BRITISH JOURNAL OF PSYCHIATRY !2002), 180, 363^368

Dissociation and post-traumatic stress disorder: within 24 h of being admitted and invited to participate in the study. Patients who two prospective studies of road traffic had a head injury that led to unconscious- ness were excluded. After complete descrip- tion of the study to the subjects, written accident survivors informed consent was obtained. No patients who were approached declined to JAMES MURRAY, ANKE EHLERS and RICHARD A. MAYOU be interviewed. Patients' mean age was 33.9 years range 18±59, s.d.ˆ12.3). The majority of patients had fractures 81%). Most of them were drivers of vehicles 53%) or motorcyclistsmotorcyclists 32%). The remain- Background Dissociative symptoms Although dissociation has been variously ing patients werepassengers or pedestrians. during trauma predict post-traumatic defined, dissociative symptoms and pro- cesses have been seen as important in Out-patient sample stress disorder PTSD), butthey are often explaining the development of post- A consecutive series of 439 out-patients transient.It is controversial whether they traumaticstress disorder PTSD; Horowitz, who attended the Accident & Emergency predictchronic PTSD over and above 1976; Speigel & Cardena, 1990; van der Department of the John Radcliffe Hospital, whatcan be predicted from other post- Kolk & Fisler, 1995; Foa & Hearst-Ikeda, Oxford, UK, following a road traffic trauma symptoms. 1996). Dissociative symptoms, such as accident were invited to participate in the reduced awareness of one's surroundings, study and sent a questionnaire package. A Aims Toinvestigate prospectively the de-realisation,de-realisation, de-personalisation or emo- total of 176 patients 40%) opted into the relationship between dissociative tional numbing have been shown to predict study and returned questionnaires. There the later development of PTSD in a number symptoms before, during and after a were 79 female patients and 94 male of populations e.g. Koopman et al, 1994; patients on three questionnaires, gender trauma and other psychological Shalev et al, 1996; Ehlers et al, 1998). The was unidentifiable). The mean age of predictors, and chronic PTSD. American Psychiatric Association 1994) respondents was 33.8 years range 17±76, has emphasised the role of dissociation in s.d.ˆ13.3). Respondents were similar to Method Two samples of 27 and176 the newdiagnosis of acute stress disorder the total sample population sent question- road traffic accident survivors were ASD). naires in terms of age and gender recruited. Patients were assessed shortly However, the validity and utility of distribution 58% male, mean age 32.2 requiring dissociative symptoms as a core after the accident and followed at intervals years). feature of ASD is controversial Marshall over the next 6 months. Assessments et al, 1999). It remains unclear howthe Measures includedmeasuresofdissociation, memory predictive power of dissociation compares Symptoms of PTSD fragmentation, data-driven processing, with that of other early symptoms of PTSD Participants completed the Posttraumatic rumination and PTSD symptoms. in the aftermath of trauma, such as re- experiencing Classen et al, 1998; Brewin Diagnostic Scale PDS; Foa et al, 1997) at initial and follow-up assessments. The Results All measures of dissociation, et al, 1999), and with that of other estab- PDS asks participants to rate howmuch particularly persistentdissociation 4 lished psychological predictors of PTSD, for example post-event rumination Ehlers they were bothered by each of the PTSD weeks after the accident, predicted et al, 1998). Furthermore, dissociative symptoms specified in DSM±IV American chronic PTSD severity at 6 months. symptoms are often transient Spiegel & Psychiatric Association, 1994), ranging Dissociative symptoms predicted Cardena, 1990; World Health Organization, from 0 `never') to 3 `5 times per week or more/very severe/nearly always'). The PDS subsequent PTSD over and above the 1992). This raises the question of whether the persistence of dissociative symptoms yields a sum score measuring the overall other PTSD symptom clusters.Memoryclusters. Memory beyond the traumatic event may be a severity of PTSD symptoms. In addition, fragmentation and data-driven processing stronger predictor of PTSD than initial the presence/absence of PTSD is determined also predicted PTSD.Rumination about reactions. by assessing whether a patient endorsed the the accident was among the strongest minimum number of symptoms required by DSM±IV for each of the symptom clusters. predictorsofsubsequent PTSD symptoms. METHOD We used the standard cut-off recommended by Foa et al 1997) for determining the Conclusions Persistent dissociation Subjects presence of a symptom at least `1'ˆ`once and rumination 4 weeks after trauma are In-patient sample a week/once in a while'). more usefulusefulinidentifying in identifying those patients Subjects were 27 21 men and 6 women) whoarelikelytodevelopchronicPTSD patients who were admitted for in-patient Dissociation during the accident and thaninitialreactions.than initial reactions. treatment at the John Radcliffe Hospital, persistent dissociation at 4 weeks Oxford, UK, following a road traffic Dissociation during the accident and con- Declaration of interest None. accident. Patients were visited by J.M. tinued dissociation at 4 weeks were assessed

