The environment contributes more than genetics to smaller hippocampal volume in Posttraumatic Stress Disorder (PTSD).
J Douglas Bremner, Matthew Hoffman, Nadeem Afzal, Faiz A Cheema, Olga Novik, Ali Ashraf, Marijn Brummer, Ahsan Nazeer, Jack Goldberg, Viola Vaccarino
Author Information
J Douglas Bremner: 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.
Matthew Hoffman: Departments of Psychiatry and Behavioral Sciences, USA.
Nadeem Afzal: Departments of Psychiatry and Behavioral Sciences, USA.
Faiz A Cheema: Departments of Psychiatry and Behavioral Sciences, USA; The Vietnam Era Twin Registry, Seattle Veterans Administration Epidemiology Research, USA.
Olga Novik: Departments of Psychiatry and Behavioral Sciences, USA; The Vietnam Era Twin Registry, Seattle Veterans Administration Epidemiology Research, USA.
Ali Ashraf: Departments of Psychiatry and Behavioral Sciences, USA.
Marijn Brummer: Radiology, and Medicine (Cardiology), USA.
Ahsan Nazeer: Departments of Psychiatry and Behavioral Sciences, USA.
Jack Goldberg: Information Center and Department of Epidemiology, University of Washington, Seattle, WA, USA.
Viola Vaccarino: Emory University School of Medicine, Atlanta GA; Atlanta VAMC, Decatur, GA, USA; The Vietnam Era Twin Registry, Seattle Veterans Administration Epidemiology Research, USA.
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.
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