In the aftermath of trauma, an important challenge involves identifying individuals who will later develop post-traumatic stress disorder (PTSD). ^{Reference Brewin, Rose, Andrews, Green, Tata, McEvedy, Turner and Foa1} The diagnosis of acute stress disorder, which differs from PTSD in its requirement of three or more dissociative symptoms (e.g. derealisation), was introduced to meet this challenge. ^{Reference Harvey and Bryant2,3} The rationale is that dissociation in the acute phase can identify those at risk of later PTSD. ^{Reference Harvey and Bryant2} However, research suggests that dissociation actually accounts for little unique variance in predicting PTSD in adults, ^{Reference Harvey and Bryant4} thus questioning the validity of acute stress disorder. Given the significant concerns about the dissociation mandate in adults, it is important to fully assess whether dissociation has predictive utility in trauma-exposed youth. Our primary aim was therefore to examine the predictive utility of the acute stress disorder dissociation criterion in children and adolescents in a large sample, homogeneous for type of trauma. To this end, we combined data from the three published studies in children and adolescents. ^{Reference Meiser-Stedman, Yule, Smith, Glucksman and Dalgleish5–Reference Kassam-Adams and Winston7} Our second aim was to examine whether individual symptom counts across the different acute stress disorder/PTSD symptom criteria assessed in the month post-trauma can perform as well as full acute stress disorder in predicting later PTSD in children and adolescents.

Method

Data from hospital-attending, trauma-exposed child and adolescent road traffic accident survivors (n=367, 117 female) aged 6–17 years (mean=11.88, s.d.=2.60) were pooled from three centres: Oxford (n=86, aged 6–17 years); ^{Reference Bryant, Mayou, Wiggs, Ehlers and Stores6} London (n=41, aged 10–16); ^{Reference Meiser-Stedman, Yule, Smith, Glucksman and Dalgleish5} and Philadelphia (n=240, aged 8–17). ^{Reference Kassam-Adams and Winston7} Written, informed consent was obtained from caregivers and assent from children. Of the 367 individuals, 285 were followed up at 6 months (n=82, n=29 and n=174 respectively). Participant recruitment and flow details are presented elsewhere. ^{Reference Meiser-Stedman, Yule, Smith, Glucksman and Dalgleish5–Reference Kassam-Adams and Winston7} Diagnoses were based on widely used instruments with robust psychometrics, as follows. Acute stress disorder was assessed at 2–4 weeks (baseline) using either structured clinical interview (London), the Child Acute Stress Questionnaire ^{Reference Winston, Kassam-Adams, Vivarelli-O'Neill, Ford, Newman, Baxt, Stafford and Cnaan8} (Philadelphia), or a combination of questionnaire and interview (Oxford). At 6 months PTSD was assessed using the Anxiety Disorder Interview Schedule, ^{Reference Silverman and Albano9} the Clinician-Administered PTSD Scale for Children and Adolescents, ^{Reference Nader, Kriegler, Blake, Pynoos, Newman and Weathers10} or the Childhood PTS Reaction Index ^{Reference Nader and Stamm11,Reference Pynoos, Frederick, Nader, Arroyo, Steinberg, Eth, Nunez and Fairbanks12} respectively.

Results

At baseline 9% (n=33; 16 females) of the pooled sample met criteria for acute stress disorder and 23% (n=83; 38 females) for sub-acute stress disorder (acute stress disorder minus dissociation), with 7% (n=25; 12 females) meeting criteria for PTSD at 6 months. Point-biserial correlations revealed no significant associations between age and presence of these diagnoses (P>0.4). As initial analyses revealed no significant effects involving research centre (coded by dummy variables) (P>0.2) reported analyses utilised the pooled sample.

As expected, baseline presence of acute stress disorder correlated significantly with 6-month PTSD (φ(283)=0.18, P<0.01). Stepwise logistic regression predicting 6-month PTSD, with subacute stress disorder on step 1 and the acute stress disorder dissociation criterion on step 2, revealed sub-acute stress disorder as a significant predictor of PTSD (Wald=22.39, P<0.001), whereas dissociation provided no significant increment in PTSD prediction (Wald=0.48, P>0.48).

