Subtle neurological deficits appear to predispose some individuals to the development of posttraumatic stress disorder (PTSD) related to combat experiences, according to a report in the Archives of General Psychiatry.Previous studies have linked neurological deficits to PTSD, but it was unclear if the deficits were part of the disorder or they were there before the disorder developed, representing a vulnerability factor, senior author Dr. Roger K. Pitman, from Massachusetts General Hospital in Boston, and colleagues note.To sort this out, the researchers tested for mild neurological deficits or "soft signs" in 25 Vietnam veterans with PTSD, 24 veterans without PTSD, and in the veterans' identical twins who had not been exposed to combat. Forty-five neurological soft signs were evaluated and rated in severity from 0 (none) to 3 (most severe).Neurological soft signs include mild impairments such as altered sense of direction, difficulty identifying objects by sight or touch, difficulty in performing specific tasks and impaired reflexes.Combat veterans with PTSD had higher neurological soft sign scores than veterans without PTSD, a finding consistent with previous reports. However, the unexposed twins of PTSD veterans also had higher neurological soft sign scores than the twins of veterans without PTSD. This suggests that the neurological deficits in PTSD patients preceded the onset of their disorder.Further analysis showed that the higher neurological soft sign scores in the twins of PTSD veterans were not explained by age, other traumatic life events, alcoholism or other psychiatric disorders.The findings clearly support the conclusion that subtle neurological dysfunction in PTSD patients is not associated with PTSD-related brain damage, but instead represents a family vulnerability factor, which was there before exposure to the traumatic combat events, the investigators conclude.