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a Department of Psychiatry, Massachusetts General Hospital, Boston, Massachusetts, USA b Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, USA c Research Service, VA Medical Center, Manchester, New Hampshire, USA d Neuroimaging Laboratory, Department of Psychiatry, and Surgical Planning Laboratory, MRI Division, Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts, USA e Psychiatry Service, James J. Peters VA Medical Center, Bronx, New York 10468, and Department of Psychiatry, Mt. Sinai School of Medicine, New York 10029, USA
Address for correspondence: Roger K. Pitman, M.D., Massachusetts General Hospital, Room 2616, Bldg. 149, 13th St., Charlestown, MA 02129. Voice: 617-726-5333; fax: 617-726-4078. e-mail: roger_pitman{at}hms.harvard.edu
A biological abnormality found to be associated with posttraumatic stress disorder (PTSD) may be, among other things, a pretrauma vulnerability factor, that is, it may have been present prior to the event's occurrence and increased the individual's likelihood of developing PTSD upon traumatic exposure. Alternately, it may be an acquired PTSD sign, that is, it may have developed after the traumatic exposure, along with the PTSD. We have studied pairs of Vietnam combat veterans and their noncombat-exposed, identical twins in an effort to resolve these competing origins. Combat veterans were diagnosed as current PTSD or non-PTSD (i.e., never had). Average heart rate responses (HRRs) to a series of sudden, loud-tone presentations were larger in Vietnam combat veteran twins with PTSD, but these larger responses were not shared by their noncombat-exposed cotwins, whose responses were similar to those of the non-PTSD combat veterans and their noncombat-exposed cotwins. These results suggest that larger HRRs to sudden, loud tones represent an acquired sign of PTSD. In contrast, increased neurological soft signs (NSSs), diminished hippocampal volume, and presence of abnormal cavum septum pellucidum (CSP) were found in Vietnam combat veteran twins with PTSD and their "high-risk," unexposed cotwins compared to Vietnam combat veteran twins without PTSD and their "low-risk," unexposed cotwins. These results support the conclusion that the latter abnormalities represent antecedent, familial vulnerability factors for developing chronic PTSD upon exposure to a traumatic event.
Key Words: stress disorders • posttraumatic • twins • monozygotic • startle response • neurological examination • magnetic resonance imaging • hippocampus • septum pellucidum This article has been cited by other articles:
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