Of the 35 participants, 18 had been shot, stabbed, mugged, or threatened with a weapon and 17 had been badly beaten. Seven victims were hospitalized in surgical units. At 3 months, 12 participants had PTSD. There was no relation between PTSD status and age (mean age=44.1, SD=15.5, for PTSD subjects versus mean=37.5, SD=16.1, for subjects without PTSD) (t=1.17, df=33, p=0.25), marital status (p=0.27, Fisher’s exact test), level of employment (p=0.11, Fisher’s exact test), or type of trauma (χ2=0.35, df=4, N=35, p=0.55). As expected, the Peritraumatic Dissociative Experiences Questionnaire scores of the 12 participants with PTSD (mean=3.1, SD=0.9) were higher than the scores of the 23 participants without PTSD (mean=2.3, SD=0.6) (t=3.2, df=33, p<0.01). Also as expected, Stanford Acute Stress Reaction Questionnaire scores of the participants with PTSD (mean=88.2, SD=30) were higher than those of participants without PTSD (mean=59.5, SD=27.6) (t=2.8, df=33, p<0.01).
We examined Pearson’s intercorrelation coefficients between peritraumatic dissociation and acute stress symptoms and PTSD symptoms and diagnosis. As shown in t1, peritraumatic dissociation and acute stress symptoms were related to PTSD symptoms and diagnosis. The overlapping confidence intervals around the correlations, particularly the subscales of the Stanford Acute Stress Reaction Questionnaire, suggest that no early predictor is significantly stronger than any other.
We next compared the predictive power of peritraumatic dissociation and total acute stress symptoms in explaining the occurrence of PTSD symptoms 3 months after the trauma. After ruling out collinearity between our two predictors (variance inflation factor=1.53, tolerance=0.65), we computed a hierarchical multiple linear regression (10). Peritraumatic dissociation, which occurs first and is of short duration, was entered first and accounted for adjusted R2=25.8% of the PTSD symptoms (F=12.80, df=1, 33, p=0.001). Entered in the second step, the acute stress symptoms accounted for an additional 7% of the variance (t=2.10, p=0.044), for a total of 32.8% (F=9.25, df=1, 32, p=0.001). Reversing the order of entry of the variables led to acute stress symptoms explaining 28.1% of the PTSD symptoms and the peritraumatic dissociation explaining an additional 4.6% of the variance (t=1.80, p=0.08).