This is post traumatic stress disorder. The young persons' perceptions of the event is the most important feature and their life does not actually have to be in danger.
It can be seen after road traffic accidents, witnessing domestic violence, after experiencing child sexual abuse and many other difficult situations.
The young person may experience vivid dreams and nightmares that may wake them from their sleep. They may stay awake in order to avoid sleep.
The young person may not understand what is happening to them so may not immediately share these difficult experiences.
They become hyper vigilant and will startle easily to loud noises, for example a slammed door or a noisy car driving past them in the street.
They may start to avoid triggers that reminder them of the difficult event, for example, not wanting to travel in a car.
Young people and adults will have a better outcome if this is recognised and treated sooner. Chronic PTSD can cause hi levels of morbidity and difficulties.
There are a a few different interventions that are effective.
Usually a young person would start with CBT talking therapy that has a trauma informed focus.
An alternative is eye-movement desensitisation re-processing therapy.
Medication can also be very helpful.
PTSD can be treated and the symptoms can be reduced, but early action leads to better outcomes.