Posttraumatic Stress Disorder or PTSD can have an effect on children. PTSD is an anxiety disorder. As with anxiety disorders, children can often be misdiagnosed as having ADD/ADHD. PTSD can develop after a terrifying ordeal that involves harm or the perception of harm. The key word here is "terrifying." What one person considers terrifying may not be terrifying to another person.
Generally, when people develop PTSD, there are three main symptoms. These symptoms of PTSD include: re-experiencing the event (e.g., bad dreams, frightening thoughts, etc.), avoidance of the experience (e.g., staying away from places, events, or objects that are reminders, emotionally, numb, etc.), and hyperarousal (being easily startled, having difficulty sleeping, etc.) Children who have developed PTSD can also regress and start bed wetting, forgetting or being unable to talk, or unusually clingy with the parents.
I generally use EMDR (one of the most effective ways of treating PTSD), hypnosis, rhythmic movement therapy, and attachment-focused play therapy in treating PTSD. I am one of the handful of counselors in the St Louis area who are consultants (this status requires about three years of additional training and supervision in EMDR) of EMDR.