Post-traumatic stress disorder (PTSD) is a type of trauma and stressor related disorder that develop in some people that directly experience or witness a shocking, scary or dangerous event that exposed them to actual or threatened death, serious injury or sexual violence.

In certain cases, it is possible to develop PTSD from learning that a traumatic event occurred to a close family member or friend, or from repeated exposure to aversive details of a traumatic event. Individuals with PTSD may have recurrent, involuntary and intrusive flashbacks of the event, feel like they are re-living the traumatic event, have nightmares related to the trauma experienced, and experience intense physiological and psychological distress at exposure to cues that symbolise the event.

Due to this they may actively avoid anything related to the traumatic event, develop dissociative amnesia, which is the inability to remember certain parts of the event, feel extreme shame, anger and guilt, and may display irritability, angry outburst, and hypervigilance after the event. These symptoms present themselves for a period of one month or more, and often lead to significant distress and impairment in social, occupational or other areas of functioning.