363 MURR AY ET AL

with the State Dissociation Questionnaire with high scores on the TDQ were more RQ). This is a six-item scale developed by SDQ). This is a seven-item scale developed likely to experience intrusive memories of the authors in a series of studies Murray, by the authors further information avail- an unpleasant videotape than those with 1997; Clohessy & Ehlers, 1999; Steil & able upon request), measuring dissociative lowscores. The in-patient sample com- Ehlers, 2000; Halligan et al, 2002) experiences such as de-realisation, de- pleted the full TDQ and the out-patient assessing ruminative thoughts such as `Do personalisation, detachment, altered time sample completed a short 10-item version you go over what happened again and sense and reduction of awareness in TDQ-s). The TDQ-s correlates highly again?' and `Do you dwell on what surroundings. The scale was developed in with the TDQ rˆ0.94, n1ˆ69 students, happened, without really solving or decid- a series of studies with trauma survivors n2ˆ27 in-patients). In the present studies, ing anything?'. The internal consistencies and student volunteers and shows good the internal consistency for the TDQ in for the RQ in the present samples were reliability and validity Murray, 1997; the in-patient sample was Cronbach's Cronbach's aˆ0.62 nˆ27) and 0.77 Halligan et al, 2002). The internal consis- aˆ0.92 nˆ27) and the retest reliability nˆ173). tencies for the SDQ in the present samples over a 6-month period rˆ0.82 nˆ16). were Cronbach's a factors of 0.75 nˆ27) The internal consistency for the TDQ-s Assessment of ASD and 0.79 nˆ173). in the out-patient sample was Cronbach's aˆ0.86 nˆ176), and the retest reliability Patients were diagnosed as having ASD if they endorsed the minimum number of Pre-accident dissociative tendencies trait over a 6-month period rˆ56 nˆ129). symptoms specified in DSM±IV American dissociation) Psychiatric Association, 1994) as assessed Whether or not individuals dissociate Memory fragmentation with the PDS and SDQ, respectively, and during a traumatic event may depend on Patients rated the degree to which their if they met the disability criterion as mea- individual personality differences in a memory of the accident was fragmented sured by the PDS. In addition to assessing general tendency to dissociate. The Trait `Are your memories of the accident in whether or not patients met diagnostic Dissociation Questionnaire TDQ) devel- any way unclear or jumbled?') on a four- criteria for ASD in the 4 weeks after the oped by the authors further information point scale from `not at all' to `a lot/very accident, we assessed whether they met available upon request) assessed the parti- much'. The in-patient sample also were the symptom criteria but not the duration cipants' pre-accident disposition for dis- asked to provide a narrative of the accident. and disability criteria) for the disorder at sociative experiences. The questionnaire The interviewer J.M.) rated these narra- initial assessment. contains 38 items and was developed from tives for the degree of fragmentation on a a pool of 101 items taken from: four-point scale 0ˆ`very coherent', Injury severity a)existing dissociation measures, in parti- 1ˆ`quite coherent', 2ˆ`not very coherent', For the in-patients and the first 86 partici- cular the widely used Dissociative 4ˆ`very incoherent') without knowledge pants of the out-patient study, Abbreviated Experiences Scale Bernstein & Putnam, of the patients' questionnaire scores. 1986), the Peritraumatic Dissociation Injury Scores AIS) were calculated from Scale Marmar et al, 1994), the Stanford admission notes American Association for Acute Stress Reaction Questionnaire Data-driven processing Automotive Medicine, 1985). Out-patients Koopman et al, 1994) and the Percep- also were asked to rate the degree of their Building on results from experimental tual Alteration Scale Sanders, 1986); injuries on a four-point scale from `not at cognitive psychology, Ehlers & Clark and all' to `a lot/very much'. 2000) suggested that individuals who b)newitems that represented aspects of mainly engage in data-driven processing dissociation considered to be of import- during trauma will be more likely to show Procedure ance for the development of PTSD that deficits in intentional recall of the trauma In-patient sample were not sufficiently represented in the memory and to suffer from subsequent re- existing scales, in particular items Patients were interviewed and they filled experiencing symptoms than those who in the initial questionnaires in hospital measuring emotional numbing Foa & mainly engage in conceptual processing. Hearst-Ikeda, 1996). within 24 h of being admitted. Follow-up Patients in the out-patient study indicated questionnaires were sent by mail at 1, 2 Murray 1997) described data support- the extent to which they had engaged in and 4 weeks and 3 and 6 months after ing the reliability and validity of the ques- data-driven processing `Were you over- the accident. Owing to incomplete return tionnaire. Factor analyses indicated that whelmed by different sensations and rates, a few of the 4-week data were esti- the questionnaire measures seven different impressions?')impressions?') and in conceptual processing mated from the 2-week data for parti- aspects of dissociation, namely detachment `Did you realise that you were in a danger- cipants with a PDS score of 0 at 2 from others and the world, sense of split ous situation?') on a four-point scale from weeks), yielding 21 participants for this self, lability of mood and impulsivity, in- `not at all' to `a lot/very much'. The data- assessment 78%). At the 6-month attention and memory lapses, emotional driven processing score was the difference assessment, 21 patients returned the numbing, confusion and altered sense of between these two items. questionnaires. time and amnesia for important life events. The internal consistency of the total score was Cronbach's aˆ0.93 Rumination Out-patient sample nˆ211) and the retest reliability over a Rumination following the accident was Questionnaires were sent out to patients 2-month period rˆ0.86 nˆ83). Students assessed with the Rumination Questionnaire within 48 h of the accident. The vast

