Awake/sleep cortisol levels and the development of posttraumatic stress disorder in injury patients with peritraumatic dissociation.

Differences in the time of day that cortisol is sampled and failure to consider the impact of peritraumatic dissociation have been hypothesized as factors possibly contributing to the inconsistent findings in research examining associations between cortisol levels soon after trauma exposure and the subsequent development of posttraumatic stress disorder (PTSD). The present study examined associations between urinary cortisol levels during wake and sleep times soon after a serious injury and the subsequent development of PTSD in adult patients reporting low or high peritraumatic dissociative (PD) symptoms. Thirty-nine injury patients (20 with high and 19 with low PD symptoms) provided a 15-hour (6 PM to 9 AM) urine sample at 3-weeks post-injury and completed the Clinician Administered PTSD Scale at a 7-week follow-up. Participants collected their urine during wake and sleep times separately. Results showed that in the total sample and in the high PD group, wake, but not sleep, cortisol levels were lower in patients who developed PTSD compared to those who did not. A multiple linear regression analysis revealed a significant main effect of PD and a non-significant interaction between wake cortisol and PD in predicting PTSD symptom severity. In addition, results showed that PD was a better predictor of PTSD symptom severity than wake cortisol levels. These results were consistent with prior research indicating lower afternoon/evening cortisol levels in PTSD and strong associations between PD and PTSD, but did not support the existence of subgroups of PTSD patients (dissociators versus non-dissociators) who may differ in basal cortisol levels.