Importance: Delayed-onset posttraumatic stress disorder (PTSD) accounts for approximately 25% of PTSD cases. Current models do not adequately explain the delayed increases in PTSD symptoms after trauma exposure.
Objective: To test the roles of initial psychiatric reactions, mild traumatic brain injury (MTBI), and ongoing stressors on delayed-onset PTSD.
Design, Setting, and Participants: In this prospective cohort study, patients were selected from recent admissions to 4 major trauma hospitals across Australia. A total of 1084 traumatically injured patients were assessed during hospital admission from April 1, 2004, through February 28, 2006, and 785 (72.4%) were followed up at 3, 12, and 24 months after injury.
Main Outcome and Measure: Severity of PTSD was determined at each assessment with the Clinician-Administered PTSD Scale.
Results: Of those who met PTSD criteria at 24 months, 44.1% reported no PTSD at 3 months and 55.9% had subsyndromal or full PTSD. In those who displayed subsyndromal or full PTSD at 3 months, PTSD severity at 24 months was predicted by prior psychiatric disorder, initial PTSD symptom severity, and type of injury. In those who displayed no PTSD at 3 months, PTSD severity at 24 months was predicted by initial PTSD symptom severity, MTBI, length of hospitalization, and the number of stressful events experienced between 3 and 24 months.
Conclusions and Relevance: These data highlight the complex trajectories of PTSD symptoms over time. This study also points to the roles of ongoing stress and MTBI in delayed cases of PTSD and suggests the potential of ongoing stress to compound initial stress reactions and lead to a delayed increase in PTSD symptom severity. This study also provides initial evidence that MTBI increases the risk of delayed PTSD symptoms, particularly in those with no acute symptoms.