Post-traumatic amnesia is associated with increased arousal and reactivity symptoms following acquired brain injury

Post-traumatic amnesia is a common consequence of acquired brain injury and is characterized by impaired autobiographical memory for the traumatic event. For this reason, post-traumatic amnesia has traditionally been considered to reduce the risk of post-traumatic stress disorder, particularly symptoms based on explicit recollection of the trauma. However, post-traumatic stress symptoms may also emerge in the absence of conscious memory of the event.

To examine whether post-traumatic amnesia is associated with different patterns of post-traumatic stress symptoms following acquired brain injury.

Fifty-six patients with acquired brain injury were divided into two groups: patients with post-traumatic amnesia (n = 31) and patients without post-traumatic amnesia (n = 25). Post-traumatic stress symptoms were assessed using the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders - Clinician Version. Functional disability and self-awareness were also evaluated.

Post-traumatic stress disorder diagnoses were rare in both groups. However, patients with post-traumatic amnesia showed significantly higher arousal/reactivity symptoms than patients without post-traumatic amnesia, whereas no significant group differences emerged with regard to the dimension of intrusion, avoidance, negative alterations in cognition and mood, or general anxiety levels. Time since injury was positively associated with arousal symptoms in both groups. Functional disability predicted arousal only in patients without post-traumatic amnesia, while impaired self-awareness was negatively associated with arousal in the overall sample.

The present findings challenge the traditional "amnesia-protection" hypothesis and support a more nuanced understanding of post-traumatic stress symptoms following acquired brain injury. Trauma-related emotional responses may persist despite impaired autobiographical memory for the traumatic event, highlighting the need for multidimensional approaches to the assessment of post-traumatic stress symptoms in this population.