Copyright © The British Psychological Society Reproduction in any form (including the internet) is prohibited without prior permission from the Society Brief report Intrusive experiences and hyperarousal in acute stress disorder Sally Hopwood and Richard A. Bryant* University of New South Wales, Sydney, Australia Objective: This study investigated the relationship between hyperarousal, intrusions, and dissociative experiences in acute stress disorder (ASD). Method: Trauma survivors with ASD (n ¼ 30) and without ASD (n ¼ 30) completed either a hyperventilation provocation test (HVPT) or a non-hyperventilating control procedure whilst monitoring intrusive experiences. Participants then completed the Physical Reactions Scale and the Peritraumatic Dissociative Experiences Questionnaire. Results: Whereas the hyperventilation procedure resulted in an increase in the number of intrusions for ASD participants, the hyperventilation procedure resulted in a decrease in the number of intrusions for non-ASD participants. Contrary to expectations, there was no differences in dissociative reactions across group or condition. Conclusions: These findings provide evidence that intrusive phenomenon are directly associated with elevated states of arousal for individuals with ASD. Hyperarousal has been considered a significant factor in the development and maintenance of pathological responses to trauma. Trauma survivors commonly report panic symptoms during the trauma itself, with reported rates varying from 50% (Bryant & Panasetis, 2001) to 90% (Resnick, Falsetti, Kilpatrick, & Foy, 1994). Similarly, ongoing panic attacks are common following the trauma (Falsetti & Resnick, 1997), even in trauma victims without premorbid panic attacks (Nixon & Bryant, 2003). Trauma survivors who develop ASD or subclinical ASD report more peritraumatic panic attacks than those who do not develop ASD (Bryant & Panasetis, 2001). Moreover, longitudinal data indicates that panic is predictive of longer term intrusive, depressive and somatic symptoms at a 3-month follow-up (Resnick et al., 1994). Although not all hyperarousal involves panic, panic attacks in the acute aftermath of trauma exposure do reflect an extreme form of hyperarousal. * Correspondence should be addressed to Richard A. Bryant, School of Psychology, University of New South Wales, NSW 2052, Australia (e-mail: r.bryant@unsw.edu.au). The British Psychological Society 137 British Journal of Clinical Psychology (2006), 45, 137–142 q 2006 The British Psychological Society www.bpsjournals.co.uk DOI:10.1348/014466505X66052