data was provided by a larger , ongoing , longitudinal study of rape victims who presented at a center for rape victims ( crv ) at the university hospital , aarhus , denmark . four hundred and eighty - four participants were administered the asds between two and three weeks post - rape . however , eight cases were missing > 20% and thus were excluded from the analysis , leaving an effective sample size of 476 . three hundred and twenty - six ( 68.5% ) participants met the dsm - iv criteria for each of the four symptom clusters . mean scores for symptom clusters were 17.90 ( sd=3.2 , range : 11 to 25 ) , 12.87 ( sd=3.3 , range : 6 to 20 ) , 13.29 ( sd=3.2 , range : 620 ) , and 21.35 ( sd=4.7 , range : 10 to 30 ) , dissociation , intrusion , avoidance , and arousal respectively . 60 ) and all but one participant was female . for further details about the study the second sample comprised 152 bank employees exposed to bank robberies committed in denmark between september 2008 and march 2010 . participants were recruited through a network of crisis intervention specialists contracted with bank organizations in denmark . however , three cases were missing > 20% and thus were excluded from the analysis , leaving an effective sample size of 149 . a total of 25 ( 16.8% ) participants met the dsm - iv criteria for each of the four symptom clusters . mean scores for symptom clusters were 16.68 ( sd=3.6 , range : 11 to 23 ) , 13.56 ( sd=3.3 , range : 9 to 20 ) , 10.32 ( sd=2.8 , range : 6 to 16 ) , and 21.92 ( sd=5.3 , range : 10 to 30 ) for dissociation , intrusion , avoidance , and arousal respectively . data was provided from a national study of bank robberies committed in denmark from april 2010 to april 2011 . the study was conducted in collaboration between the danish bankers association , all danish banks , and the university southern of denmark . a total of 450 participants were administered the asds of which 53 ( 11.8% ) participants met the dsm - iv criteria for each of the four symptom clusters . mean scores for symptom clusters were 17.02 ( sd=2.8 , range : 12 to 24 ) , 12.36 ( sd=3.4 , range : 7 to 20 ) , 10.11 ( sd=3.2 , range : 618 ) , and 20.25 ( sd=4.4 , range : 1030 ) for dissociation , intrusion , avoidance , and arousal respectively . ( in press ) . collectively , a total of 404 participants met the dsm - iv criteria for each of the four asd clusters ( please refer to the measure section for further detail ) . the mean scores on the asds dissociative , intrusion , avoidance , and arousal subscales were 17.7 ( sd=3.2 , range : 11 to 25 ) , 16.3 ( sd=3.6 , range : 9 to 25 ) , 12.7 ( sd=3.4 , range : 6 to 20 ) , and 21.2 ( sd=4.7 , range : 1030 ) , respectively . the asd latent structure was assessed using the danish version of the acute stress disorder scale in all three samples ( asds ; bryant et al . , 2000).the asds is a 19 item self - report scale with four subscales assessing the four separate symptom clusters ; dissociation , re - experiencing , avoidance , and arousal as specified by the dsm - iv . questions are answered on a five - point likert scale ( 1 = not at all , 5 = very much ) . the asd symptom clusters were met if the participants endorsed at least one re - experiencing symptom , one avoidance symptom , and one arousal symptom in addition to at least three dissociative symptoms , all indicated by item scores  3 on the asds . previous studies have used this procedure and have reported good reliability , with reliability coefficients of .85 , .90 , .93 , and .96 ( armour et al . , 2011 ; elklit & christiansen , 2010 ; hansen , in press ; hansen & elklit , 2011 ) for the total scale . the reliability coefficient in the current study for the full combined sample was satisfactory ( total scale=.76 ) . nominal amounts of item - level missing data were present ( < 4 items ) thus maximum likelihood ( ml ) estimation procedures were implemented ( graham , 2009 ) prior to the merging of the three separate samples . all analyses were conducted using mplus 6 software ( muthn & muthn , 2010 ) . we specified and estimated four competing models ( see table 1 . for asds item distributions ) . assumptions of univariate ( no skewness / kurtosis values > 1.35 ) and multivariate ( mahalanobis d ) were met thus we used maximum likelihood estimation in cfa . when specifying the models , the first item in each latent factor was fixed to 1 . in addition , we allowed all factors to correlate but we did not allow for correlated errors . thus , we inspected the chi - square (  ) , the comparative fit index ( cfi : bentler , 1990 ) , tucker  lewis index ( tli : tucker & lewis , 1973 ) , the root mean square error of approximation ( rmsea : steiger , 1990 ) , and the bayesian information criterion ( bic : schwarz , 1978 ) . adequate model fit is demonstrated by a non - significant  , cfi 's and tli 's between .90 and .94 and rmsea 's < .08 . excellent model fit is indicated by cfi 's and tli's>.95 , and rmsea 's < .06 ( hu & bentler , 1999 ) . raftery ( 1995 ) reported that superior model fit is indicated by a 10-point bic difference , which represents a 150:1 likelihood that the model with the lower bic value fits best ( p < .05 ) . additionally , given that fan and sivo ( 2009 ) reported that it is inaccurate to compare nested models on the basis of fit indices alone , we compared nested models using chi - squared difference tests by employing the mplus difftest function ( muthn & muthn , 2006 ) . as chi - square difference testing can not be conducted for non - nested models comparisons data was provided by a larger , ongoing , longitudinal study of rape victims who presented at a center for rape victims ( crv ) at the university hospital , aarhus , denmark . four hundred and eighty - four participants were administered the asds between two and three weeks post - rape . however , eight cases were missing > 20% and thus were excluded from the analysis , leaving an effective sample size of 476 . three hundred and twenty - six ( 68.5% ) participants met the dsm - iv criteria for each of the four symptom clusters . mean scores for symptom clusters were 17.90 ( sd=3.2 , range : 11 to 25 ) , 12.87 ( sd=3.3 , range : 6 to 20 ) , 13.29 ( sd=3.2 , range : 620 ) , and 21.35 ( sd=4.7 , range : 10 to 30 ) , dissociation , intrusion , avoidance , and arousal respectively . 60 ) and all but one participant was female . for further details about the study the second sample comprised 152 bank employees exposed to bank robberies committed in denmark between september 2008 and march 2010 . participants were recruited through a network of crisis intervention specialists contracted with bank organizations in denmark . however , three cases were missing > 20% and thus were excluded from the analysis , leaving an effective sample size of 149 . a total of 25 ( 16.8% ) participants met the dsm - iv criteria for each of the four symptom clusters . mean scores for symptom clusters were 16.68 ( sd=3.6 , range : 11 to 23 ) , 13.56 ( sd=3.3 , range : 9 to 20 ) , 10.32 ( sd=2.8 , range : 6 to 16 ) , and 21.92 ( sd=5.3 , range : 10 to 30 ) for dissociation , intrusion , avoidance , and arousal respectively . data was provided from a national study of bank robberies committed in denmark from april 2010 to april 2011 . the study was conducted in collaboration between the danish bankers association , all danish banks , and the university southern of denmark . a total of 450 participants were administered the asds of which 53 ( 11.8% ) participants met the dsm - iv criteria for each of the four symptom clusters . mean scores for symptom clusters were 17.02 ( sd=2.8 , range : 12 to 24 ) , 12.36 ( sd=3.4 , range : 7 to 20 ) , 10.11 ( sd=3.2 , range : 618 ) , and 20.25 ( sd=4.4 , range : 1030 ) for dissociation , intrusion , avoidance , and arousal respectively . ( in press ) . collectively , a total of 404 participants met the dsm - iv criteria for each of the four asd clusters ( please refer to the measure section for further detail ) . the mean scores on the asds dissociative , intrusion , avoidance , and arousal subscales were 17.7 ( sd=3.2 , range : 11 to 25 ) , 16.3 ( sd=3.6 , range : 9 to 25 ) , 12.7 ( sd=3.4 , range : 6 to 20 ) , and 21.2 ( sd=4.7 , range : 1030 ) , respectively . data was provided by a larger , ongoing , longitudinal study of rape victims who presented at a center for rape victims ( crv ) at the university hospital , aarhus , denmark . four hundred and eighty - four participants were administered the asds between two and three weeks post - rape . however , eight cases were missing > 20% and thus were excluded from the analysis , leaving an effective sample size of 476 . three hundred and twenty - six ( 68.5% ) participants met the dsm - iv criteria for each of the four symptom clusters . mean scores for symptom clusters were 17.90 ( sd=3.2 , range : 11 to 25 ) , 12.87 ( sd=3.3 , range : 6 to 20 ) , 13.29 ( sd=3.2 , range : 620 ) , and 21.35 ( sd=4.7 , range : 10 to 30 ) , dissociation , intrusion , avoidance , and arousal respectively . 