Background: The interpersonal theory of suicide posits that perceived burdensomeness, thwarted belongingness, and acquired capability together interact to increase risk for lethal self-injury. Despite the prominence of this theoretical model, few studies have directly tested the three-way interaction central to the theory, with mixed findings reported in studies to date. The objective of this study was to test the theorized three-way interaction in relation to suicidal behaviors in a large sample of college students.

Methods: Undergraduate students were recruited from two universities (N = 1,686; ages 18-29; 64.5% female). Participants completed measures of perceived burdensomeness and thwarted belongingness (Interpersonal Needs Questionnaire-25), fearlessness about death (Acquired Capability for Suicide Scale-Fearlessness About Death), and suicidal behaviors (Suicidal Behaviors Questionnaire-Revised).

Results: Multiple linear regression was used to test the three-way interaction among burdensomeness, belongingness, and fearlessness about death on suicidal behaviors. Controlling for sex and depressive symptoms, results indicated the presence of a significant three-way interaction. The interaction was probed by dichotomizing burdensomeness at high and low values. There was a significant two-way interaction at high burdensomeness such that low belongingness was only related to suicidal behavior at high levels of fearlessness about death.

Limitations: The study is cross-sectional and uses a composite measure of suicidal behaviors.

Conclusions: This study adds to a small but growing body of research testing the three-way interaction among perceived burdensomeness, thwarted belongingness, and capability for suicide in relation to suicidal behaviors. Longitudinal studies using measures that distinguish between suicidal ideation and suicide attempt within the ideation-to-action framework are needed.