When children and adolescents experience a situation as threatening and they respond in intense fear or helplessness, or sometimes in disorganization or in agitation, their brain is activated in a high level of arousal.  When this happens, it is extremely difficult to take in information or to think, as part of the brain (frontal lobe) is shut down, and the brain shifts to the right brain processing which is more emotional.

This makes it more difficult for the child to calm down and put the situation behind them.  The age of the child, and the context, severity and frequency of the situation, will affect how the brain, and therefore body, is affected biologically.  The original threatening situation, and any subsequent threatening situations, or sometimes reminders of the situation, can trigger the aroused emotional response. 

Treatment is to help the child learn how to self regular their emotions.  The child and family will be able to work with the therapist on identifying the onset and source of the child's symptoms, and to develop a plan to help the child to better regulate and cope with their emotions.