60 ) and all but one participant was female . for further details about the study the second sample comprised 152 bank employees exposed to bank robberies committed in denmark between september 2008 and march 2010 . participants were recruited through a network of crisis intervention specialists contracted with bank organizations in denmark . however , three cases were missing > 20% and thus were excluded from the analysis , leaving an effective sample size of 149 . a total of 25 ( 16.8% ) participants met the dsm - iv criteria for each of the four symptom clusters . mean scores for symptom clusters were 16.68 ( sd=3.6 , range : 11 to 23 ) , 13.56 ( sd=3.3 , range : 9 to 20 ) , 10.32 ( sd=2.8 , range : 6 to 16 ) , and 21.92 ( sd=5.3 , range : 10 to 30 ) for dissociation , intrusion , avoidance , and arousal respectively . data was provided from a national study of bank robberies committed in denmark from april 2010 to april 2011 . the study was conducted in collaboration between the danish bankers association , all danish banks , and the university southern of denmark . a total of 450 participants were administered the asds of which 53 ( 11.8% ) participants met the dsm - iv criteria for each of the four symptom clusters . mean scores for symptom clusters were 17.02 ( sd=2.8 , range : 12 to 24 ) , 12.36 ( sd=3.4 , range : 7 to 20 ) , 10.11 ( sd=3.2 , range : 618 ) , and 20.25 ( sd=4.4 , range : 1030 ) for dissociation , intrusion , avoidance , and arousal respectively . collectively , a total of 404 participants met the dsm - iv criteria for each of the four asd clusters ( please refer to the measure section for further detail ) . the mean scores on the asds dissociative , intrusion , avoidance , and arousal subscales were 17.7 ( sd=3.2 , range : 11 to 25 ) , 16.3 ( sd=3.6 , range : 9 to 25 ) , 12.7 ( sd=3.4 , range : 6 to 20 ) , and 21.2 ( sd=4.7 , range : 1030 ) , respectively . the asd latent structure was assessed using the danish version of the acute stress disorder scale in all three samples ( asds ; bryant et al . , 2000).the asds is a 19 item self - report scale with four subscales assessing the four separate symptom clusters ; dissociation , re - experiencing , avoidance , and arousal as specified by the dsm - iv . questions are answered on a five - point likert scale ( 1 = not at all , 5 = very much ) . the asd symptom clusters were met if the participants endorsed at least one re - experiencing symptom , one avoidance symptom , and one arousal symptom in addition to at least three dissociative symptoms , all indicated by item scores  3 on the asds . previous studies have used this procedure and have reported good reliability , with reliability coefficients of .85 , .90 , .93 , and .96 ( armour et al . , 2011 ; elklit & christiansen , 2010 ; hansen , in press ; hansen & elklit , 2011 ) for the total scale . the reliability coefficient in the current study for the full combined sample was satisfactory ( total scale=.76 ) . nominal amounts of item - level missing data were present ( < 4 items ) thus maximum likelihood ( ml ) estimation procedures were implemented ( graham , 2009 ) prior to the merging of the three separate samples . all analyses were conducted using mplus 6 software ( muthn & muthn , 2010 ) . assumptions of univariate ( no skewness / kurtosis values > 1.35 ) and multivariate ( mahalanobis d ) were met thus we used maximum likelihood estimation in cfa . when specifying the models , the first item in each latent factor was fixed to 1 . in addition , we allowed all factors to correlate but we did not allow for correlated errors . thus , we inspected the chi - square (  ) , the comparative fit index ( cfi : bentler , 1990 ) , tucker  lewis index ( tli : tucker & lewis , 1973 ) , the root mean square error of approximation ( rmsea : steiger , 1990 ) , and the bayesian information criterion ( bic : schwarz , 1978 ) . adequate model fit is demonstrated by a non - significant  , cfi 's and tli 's between .90 and .94 and rmsea 's < .08 . excellent model fit is indicated by cfi 's and tli's>.95 , and rmsea 's < .06 ( hu & bentler , 1999 ) . raftery ( 1995 ) reported that superior model fit is indicated by a 10-point bic difference , which represents a 150:1 likelihood that the model with the lower bic value fits best ( p < .05 ) . additionally , given that fan and sivo ( 2009 ) reported that it is inaccurate to compare nested models on the basis of fit indices alone , we compared nested models using chi - squared difference tests by employing the mplus difftest function ( muthn & muthn , 2006 ) . as chi - square difference testing can not be conducted for non - nested models comparisons were based on differences in bic values . the mean asds total score for the combined sample who met the dsm - iv diagnostic criteria for all four symptom clusters ( n=404 ) was 64.5 ( sd=10.1 , range : 4090 ) . notably , the  values of all models were statistically significant . however , this should not lead to rejection of models given that chi - square values tend to become non - significant when assessing model fit with samples