A Second Look at Prior Trauma and the Posttraumatic Stress Disorder Effects of Subsequent Trauma

CONTEXT: Previous studies showed increased probability of a posttraumatic stress disorder (PTSD) effect of trauma in persons who had experienced prior trauma. The evidence comes chiefly from retrospective data on earlier events, obtained from trauma-exposed persons with and without PTSD. A generally overlooked major limitation is the failure to assess the PTSD response to the prior trauma. OBJECTIVE: To estimate the risk of PTSD after traumas experienced during follow-up periods in relation to respondents' prior traumatic events and PTSD. DESIGN: A cohort study of young adults interviewed initially in 1989, with repeated assessments during a 10-year follow-up. SETTING AND PARTICIPANTS: The sample was randomly selected from a large health maintenance organization in Southeast Michigan, representing the geographic area. MAIN OUTCOME MEASURES: The relative risk of PTSD precipitated by traumatic events occurring during follow-up periods in relation to prior exposure and PTSD that had occurred during preceding periods, estimated by general estimating equations (n = 990). RESULTS: The conditional risk of PTSD during the follow-up periods was significantly higher among trauma-exposed persons who had experienced prior PTSD, relative to those with no prior trauma (odds ratio, 3.01; 95% confidence interval, 1.52-5.97). After adjustment for sex, race, education, and preexisting major depression and anxiety disorders, the estimates were only marginally revised. In contrast, the conditional risk of PTSD during follow-up among trauma-exposed persons who had experienced prior traumatic events but not PTSD was not significantly elevated, relative to trauma-exposed persons with no prior trauma. The difference between the 2 estimates was significant (P = .005). CONCLUSIONS: Prior trauma increases the risk of PTSD after a subsequent trauma only among persons who developed PTSD in response to the prior trauma. The findings suggest that preexisting susceptibility to a pathological response to stressors may account for the PTSD response to the prior trauma and the subsequent trauma.