We assumed that time would heel wounds. We'll two years later and our son seems to be getting worse, he was 9 at the time of the accident. I think he is struggling with how to deal with his emotions and his imagination. It is like he believes everything that could go wrong will. I am hoping therapy will help. Be there for him. Take time to listen to his emotions and allow him to feel them.
A priesthood blessing might help, at a minimum it could be a reminder of the eternal.