A Study of the Protective Function of Acute Morphine Administration on Subsequent Posttraumatic Stress Disorder

Background: To index the extent to which acute administration of morphine is protective against development of posttraumatic stress disorder (PTSD). Methods: Consecutive patients admitted to hospital after traumatic injury (n = 155) were assessed for current psychiatric disorder, pain, and morphine dose in the initial week after injury and were reassessed for PTSD and other psychiatric disorders 3 months later (n = 120). Results: Seventeen patients (14%) met criteria for PTSD at 3 months. Patients who met criteria for PTSD received significantly less morphine than those who did not develop PTSD; there was no difference in morphine levels in those who did and did not develop major depressive episode or another anxiety disorder. Hierarchical regression analysis indicated that PTSD severity at 3 months was significantly predicted by acute pain, mild traumatic brain injury, and elevated morphine dose in the initial 48 hours after trauma, after controlling for injury severity, gender, age, and type of injury. Conclusions: Acute administration of morphine may limit fear conditioning in the aftermath of traumatic injury and may serve as a secondary prevention strategy to reduce PTSD development.