Scientists know that the intense stress of grieving can affect the body in various ways, but much remains a mystery. Mary-Frances O'Connor, a psychologist who researches grief at the University of Arizona, studies both the psychology of grief and its biological changes in the laboratory and is one of the few researchers who straddles both fields. "Humans are predisposed to form loving bonds, and as soon as you do, your body is loaded and cocked for what happens when that person is gone.