The stress-diathesis theory of suicide suggests a predisposition or diathesis interacts with stressful life experiences and acute psychiatric illness to cause suicidal behavior. The theory explains why only a small minority of individuals are at risk of taking their own lives after exposure to such stressors. The authors of a new article discuss the causes of the diathesis, or predisposition, to suicidal behavior, which may include genetic effects and the long-term impact on the brain and behavior of early life adversity (eg, physical and sexual abuse).