There was no clear recognition of the chronic, long-term post-traumatic stress reactions before the diagnosis of PTSD. The amygdala (1), hippocampus (2) and HPA axis (3) are imperative in the development and maintenance of PTSD. The hippocampus and amygdala are involved in the registration of dangerous events and the formation of memories about this.

Memories formed under emotionally arousing situations behave differently from those that are not. Memory formation can be altered by the blocking effects of adrenalin. This means that the degree of arousal during or directly after a traumatic event has fundamental importance for the development of intrusive and hyperarousal symptoms.

Acute stress disorder (ASD) is a good predictor of PTSD but does not necessarily lead to the development of PTSD. The prevalence of PTSD is higher for women and minority groups, potentially due to their high exposure to traumatic events (e.g. sexual assault). The lifetime prevalence of exposure to a traumatic event is more than 50%.

There are several predictors of PTSD:

1. History of prior trauma
   People who have experienced prior trauma experience higher levels of PTSD. Childhood trauma does not lead to a higher risk than adult trauma. The strongest effects were found for non-combat interpersonal violence (e.g. assault; torture).
2. Psychological problems prior to target stressor
   People who had more problems in psychological adjustment prior to the trauma experience higher levels of PTSD. This includes mental health treatment (1), pre-trauma emotional problems (2), pre-trauma anxiety of affective disorders (3), and anti-social personality disorder (4). This relationship was stronger when less time had elapsed between the trauma and the assessment of PTSD.
3. Psychopathology in family of origin
   People who had a family history of psychopathology experience higher levels of PTSD symptoms. This effect is stronger if the trauma involves non-combat interpersonal violence.
4. Perceived life threat
   People who believed their life was in danger during the traumatic event experience higher levels of PTSD. This relationship was stronger when more time had elapsed between the trauma and the assessment of PTSD and when the trauma involved non-combat interpersonal violence.
5. Perceived social support following trauma
   People who perceived lower levels of social support following trauma experience higher levels of PTSD. This relationship was stronger when more time elapsed between the trauma and the assessment of PTSD and for people who experienced a combat-related trauma (e.g. military).
6. Peritraumatic emotional responses
   People who have intensely negative responses (e.g. fear, horror, helplessness, shame, guilt) during or immediately after the trauma experience higher levels of PTSD symptoms.
7. Peritraumatic dissociation
   People who had more dissociative experiences during or immediately after the trauma experience higher levels of PTSD symptoms. This relationship was strongest when 6 months to 3 years had elapsed since the trauma.

Peritraumatic dissociation is most strongly related to individuals seeking mental health services. This is only measurable after the trauma. It may occur because the trauma is so severe that it becomes intolerable. However, there is no objective measurement of the severity of a traumatic event.

Social support may function as a secondary intervention. The effects are cumulative over time. People are more likely to receive social support for psychological processing of the trauma (e.g. meaning of the event) than other needs after the trauma (e.g. financial support).

The predictors of PTSD may indicate a lack of psychological resilience and this makes people vulnerable to the development of PTSD after a trauma. One of the key aspects of dealing with the aftermath of a trauma and PTSD is coming to terms with loss. This could explain the comorbidity with depression.