Grief (novel)
During the course of the novel, the ideas of the stages of grief are introduced. The stages are denial, anger, depression, and acceptance. The narrator, as well as other characters in the story, slowly passes through these stages in trying to deal with death.
Prolonged grief disorder
Grief is a normal response to bereavement. Researchers have found that 10–20% of people experience a prolonged response to bereavement that impacts functioning and has adverse long-term effects on health.