Traumatic event vs. trauma
Not every hard event in life turns into a trauma.
A traumatic event is any situation that overwhelms us emotionally, such as an accident, a significant loss, an experience of violence or a natural disaster. It doesn't necessarily leave a lasting mark on the nervous system.
Trauma happens when the brain can't process that event. Francine Shapiro, who created EMDR, described it as information that gets "stuck" in the nervous system. The experience doesn't integrate with the rest, and the person keeps reliving the distress through intrusive memories, nightmares or physical symptoms, even when the danger has passed. It can get in the way of daily life.
The same event affects people differently. Some process it and move on. Others develop a trauma, depending on their personal history, their age, the support around them and whether it happened more than once.
EMDR helps "unlock" these stuck memories so the brain can process and store them adaptively. The person can then remember what happened without the same distress.

