Since a diagnosis of Post-Traumatic Stress Disorder (PTSD) describes long-term stress reactions after trauma, a new diagnosis of Acute Stress Disorder (ASD) has been formulated to describe the immediate reaction to trauma that may develop into PTSD.
This study used a sample of 63 mild traumatic brain injury (MTBI) and 72 non-TBI motor vehicle accident patients. The authors assessed and compared their symptom profiles upon admission for ASD, and 6 months later for PTSD. ASD was found in 14% of the MTBI patients, and in 13% of the non-TBI patients. PTSD eventually developed in 24% of the MTBI patients, and in 25% of the non-TBI patients.
In both the ASD and PTSD evaluations the authors found the non-TBI patients reported more feelings of fear and helplessness than the MTBI subjects. Non-TBI survivors had intrusive memories of the trauma during the acute phase (more often then MTBI patients), but the intrusive memories significantly decreased during the PTSD phase. The authors explain why the non-TBI patients were more affected by trauma:
"This finding may be explained by the impaired consciousness in the MTBI patients at the time of the trauma. It is plausible that these individuals interpreted the event as less frightening than their non-TBI counterparts because they were not fully aware of certain aspects of the events. Considering that most MTBI patients involved in acceleration-deceleration injuries lose consciousness at the point of impact, it is reasonable to argue that the immediate awareness of threat is reduced in these individuals."
The authors conclude that MTBI does not result in a different symptom profile for long term PTSD. Yet, the authors do acknowledge that MTBI PTSD is more complex since it involves a wider range of difficulties—such as cognitive deficits, fatigue, visual disturbances, and headaches. So although symptom inventories and percentage scores may be comparable, the course of PTSD differs greatly in MTBI patients.
Bryant R, Harvey A. The influence of traumatic brain injury on acute stress disorder and post-traumatic stress disorder following motor vehicle accidents. Brain Injury 1999;13: 15-22.