A variety of mechanisms have been proposed which link suicide risk factors and behavior, including psychache, thwarted belongingness, and escape from self, among others. While strong evidence for the predictive power of these variables exists, it remains unclear why these proximal mechanisms are systematically linked to seemingly maladaptive outcomes (i.e., suicidal behavior) across individuals. Building on de Cantazaro (1991)’s inclusive fitness model of suicide, we review proximal mechanisms of suicide — including thwarted belongingness, perceived burdensomeness, hopelessness, psychache, body image, and others — and suggest functionally specific outcomes which these may be tracking. In the process, we discuss the fitness consequences of risk factors associated with each mechanism (e.g. incarceration, job loss, rejection, etc.) and draw connections to otherwise puzzling suicide predictors (e.g. food insecurity). In so doing, we establish a preliminary framework connecting ultimate and proximate explanations on which future models of suicidality may build. We conclude by discussing possible implications for suicide prevention and emphasizing the need for a unified theoretical account of suicide which considers psychological, functional, and biological levels of analysis.

Significance. The work adds to our knowledge of the topic by bridging the theoretical divide between traditional models of suicide (e.g. the interpersonal Theory of Suicide, Suicide as Escape from Self, etc.), which focus on subjective experiences, and functional models of suicide, which focus on evolutionary explanations of suicide. By reviewing various proximate mechanisms and connecting these to specific, functional explanations suicide interventions may be created which target both the proximate cognitive processes underlying suicide as well as the environmental circumstances likely to produce suicidal behavior.