364 DISSOCIATION AND PTSD

TaTable b l e 1 Clinical outcome Further analyses tested whether the patients' reported pre-accident tendency to DiagnosisIn-patients Out-patients dissociate predicted dissociative responses during and after the accident. Dissociation Acute stress disorder: symptom criteria at initial assessment11.1% 24.6% during the accident showed moderate cor- Acute stress disorder during 4 weeks following accident12.5% 10.2% relations with the patients' pre-accident ten-

Post-traumatic stress disorder at 1 month after accident 31.6% 28.3% dency to dissociate rsˆ0.53 and P50.01 Post-traumatic stress disorder at 6 months after accident 19.0% 24.3% for in-patients; rsˆ0.33 and P50.001 for out-patients). Partial correlations showed that, in the out-patient sample but not in the smaller in-patient sample), dis- majority of participants 82%) returned the weeks after the accident. Dissociation at 4 sociation during the accident continued to questionnaires within the first week of the weeks predicted the PTSD severity at 6 correlate with PTSD symptom severity at accident. Follow-up questionnaires were months over and above the initial dissoci- 4 weeks rpˆ0.31, P50.01) and 6 months sent at 4 weeks and 6 months after the ation partial correlations: rpˆ0.63 and rpˆ0.19, P50.05) when pre-accident accident. Return rates were 83% nˆ146) P50.01 for in-patients; rpˆ0.47 and tendency to dissociate was controlled. at 4 weeks and 80% nˆ140) at 6 months. P50.001 for out-patients). Partial correlations between persistent

