Trauma is a response to an overwhelming situation where adequate support was not provided to process what happened.
Individual trauma results from an event, series of events, or set of circumstances that is experienced by an individual as physically or emotionally harmful or life threatening and that has lasting adverse effects on the individual’s functioning and mental, physical, social, emotional, or spiritual well-being.
And as defined by the UK Trauma Council:
Trauma refers to the way that some distressing events are so extreme or intense that they overwhelm a person’s ability to cope, resulting in lasting negative impact.
After experiencing or witnessing an extremely distressing event, many children and young people will initially experience high levels of distress and find it difficult to get on with their normal life. Most of those will spontaneously recover in the weeks and months that follow, while others will develop lasting difficulties. A minority of children and young people initially may experience very little reaction even to extreme events. But over a longer period of time, some of those seemingly unaffected children and young people may develop a range of difficulties.
Rather than being stored as normal memories, trauma may be stored as raw emotions, sensations, and beliefs. These attributes often do not respond to present-day logic and must be processed to fully change them, though some change can be made without processing.
How Trauma Differs from Normal Memory
It is important to note that traumatic memories are very different from processed narratives of trauma. While narrative memories are verbal, time-condensed, social and reconstructive in nature, traumatic memories are often experienced as if the once overwhelming event were happening here and now. These hallucinatory, solitary, and involuntary experiences consist of visual images, sensations, and motor actions, which engross the entire perceptual field. Apart from the individualis experience of the event, they may include his or her fantasy and misperceptions at the time, and exclude parts of the experience.
For example, the traumatic memory of Charcotis patient LeLog included the idea that he had been run over by a wagon. In fact, before losing consciousness, he had seen the wheels approaching him, which impressed upon him the idea of being run over, though he was actually never hit. Also, elements of other (traumatic) experiences may become associated with the traumatic memory, and thus confound it.
Ellert Nijenhuis, Onno van der Hart, & Kathy Steele, 2004, Trauma-related Structural Dissociation of the Personality
See also: Flashbacks, The World is Traumatic, Processing Trauma, You Are Not Inherently Bad