of Washington, Seattle, WA, USA. 6. Emory University School of Medicine, Atlanta GA; Atlanta VAMC, Decatur, GA, USA; The Vietnam Era Twin Registry, Seattle Veterans Administration Epidemiology Research, USA.
Abstract
BACKGROUND: Studies using structural magnetic resonance imaging (MRI) volumetrics showed smaller hippocampal volume in patients with post-traumatic stress disorder (PTSD). These studies were cross-sectional and did not address whether smaller volume is secondary to stress-induced damage, or whether pre-existing factors account for the findings. The purpose of this study was to use a co-twin case control design to assess the relative contribution of genetic and environmental factors to hippocampal volume in PTSD. METHODS: Monozygotic (N = 13 pairs) and dizygotic (N = 21 pairs) twins with a history of Vietnam Era military service, where one brother went to Vietnam and developed PTSD, while his brother did not go to Vietnam or develop PTSD, underwent MR imaging of the brain. Structural MRI scans were used to manually outline the left and right hippocampus on multiple coronal slices, add the areas and adjust for slice thickness to determine hippocampal volume. RESULTS: Twins with Vietnam combat-related PTSD had a mean 11% smaller right hippocampal volume in comparison to their twin brothers without combat exposure or PTSD (p < .05). There was no significant interaction by zygosity, suggesting that this was not a predisposing risk factor or genetic effect. CONCLUSIONS: These findings are consistent with smaller hippocampal volume in PTSD, and suggest that the effects are primarily due to environmental effects such as the stress of combat.
BACKGROUND: Studies using structural magnetic resonance imaging (MRI) volumetrics showed smaller hippocampal volume in patients with post-traumatic stress disorder (PTSD). These studies were cross-sectional and did not address whether smaller volume is secondary to stress-induced damage, or whether pre-existing factors account for the findings. The purpose of this study was to use a co-twin case control design to assess the relative contribution of genetic and environmental factors to hippocampal volume in PTSD. METHODS: Monozygotic (N = 13 pairs) and dizygotic (N = 21 pairs) twins with a history of Vietnam Era military service, where one brother went to Vietnam and developed PTSD, while his brother did not go to Vietnam or develop PTSD, underwent MR imaging of the brain. Structural MRI scans were used to manually outline the left and right hippocampus on multiple coronal slices, add the areas and adjust for slice thickness to determine hippocampal volume. RESULTS: Twins with Vietnam combat-related PTSD had a mean 11% smaller right hippocampal volume in comparison to their twin brothers without combat exposure or PTSD (p < .05). There was no significant interaction by zygosity, suggesting that this was not a predisposing risk factor or genetic effect. CONCLUSIONS: These findings are consistent with smaller hippocampal volume in PTSD, and suggest that the effects are primarily due to environmental effects such as the stress of combat.
Authors: Kerry J Ressler; Sabina Berretta; Vadim Y Bolshakov; Isabelle M Rosso; Edward G Meloni; Scott L Rauch; William A Carlezon Journal: Nat Rev Neurol Date: 2022-03-29 Impact factor: 44.711