Developmental stages of understanding of Death:
Preschool children mostly see death as temporary, reversible, and impersonal. In the stories they hear and the movies they watch, characters will suddenly rise up and live again even after being “destroyed” or “killed”. It is not surprising that they do not understand the finality or seriousness of death. It is age appropriate for them to think this way.
Between ages of 5 years and 9 years, most children are beginning to see that all living things eventually die, and that death is final. They tend to not relate it to themselves---they consider that everything else dies but not them. They may associate certain images with death, such as a skeleton. They may have nightmares that include these images. They may also begin to worry about mommy, daddy and other loved ones might die and this can cause nightmares. This can cause the child to feel nervous about being away from the parents now that the possibility of death is real.
From 9 years through adolescence, children begin to fully understand that death is irreversible and that they too will die someday. Nightmares now can focus on the child worrying that he/she will die soon and each time the child is ill, they may be very upset because they worry, they may die.