EFFECTS OF EXPERIMENTAL CONTEXT AND EXPLICIT THREAT CUES ON ACOUSTIC STARTLE IN VIETNAM VETERANS WITH POSTTRAUMATIC-STRESS-DISORDER

Background: The hypothesis that exaggerated startle in Vietnam veteran s with posttraumatic stress disorder (PTSD) reflects an anxiogenic res ponse to stressful contexts was rested. Methods: Thirty-four nonmedica ted Vietnam veterans with PTSD, and 17 combat and 14 civilian non-PTSD controls participated in two testing sessions over separate days. Aco ustic startle stimuli were delivered alone or in a test of prepulse in hibition. In the first session, startle was assessed without experimen tal stress. lit the second session, startle was investigated during a stressful ''threat of shock'' experiment, when subjects anticipated th e administration of shocks during threat periods and during safe perio ds when no shocks were anticipated. Results: The magnitude of startle did not differ significantly among the three groups in the first sessi on, but was increased throughout the threat of shock experiment in the PTSD veterans in the second session. The actual increase in startle i n the threat compared to the safe condition did not significantly diff er among the three groups. Prepulse inhibition was reduced in the PTSD veterans, compared to the non-PTSD civilians, but not compared to the non-PTSD veterans. Conclusion: Exaggerated stat-tie in Vietnam vetera ns with PTSD reflects an anxiogenic response to an environment that is experienced as stressful. (C) 1998 Society of Biological Psychiatry.