Data analysis Spearman correlation coefficients were Ta b l e 2 Spearman correlations between predictor variables and subsequent post-traumatic stress disorder calculated because the PDS scores tended 7PTSD) symptom severity to be skewed to the left. For partial corre- lations and multiple regression analyses, MeasurePTSD symptom severity PTSD symptom severity log-transformed PDS scores were used that at 4 weeks at 6 months normalised distributions. Pre-accident dissociative experiences RESULTS In-patients 7TDQ)0.53* 0.48* Out-patients 7TDQ-s) 0.38*** 0.25** Clinical outcome Dissociation during accident Table 1 shows the percentage of patients In-patients 7SDQ)0.41 { 0.30 who met symptom criteria for ASD at Out-patients 7SDQ)0.43*** 0.28*** initial assessment, full criteria for ASD Persistent dissociation at 4 weeks during the first 4 weeks following the In-patients 7SDQ)0.64** accident and criteria for PTSD at the 4- Out-patients 7SDQ)0.55*** weekand 6-month assessments. In the out-patientout-patient sample, 32% of those patients Memory fragmentation at initial assessment who met ASD symptom criteria at initial In-patients 7expert rating)0.41 { 0.58* assessment and 77% of those who met In-patients 7self-report)0.19 0.20 ASD criteria during the 4 weeks following Out-patients 7self-report)0.32*** 0.12 the accident met the PTSD criteria at 6 Persistent memory fragmentation at 4 weeks months. In-patients 7self-report)0.20 Out-patients 7self-report)0.23* Relationship of dissociation and Data-driven processing during accident other predictors with subsequent Out-patients0.26** 0.22* PTSD symptoms Rumination at initial assessment Table 2 shows the relationships between In-patients 7RQ)0.53* 0.47* the dissociation measures, the other cogni- Out-patients 7RQ)0.41*** 0.30*** tive variables, injury severity and PTSD Rumination at 4 weeks severity scores at 4 weeks and 6 months In-patients 7RQ)0.69*** after the accident. Out-patients 7RQ)0.53*** Physical injury 7AIS) Dissociation measures In-patients0.09 0.01 A pre-accident tendency to dissociate as Out-patients0.01 0.01 well as dissociation during the accident pre- Self-rated injury severity dicted the PTSD symptom severity. In the Out-patients0.25** 0.21* long term, however, the dissociation vari- TDQ,Trait Dissociation Questionnaire;TDQ-s, short10-itemshort10-itemversion version of TDQ; SDQ, State Dissociation Questionnaire; able that predicted chronic PTSD symp- RQ, Rumination Questionnaire; AIS, Abbreviated Injury Scale. toms best was persistent dissociation 4 *P50.05, **P50.01, P50.001, {P50.10.