which have > 200 participants ( current n=404 ) ( schumacher & lomax , 1996 ) . none of the models reached the recommended values of the cfi and tli for adequate ( between .90 and .95 ) or excellent ( > .95 ) fit . the rmsea failed to reach recommended values for adequate or excellent fit for model 1 ; however rmsea values for model 2 and 3 indicated adequate model fit , whereas the rmsea for model 4 indicated excellent model fit . fit indices for the four alternative asd models  , chi - square ; rmsea , root mean square error of approximation ; ci , confidence interval ; cfi , comparative fit index ; tli , tucker as stated above we compared nested models using chi - squared difference tests by employing the mplus difftest function ( muthn & muthn , 2006 ) . model 2 did not fit significantly better than model 3 , change ( 3 , n=404 ) = 10.17 , p=.0172 . however , model 4 fit significantly better than both model 2 , change ( 4 , n=404 ) = 71.29 , p<.000 and model 3 ,  change ( 7 , n=404 ) = 77.33 , p<.000 ( cf . thus , model 4 provided optimal fit to the data compared to alternative models in the current study . therefore , the corresponding standardized factor loadings for the asd dysphoric arousal replication model can be found in table 3 . standardized factor loadings ( standard errors ) for the asd dysphoric arousal model note : all factor loadings were statistically significant ( p<.05 ) . inter - factor correlations for the dysphoric arousal model of asd the correlation which was not significant ( p<.001 ) . the present study is the first study to assess a replication of ptsd 's newest five - factor dysphoric arousal model using asd data . a competing models approach was implemented in which the asd dysphoric arousal model was compared to three alternative asd models , in a combined heterogeneous clinical trauma sample . akin to a burgeoning literature base in relation to the latent structure of ptsd ( reviewed in pietrzak et al . , 2012 ) results suggest that the latent structure of asd , measured by the asds , is best described as a five - factor structure separating the arousal factor into two separate factors of dysphoric arousal and anxious arousal . thus , it appears that watson 's ( 2005 ) distinction between arousal related to general distress ( i.e. , dysphoric arousal ) and arousal related to fear - based symptoms ( i.e. , anxious arousal ) in relation to ptsd also holds for acute posttraumatic symptoms . hence , it is possible that arousal symptoms play a similar role in both early and long term posttraumatic responding . the pronounced role of arousal symptoms in posttraumatic symptomatology is highlighted in schell , marshall , and jaycox 's ( 2004 ) prospective study of the relationship between ptsd symptom clusters in victims of community violence . 2004 ) found that arousal strongly influenced the other symptom clusters , but at the same time arousal was generally not influenced back by the other symptom clusters . furthermore , arousal was found to be the best predictor of subsequent ptsd symptom severity compared to alternative ptsd symptom clusters . indeed , schell et al . ( 2004 ) found that those with the most pronounced acute arousal symptoms were ( m=9.55 days after hospital admission ) also those who showed the least symptom improvement across a 12 month period . thus , the role of arousal appears pronounced in both early and long term posttraumatic symptomatology . thus , it is also pertinent to differentiate between different forms of arousal both in relation to asd and ptsd . given that the proposed dysphoric arousal model separates the original hyperarousal factor , it is important to investigate the inter - factor correlations . with this in mind , the current study found a certain degree of orthogonality between the dysphoric arousal and anxious arousal factors ( r=.49 ) of the asd dysphoric arousal model . indeed , this finding is contrary to that of some ptsd factor analytic studies , which have previously ( but not always ) reported high inter - factor correlations between dysphoric arousal and anxious arousal ( armour et al . , 2012 ) . however , a moderate correlation between these two factors adds strength to the rationale behind their separation ( cf . interestingly , separating the original arousal factor into dysphoric arousal and anxious arousal resulted in a non - significant correlation between the latter and avoidance . one possible explanation for this is that avoidant coping may theoretically and practically overlap with the ptsd avoidance factor , in that avoidance symptoms may act as coping processes for alternative posttraumatic symptomatology ( as argued by leiner , kearns , jackson , astin & rothbaum , 2012 ) . due to the close similarity between the asd and the ptsd avoidance items and factor , this overlap is likely also apparent between asd avoidance symptoms and avoidant coping behaviors . thus , the lack of a significant correlation between avoidance and anxious arousal in the current study may indicate that avoidance has functioned as a coping mechanism and thus has prevented the development of anxious arousal . indeed , the potentially protective function of the avoidance symptoms may also be indicated by the low to moderate correlations between the avoidance factor and the remaining asd factors in the present study . in accordance with the present study , leiner et al . ( 2012 ) also found that avoidant coping was negatively associated with ptsd severity in treatment seeking rape victims . furthermore , leiner et al . ( 2012 ) found that the association between avoidant coping and ptsd severity was still significant after controlling for initial ptsd severity and after the removal of ptsd avoidance symptoms in order to account for the possible overlap between avoidant coping and ptsd avoidance symptoms . although , the majority of the sample in present study were rape victims , avoidant coping has also previously been found protective against posttraumatic symptoms following robbery ( elklit , 2002 ) . in contrast , however , holahan and moos ( 1987 ) reported that although avoidant emotional coping may be adaptive in the immediate aftermath of trauma , such becomes maladaptive if relied on over a prolonged period of time ( see also olff , langeland & gersons , 2005 ) . indeed , schnider , elhai and gray ( 2007 ) concluded that avoidant coping is one of the best predictors of ptsd severity in college student who had suffered a traumatic loss . notably however , the non - significant correlation is not with hyperarousal specifically , but with a relatively new grouping of symptoms ; anxious arousal . this particular constellation of symptoms is based on fear response rather than anxiety per se , thus the lack of association between avoidance and anxious arousal is , as of yet , unexplored territory . in contrast to the majority of the previous cfa studies ( brooks et al . , 2008 ; hansen et al . the dsm - iv model was not supported in the present study and neither was the armour et al . as mentioned earlier , it is possible that the discrepancy in the previous cfa studies of asd is caused by variation in the form of traumatic exposure or the asd prevalence rates as recently found in relation to ptsd ( biehn et al . , 2012 ) . both are apparent in relation to asd , because the dsm - iv model was found to be the best fit following bank robbery ( hansen et al . , in press ) in a sample of all participants exposed to the trauma , whereas the three - factor model was found to be the best fit following rape ( armour et al . , 2011 ) in a sample were only those participants who met the diagnostic criteria for all four asd symptom clusters was assessed . notably , however the dysphoric arousal model was not tested in previous studies and thus may have provided superior fit in the varying trauma and asd prevalence samples . thus , taking these points and the current results into consideration , the separation of the arousal factor into separate dysphoric and anxious arousal factors may point to an asd model which represents asd 's underlying dimensionality across heterogeneous trauma events better than that of the previous models . the current study is the third ( apart from armour et al . , 2011 ; hansen et al . , in press ) to investigate the fit of the uni - dimensional , one - factor model proposed for the dsm-5 . notably , none of the studies , including this one , have found support for this model over and above alternative models . thus , despite certain discrepancies in factor analytic results related to asd 's latent structure , and despite the only recent ( thus , not fully explored ) proposal that the dysphoric arousal model may represent asd 's latent structure , it is becoming increasingly clear that the current proposal of asd in the dsm-5 seems to be an unsuitable description of acute traumatic stress symptoms . in other words , a growing body of empirical literature highlights the need for accommodating the diagnostic criteria in the dsm-5 . indeed , not doing so may have a serious negative impact , given that assessment and treatment may be based on an imprecise theoretical model . on a more promising note , bryant et al . ( 2011 ) proposed that the inclusion of a wider range of acute reactions in asd in the dsm-5 would result in a more precise conceptualization of asd than previously . however , alternative proposals of asd in