From Vaughan Bell’s “Ghost Stories: Visits from the Deceased” (Scientific American: 2 December 2008):
The dead stay with us, that much is clear. They remain in our hearts and minds, of course, but for many people they also linger in our senses—as sights, sounds, smells, touches or presences. Grief hallucinations are a normal reaction to bereavement but are rarely discussed, because people fear they might be considered insane or mentally destabilised by their loss. As a society we tend to associate hallucinations with things like drugs and mental illness, but we now know that hallucinations are common in sober healthy people and that they are more likely during times of stress.
Mourning seems to be a time when hallucinations are particularly common, to the point where feeling the presence of the deceased is the norm rather than the exception. One study, by the researcher Agneta Grimby at the University of Goteborg, found that over 80 percent of elderly people experience hallucinations associated with their dead partner one month after bereavement, as if their perception had yet to catch up with the knowledge of their beloved’s passing. As a marker of how vivid such visions can seem, almost a third of the people reported that they spoke in response to their experiences. In other words, these weren’t just peripheral illusions: they could evoke the very essence of the deceased.
Occasionally, these hallucinations are heart-rending. A 2002 case report by German researchers described how a middle aged woman, grieving her daughter’s death from a heroin overdose, regularly saw the young girl and sometimes heard her say “Mamma, Mamma!” and “It’s so cold.” Thankfully, these distressing experiences tend to be rare, and most people who experience hallucinations during bereavement find them comforting, as if they were re-connecting with something of the positive from the person’s life. Perhaps this reconnecting is reflected in the fact that the intensity of grief has been found to predict the number of pleasant hallucinations, as has the happiness of the marriage to the person who passed away.
There are hints that the type of grief hallucinations might also differ across cultures. Anthropologists have told us a great deal about how the ceremonies, beliefs and the social rituals of death differ greatly across the world, but we have few clues about how these different approaches affect how people experience the dead after they have gone.