Engel wrote about sudden and rapid death during psychological stress in 1971 and itemized 8 causation categories: on the impact of the collapse or death of a close person; [2 during acute grief; on threat of loss of a close person; [4 during mourning or on an anniversary; on loss of status or self-esteem; [6 personal danger or threat of injury; after the danger is over; [8 reunion, triumph, or happy ending. He proposed these events provoke neurovegetative responses, involving both the flight-fight and conservation-withdrawal systems, conducive to lethal cardiac events, particularly in individuals with preexisting cardiovascular disease.