Thomas Joiner is a prominent psychologist known for his research on suicide, particularly his interpersonal theory of suicide. This theory emphasizes that suicidal behavior is influenced by the interplay of perceived burdensomeness, thwarted belongingness, and the acquired capability for suicide. Joiner's work helps identify risk factors and warning signs associated with suicidal ideation and attempts, providing insights into how these elements can contribute to an individual's decision to engage in self-harm.