Startle Reactivity and Peritraumatic Dissociations in Acute Stress Disorder

Startle reactions and their relationship to dissociative symptoms were assessed in acute stress disorder (ASD) patients. Electromyographic (EMG) responses, heart-rate reactions (HRR), and skin conductance responses (SCR) to startle stimuli were compared between victims of mixed traumatic events (n = 31) and healthy controls without trauma exposure (n = 20). All ASD patients met criteria for acute stress disorder (although 12 of them did not demonstrate the required number of dissociative symptoms). Compared to controls, ASD patients showed increased HRR and slower habituation, as well as increased SCRs to the startle stimuli. There were no significant group differences in relation to EMG responses. In ASD patients, reported intensity of peritraumatic dissociations was related to lower EMG startle magnitude and more rapid EMG habituation, suggesting a protective mechanism of dissociative symptoms that may come into effect in response to arousing situations and stimuli.