background  Delayed posttraumatic stress disorder (PTSD) is a poorly understood phenomenon with important implications for recognition, prevention and treatment.                                                  aims To obtain insight into the relation between trauma, peritrauma factors and clinical, psychological and neurobiological aspects of delayed PTSD.
method  Literature search using Medline, PsycINFO and Embase over the period 1990-2001, using as key words posttraumatic stress disorder, delayed, prospective, risk factors, repression, dissociation, dissociative, amnesia and neurobiology.
results  Delayed PTSD occurrred on average in 5,8% of trauma victims who were followed up prospectively. Risk factors include combat trauma, stressful events after the trauma and previous emotional problems. Repression, dissociative amnesia, cue- and context-dependent memory, timedependent sensitisation and kindling have all been linked to delayed ptsd.
conclusion  Delayed PTSD is related to avoidance, the absence of cue- and context-dependent recall associated with amnesia, and to neurobiological stress-sensitisation. Clinical implications include informing traumatised patients, the recognition of the adaptive value of amnesia in situations of perceived threat and the clinical recognition of delayed PTSD.