Relating to a study from 2004:
A team of German scientists conducted experiments on a group of old German army veterans who took part in World War II. The research was conducted to see if traumatic and horrific dreams truly have a profound effect on a human being. The scientists realized that, after broad research, dreams have long-lasting effects on human beings and can persist up to 60 years since the dream first occurred. The German soldiers who were tested were very disturbed by dreams about their experiences in World War II. The scientists believed that dreams can keep coming back because the human being never really comes to terms with what the dream is about. The person never understands why the dream keeps happening over and over again and they also do not know how to stop the dreams from continuing.
Psychologists tend to make sense of these persistent dreams by believing that the brain is processing information of an event that does not yet make sense to the human being. Dr. Delia Cushway of ConventryUniversity made this claim and she interprets dreams as hints to cure stressful situations that need to be taken care of in order to achieve calmness and making sense of an event. Dreams recur because the event has not been solved yet. On a final note, Dr. Cushway verifies that every person dreams differently and that one traumatic dream can have a totally opposite situation that does not even relate to the stress experienced by the human being.