The interpersonal-psychological theory of suicidal behavior (Joiner, 2005) proposes that an individual will not die by suicide unless s/he has both the desire to die by suicide and the ability to do so. What is the desire for suicide, and what are its constituent parts? What is the ability to die by suicide and in whom and how does it develop?
In answer to the first question of who desires suicide, the theory asserts that when people hold two specific psychological states in their minds simultaneously, and when they do so for long enough, they develop the desire for death. The two psychological states are perceived burdensomeness and a sense of low belongingness or social alienation. In answer to the second question regarding capability for suicide, self-preservation is a powerful enough instinct that few can overcome it by force of will. The few who can have developed a fearlessness of pain, injury, and death, which, according to the theory, they acquire through a process of repeatedly experiencing painful and otherwise provocative events. These experiences often include previous self-injury, but can also include other experiences, such as repeated accidental injuries; numerous physical fights; and occupations like physician and front-line soldier in which exposure to pain and injury, either directly or vicariously, is common.