Delayed-onset PTSD: a prospective study of injury survivors

Recent studies have indicated that delayed-onset posttraumatic stress disorder (PTSD) (i.e., the development of PTSD more than 6 months posttrauma) is generally characterised by subsyndromal diagnoses within the first 6 months. This study sought to examine the relationship between sub-clinical levels of PTSD symptoms at 3 months posttrauma and delayed onset PTSD at 12 months in a large sample of traumatic injury survivors.

Three hundred and one consecutively admitted injury survivors were assessed at 3 and 12 months posttrauma. PTSD was diagnosed according to DSM-IV criteria, while partial and subsyndromal diagnoses were based on recent definitions developed by Mylle and Maes [Mylle, J., Maes, M., 2004. Partial posttraumatic stress disorder revisited. J. Affect. Disord. 78, 37-48].

Eight percent of participants was diagnosed with 3-month PTSD while 10% was diagnosed with 12-month PTSD. Nearly half (47%) of 12-month PTSD cases were of delayed onset. The majority of those with delayed-onset were diagnosed with partial or subsyndromal PTSD at 3 months. Ten percent of delayed onset cases did not meet partial or subsyndromal criteria.

As symptoms were not assessed at 6 months (the DSM cut-off for delayed PTSD), it could not be conclusively determined that delayed-onset cases had not developed PTSD between 3 and 6 months posttrauma.

A considerable proportion of 12-month PTSD diagnoses was delayed in onset. While most demonstrated 3-month morbidity in the form of partial and subsyndromal diagnoses, a minority did not. Thus, clinicians should consider subthreshold diagnoses as potential risk factors for delayed-onset PTSD. Future research is required to identify factors that may predict delayed-onset PTSD in trauma survivors without evidence of prior PTSD pathology.