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dissociation at 4 weeks and PTSD severity Rumination about the accident was ASD and PTSD at 6 months, controlling for pre-accident among the strongest predictors of PTSD. The prevalence rates of ASD and PTSD in tendency to dissociate, were significant in In the long term, the rumination variable the present samples have to be interpreted bothsamples r ˆ0.51 and P50.05 for that predicted chronic PTSD symptoms best p with caution because they relied on a self- in-patients;in-patients; r ˆ0.47 and P50.001 for was persistent rumination 4 weeks after the p report questionnaire rather than diagnostic out-patients). accident. It predicted PTSD symptoms at 6 interviews, and the appropriate cut-off for We tested further whether the dissoci- months even when dissociative symptoms scoring symptoms from such question- ation symptom cluster added to the pre- at 4 weeks were controlled for in-patients: naires is still under discussion Brewin et diction of PTSD symptom severity at 6 r ˆ0.56, P50.05; out-patients: r ˆ0.42, p p al, 1999). However, our studies replicate months over and above what could be pre- P50.001). earlier findings on the prevalence of ASD dicted on the basis of the re-experiencing, and PTSD after road traffic accidents avoidance and hyperarousal symptom Blanchard et al, 1996; Ehlers et al, clusters in the first 4 weeks after trauma, Multiple regression 1998; Harvey & Bryant, 1998), support- similar to an analysis of Brewin et al Howmuch of the variance of PTSD symp- ing the validity of the data. Previous 1999). In a hierarchical regression tom severity 6 months after the accident studies have shown that around 80% of analysis, we entered the presence/absence can be explained by dissociation and the patients who have ASD during the 4 weeks of the reliving, avoidance and hyperarousal other cognitive predictors? In a hierarchical following trauma will develop PTSD cluster symptoms in the first step. These multiple regression analysis of the out- Bryant & Harvey, 1998; Harvey & variables predicted 34% of the variance of patient sample, the variables taken at initial Bryant, 1998; Brewin et al, 1999). The re- PTSD severity at 6 months Rˆ0.58, assessment were entered in the first step sults of our out-patient study are com- R2ˆ0.34, adjusted R2ˆ0.32, Fˆ20.98, pre-accident dissociative tendencies, dis- parable but timing of assessment may be d.f.ˆ3, 124, P50.0005). The dissociation sociation and data-driven processing during crucial. The ASD status may fluctuate symptom cluster significantly improved the accident, initial memory fragmentation during the first 4 weeks following trauma the prediction R2 changeˆ0.08, F change and rumination). These variables explained and more persistent ASD may be more 1, 123)ˆ16.97, P50.0005) and the com- 13% of the variance Rˆ0.36, R2ˆ0.13, predictive than initial ASD in predicting bination of all ASD symptom clusters, adjusted R2ˆ0.10, F 5, 116)ˆ3.54, Pˆ PTSD. including dissociation, predicted 42% of 0.005). In the second step, the variables the variance of PTSD symptom severity taken 4 weeks after the accident were Rˆ0.65, R2ˆ0.42, adjusted R2ˆ0.40, F Dissociation as a predictor of PTSD entered, that is, persistent dissociation, 4, 123)ˆ22.00, P50.0005). Similar The present studies indicated that persistent memory fragmentation and rumination. results were obtained when PTSD severity dissociation is a stronger predictor of These variables significantly increased the at 4 weeks was predicted from symptom chronic PTSD than dissociation during the accuracy of the prediction R2 changeˆ0.27, clusters at initial assessment, or when accident. Persistent dissociation at 4 weeks F change 3, 113)ˆ17.43, P50.0005). logistic regression analyses predicting the remained a significant predictor of PTSD Overall, dissociation and the other cognitive presence/absence of PTSD were used. The severity at 6 months when pre-accident predictors explained 41% of the variance of pattern of results did not change when a tendency to dissociate or initialdissociation PTSD symptom severity at 6 months stricter cut-off of `2' was used for scoring was partialled out. This pattern of results Rˆ0.64, R2ˆ0.41, adjusted R2ˆ0.37, F symptoms on the PDS, as in the analysis suggests that although initial dissociation 8, 111)ˆ9.69, P50.0005). of Brewin et al 1999). may put people at risk for PTSD, many are able to compensate by post-event pro- cessing, or only those who continue to dis- Injury severity sociate may be at high risk of persistent Other cognitive predictors Injury severity as measured by the AIS was problems. Memory fragmentation tended to showa not a good predictor of PTSD severity. The patients' reports of their pre- positive relationship with PTSD severity. However, the patients' own ratings of the accident tendency to dissociate correlated The expert rating appeared to be a better severity of their injuries correlated signi- with initial dissociation and subsequent predictor than self-reports of frag- ficantly with PTSD severity at 4 weeks PTSD symptoms. However, in line with mentation. Memory fragmentation self- and 6 months. the results of the retrospective study by reports) correlated with both initial Tichenor et al 1996), the prospective out- dissociation rsˆ0.37, P50.001 for out- patient study found that dissociation during patients) and data-driven processing DISCUSSION the accident predicted PTSD symptoms