the dsm-5 need to be put forward so that they can be tested . limitations of the present study include using a self - report measurement of asd rather than a clinician - administered interview . thus , it is possible that the results reflect properties of the asds rather than the asd diagnosis per se . however , this does seem unlikely , given that the asds items are specifically matched to each of the asd symptoms and given that , unlike previous studies , we used a 100% clinical sample ( i.e. , all participants met diagnostic criteria ) . however , as highlighted by brooks et al . ( 2008 ) it is important to underline that the results should not be interpreted in relation to the utility of the asd diagnosis . it is also important to note that the generalization of these results to alternative trauma populations must be conducted with caution . this is attributable to the fact that although we used a heterogeneous sample of bank robbery and rape victims , the latent structure may vary in trauma populations which have not experienced interpersonal assault . it is also important to note that the large majority of participants in the current study were female , thus the results may not generalize well to male populations , given that gender may also moderate asd 's latent structure . furthermore , we did not assess the individual factors of the asd dysphoric arousal model in relation to external psychopathological constructs . armour et al . , 2012 ) and as such would be an interesting line of enquiry in relation to the asd dysphoric arousal model . moreover , albeit that the dysphoric arousal model was the optimal model compared to alternatives in the current study , model fit was not ideal with excellent model fit only being indicted by the rmsea value and corresponding confidence intervals . in spite of these limitations , the present study represents the first examination of the latent structure of asd in a heterogeneous clinical assault sample . in addition , the present study is based on the largest asd clinical sample thus far . moreover , the present study is the first study to examine a replication of the five - factor dysphoric arousal model of ptsd which separates the arousal factor into dysphoric arousal and anxious arousal factors . the results of the present study suggest that the dimensionality of asd may best be represented as a five factor structure following exposure to two heterogeneous assault types . thus , the current study adds to the debate about how asd should be conceptualized in the pending dsm-5 . future research on asd 's latent structure should further test the dysphoric arousal model across varying forms of traumatic experience . future research may also wish to assess if the asd dysphoric arousal model remains invariant across sub - populations ( i.e. , split by gender , culture , and perhaps diagnostic status ) . there is no conflict of interest in the present study for any of the authors .
backgroundsince the introduction of acute stress disorder ( asd ) into the 4th edition of the diagnostic and statistical manual of mental disorders ( dsm - iv ) research has focused on the ability of asd to predict ptsd rather than focusing on addressing asd 's underlying latent structure . 
 the few existing confirmatory factor analytic ( cfa ) studies of asd have failed to reach a clear consensus regarding asd 's underlying dimensionality . 
 although , the discrepancy in the results may be due to varying asd prevalence rates , it remains possible that the model capturing the latent structure of asd has not yet been put forward . 
 one such model may be a replication of a new five - factor model of ptsd , which separates the arousal symptom cluster into dysphoric and anxious arousal . given the pending dsm-5 , uncovering asd 's latent structure is more pertinent than ever.objectiveusing cfa , four different models of the latent structure of asd were specified and tested : the proposed dsm-5 model , the dsm - iv model , a three factor model , and a five factor model separating the arousal symptom cluster.methodthe analyses were based on a combined sample of rape and bank robbery victims , who all met the diagnostic criteria for asd ( n = 404 ) using the acute stress disorder scale.resultsthe results showed that the five factor model provided the best fit to the data.conclusionsthe results of the present study suggest that the dimensionality of asd may be best characterized as a five factor structure which separates dysphoric and anxious arousal items into two separate factors , akin to recent research on ptsd 's latent structure . 
 thus , the current study adds to the debate about how asd should be conceptualized in the pending dsm-5 .