Trauma- and stressor-related disorders
Trauma- and stressor-related disorders occur following exposure to a traumatic or other stressful event. They differ according to the timing of exposure and age at manifestation. Post-traumatic stress disorder (PTSD) develops following exposure to actual or threatened death, serious injury, or sexual assault. Intrusions, distressing dreams, dissociative reactions (flashbacks), intense psychological distress, and physiological stress responses at exposure to internal of external cues that symbolize aspects of the traumatic event are typical for PTSD. Behaviourally, PTSD reflects a strategy of defence involving avoidance, attentive immobility, withdrawal, aggressive defence, appeasement, and tonic immobility, some of which are ancient vertebrate heritage. These defence mechanisms are preceded by heightened vigilance and risk assessment. Persistent stress responses often occur when important biosocial goals had been thwarted by the traumatic event. Species with long life-history patterns may be more vulnerable to developing PTSD than species with short life cycles.