A traumatic event involves an experience or recurring experience that completely overwhelms an individual's ability to cope.
Due to the controversial and highly emotional nature of trauma, the selection of those traumas for the piece are delicately selected to either develop characters or the primary plot. The selection is often made because the creator wishes to explore the depths of a particular trauma. What are the prolonged effects of child abuse on the child? What reactions does someone have after years of verbal abuse? How does an individual perceive the world after the loss of a loved one? How does a rape victim cope? These particular traumas are extremely powerful but it is also important to note that these can have an adverse response from the audience. Not everyone will want to explore these 'dark' emotions.
Attempting to explore trauma is highly contingent on understanding the psychological effects of the trauma on an individual. Often after a traumatic experience a person may re-experience the trauma mentally and physically. They may turn to drugs or alcohol to escape as psychological triggers cause a re-experience of the event. The individual may suffer feelings of intense anger, resentment and guilt. Upsetting memories such as images, thoughts or flashbacks may haunt the person. Nightmares and insomnia may occur as their repressed fears keep the person on edge. As these stressors continue it can lead to emotional exhaustion and ultimately emotional detachment.
In a narrative piece that utilizes trauma as both backstory for individuals in the piece and as a core element of the primary plot, it is paramount to understand what that trauma actually does to the individuals that experience it. Just as imperative is understanding how an audience will perceive that trauma and if they are willing to confront those 'dark' emotions.