BACKGROUND Most individuals who, shortly after trauma, express symptoms of post-traumatic stress disorder (PTSD) recover within one year of their traumatic experiences. In contrast, those who remain ill for one year rarely recover completely. The early identification of the latter is, therefore, very important.

AIMS To prospectively evaluate predictors of PTSD at four months and one year.

METHOD We followed 236 trauma survivors recruited from admissions to a general hospital's emergency room for four months, at which point 41 (17.4%) met diagnostic criteria for PTSD. Twenty-three of these individuals, and 39 individuals without PTSD at four months, were assessed again at one year.

RESULTS Depressive symptoms were the best predictors of PTSD at both time points. Intrusive symptoms and peri-traumatic dissociation were better at predicting four-month PTSD than one-year PTSD.

CONCLUSIONS The occurrence of depression during the months that follow a traumatic event is an important mediator of chronicity in PTSD.