rsˆ0.27, P50.001 for out-patients). over and above a pre-accident tendency to Data-driven processing during the acci- The studies reported here used a prospec- dissociate. Thus, the contribution of a dis- dent correlated with PTSD symptoms. tive design and assessed peritraumatic sociative response to trauma on subsequent Partial correlations between data-driven dissociation and other indicators of cog- PTSD appears to be, in part, independent of processing and PTSD symptoms at both nitive processing shortly after the traumatic pre-existing dissociative traits. time points remained significant when dis- event. This represents an advantage over Overall, the studies supported the sociation during the accident was con- many previous studies that estimated pro- importance of dissociation in predicting trolled for 4 weeks: rpˆ0.23, P50.01; 6 cessing during trauma from reports given PTSD. In contrast to the results of Brewin months: rpˆ0.17, P50.05). several weeks or even months later. et al 1999) dissociative symptoms

366 DISSOCIATION AND PTSD

predicted later PTSD symptoms over and above what could be predicted from other CLINICAL IMPLICATIONS PTSD symptoms, such as re-experiencing, avoidance and hyperarousal, even when & Continuing dissociation and rumination 4 weeks after trauma predict chronic the stricter cut-off for scoring the presence post-traumatic stress disorder 7PTSD) better than initial reactions. of PTSD symptoms used by Brewin et al 1999) was used. Further studies will have & Patients with persisting dissociation and rumination are in most need of to clarify whether differences in the popu- treatment. lation studied or methodological differ- ences may have contributed to the & Dissociative symptoms help to predict chronic PTSD over and above what can be different results. predicted from the other PTSD symptom clusters.