Table 1 shows the ability of different baseline acute stress disorder/PTSD symptom counts to predict PTSD at follow-up. In adult violent crime victims, six or more baseline symptoms of hyperarousal and/or re-experiencing predicted later PTSD as effectively as did full acute stress disorder, in terms of the trade-off between specificity and sensitivity. ^{Reference Brewin, Rose, Andrews, Green, Tata, McEvedy, Turner and Foa1} It is clear from Table 1 that this threshold, and even a threshold of three or more re-experiencing symptoms, was if anything, somewhat better than the full acute stress disorder diagnosis in its balance of sensitivity and specificity for the present sample. Furthermore, adding full acute stress disorder (on step 2) to either of these symptom counts on step 1 in logistic regressions, to predict later PTSD, provided no significant independent predictive benefits for acute stress disorder (Wald=0.71, P>0.4) over and above the predictive effects of either symptom threshold alone (Wald>14.34, P<0.001).

Table 1 Ability to predict PTSD at 6 months by varying acute stress disorder/PTSD symptom counts at 2-4 weeks

Criterion and number of symptoms required for diagnosis	Correctly classified, %	Sensitivity a	Specificity b	Positive predictive power c	Negative predictive power d
Acute stress disorder dissociation
At least one symptom	41	0.85	0.37	0.12	0.96
At least two symptoms	68	0.50	0.70	0.14	0.93
At least three symptomse	80	0.35	0.84	0.18	0.93
At least four symptoms	86	0.19	0.93	0.22	0.92
At least five symptoms	89	0.04	0.98	0.17	0.91
Acute stress disorder/PTSD
Re-experiencing
At least one symptome	51	0.85	0.48	0.14	0.97
At least two symptoms	73	0.73	0.73	0.22	0.96
At least three symptoms	85	0.42	0.89	0.28	0.94
At least four symptoms	91	0.15	0.98	0.50	0.92
Avoidance
At least one symptome	48	0.81	0.44	0.13	0.96
At least two symptoms	72	0.54	0.74	0.17	0.94
Hyperarousal
At least one symptome	44	1.00	0.38	0.14	1.00
At least two symptoms	61	0.77	0.59	0.16	0.96
At least three symptoms	75	0.73	0.75	0.23	0.96
At least four symptoms	82	0.38	0.86	0.22	0.93
At least five symptoms	86	0.19	0.92	0.20	0.92
At least six symptoms	90	0.15	0.98	0.44	0.92
At least 6 re-experiencing or hyperarousal symptomsf	82	0.48	0.85	0.24	0.94
Sub-acute stress disorder	79	0.68	0.80	0.25	0.96
Acute stress disorder full diagnosis	87	0.24	0.93	0.26	0.93

Discussion

The acute stress disorder dissociation criterion appears to have no unique role in the prediction of later PTSD in a large sample of young trauma survivors, homogeneous for trauma type. The significant association between acute stress disorder and later PTSD may therefore simply reflect persistence or chronicity in the symptom clusters that acute stress disorder and PTSD have in common. Indeed, sub-acute stress disorder (acute stress disorder minus dissociation) was almost three times more sensitive than full acute stress disorder in predicting PTSD (Table 1). Thus, these data cast doubt on the predictive validity of the acute stress disorder diagnosis in younger people.

Presence of three or more re-experiencing symptoms at baseline was as effective at predicting later PTSD as the full acute stress disorder diagnosis, and possibly better. Indeed, the full diagnosis provided no significant increment in PTSD prediction over and above this simple threshold. Similar results were found for a count of six or more hyperarousal/re-experiencing symptoms. However, sensitivities for both of these thresholds were less than 50%, suggesting that they are not an effective screen.

Study limitations are that diagnoses were derived differently across the three centres on samples with different age ranges and the focus on a single-incident civilian trauma.