LIMITATIONS Other cognitive predictors & Sample size in the in-patient study was small and the response rate in the out- Howdoes dissociation lead to later symp- patient sample was moderate. However, the results cross-validated well. toms of PTSD? One possibility is that dissociative symptoms are a sign of the & The study largely relied on self-report instruments. individual's inability to process fully the traumatic event and its implications Spiegel & Although initial measures were taken very soon after the trauma, some remain & Cardena, 1990; van der Kolk & Fisler, retrospective. 1995; Brewin et al, 1996; Foa & Hearst- Ikeda, 1996; Ehlers & Clark, 2000). In- complete processing may lead to deficits in the memory of the traumatic event, ranging from uncertainty about the sequence of JAMES MURRAY, DPhil, Department of Psychology,University of Surrey,Guildford; ANKE EHLERS, PhD, events and memory fragmentation to Department of Psychology,Institute of Psychiatry,London; RICHARD A. MAYOU,MAYOU,MD,Department MD, Department of Psychiatry,University of Oxford,UKOxford, UK complete dissociative amnesia for the event. Such deficits in trauma memory may be CorrespCorrespondence:ondence: Professor Anke Ehlers,Department of Psychology,Institute of Psychiatry,DePsychiatry,De responsibleresponsible for the easy triggering of Crespigny Park,London SE5 8AF,UK.Tel: 020 7848 5033; fax: 020 7848 0591; e-mail: re-experiencingre-experiencing and hyperarousal symp- [email protected] toms characterising PTSD Brewin et al, 1996; Foa & Hearst-Ikeda, 1996; Ehlers First received 8 June 2001, final revision 3 December 2001, accepted 3 December 2001) & Clark, 2000). To date, only preliminary evidence for this hypothesis is available. Amir et al 1998) have reported that fragmented trauma memories are indeed reliability of global experimenter ratings Ehlers, 1999; Steil & Ehlers, 2000). Both in- correlated with severity of PTSD, and that of memory fragmentation, such as the one itial and persistent rumination at 4 weeks the memories become more coherent with used in the present study, supporting the were strong predictors of chronic PTSD. successful exposure treatment see Foa et validity of the present data. Rumination seems to be a maladaptive cog- al, 1995). Another study reported that The results of the out-patient study are nitive processing style that is quite indepen- survivors of road traffic accidents with in line with Ehlers & Clark's 2000) dent of dissociation. Patients who ruminated ASD gave more disorganised trauma narra- hypothesis on the role of data-driven excessively about questions such as why the tives than those without ASD Harvey & processing during trauma. The significant trauma happened to them, howthey could Bryant, 1999). correlations with memory fragmentation have prevented the trauma or its outcome The present studies are the first to support the hypothesised link between this or howthey could get revenge for what provide prospective evidence for the role processing style and deficits in intentional happened to them were more likely to have of memory fragmentation in PTSD. recall of the trauma memory. As predicted, chronic PTSD symptoms. At this stage, it is Patients' self-reports of memory frag- data-driven processing also predicted sub- unclear what exactly the mechanisms are by mentation may be less reliable indicators sequent PTSD symptoms. The present study which rumination maintains PTSD and in of actual fragmentation than expert ratings, was the first to explore the role of this vari- what ways it differs from helpful exposure which tended to show a stronger relation- able in a prospective study of PTSD, and a to trauma memories. It may prevent patients ship with subsequent PTSD. The present preliminary short measure of data-driven from accepting that the trauma is an event studies used global ratings, and more processing was used. It is therefore en- from the past and may interfere with the for- sophisticated measures may prove more of couraging that Halligan 1999) could repli- mation of more complete trauma memories the trauma memory dysfunction. Halligan cate the relationships between data-driven by focusing on `what if' questions rather 1999) replicated the role of disorganised processing, memory fragmentation and sub- than the experience of the trauma as it trauma memories in the development of sequent PTSD symptoms in a prospective actually happened. It may also directly PTSD following assault using a self-report study of assault survivors. increase feelings of nervous tension, dys- questionnaire and several expert ratings. The results on rumination extend earlier phoria or hopelessness, and cue intrusive The authors also found a high interrater findings Ehlers et al, 1998; Clohessy & memories of the event.

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ACKNOWLEDGEMENTS Classen, C., Koopman, C., Hales, R., et al !19 9 8) Horowitz, M. J. !1976) Stress Response Syndromes.New Acute stress disorder as a predictor of posttraumatic York: Aronson. stress symptoms. American Journal of Psychiatry, 155, The work was conducted at the Department of Psy- Koopman, C., Classen, C. & Speigel, D. !1994) 620^624. chiatry, University of Oxford, UK. The studies were Predictors of posttraumatic stress symptoms among supported by grants from the Medical Research Clohessy, S. & Ehlers, A. !1999) PTSD symptoms and survivors of the Oakland/Berkeley,Calif., firestorm. American Journal of Psychiatry, 151, 888^894. Council and the Wellcome Trust. The authors would coping in ambulance service workers. British Journal of Clinical Psychology, 38,251^266., 251^266. like to thank Gail Stockford for her help with patient Marmar,C. R.,Weiss, D. S., Schlenger,W. E., et al recruitment and Christopher Bulstrode and the Ehlers, A., Mayou, R. A. & Bryant, B. !1998) !19 94) Peritraumatic dissociation and posttraumatic staff of the Accident and Emergency Services at the Psychological predictors of chronic posttraumatic stress stress in male Vietnam theater veterans. American Journal of Psychiatry, 151, 902^907. John Radcliffe Hospital,Oxford, for their support. disorder after motor vehicle accidents. Journal of Abnormal Psychology, 107, 5508^519. 08^519. Marshall, R. D., Spitzer, R. & Liebowitz, M. R. !1999)

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