Project Summary Suicide is a leading cause of death worldwide and the second leading cause of death for adolescents in the US. Despite advances in understanding of suicidal thoughts and behaviors and their treatment, the suicide rate has not decreased. One possible factor limiting progress in this area has been a lack of focus on understanding (and targeting) developmental mechanisms that may give rise to suicidal thoughts and behaviors. Interoception, the perception of internal bodily states, holds promise as a novel factor that may increase risk for suicide. Suicidal thoughts and behaviors center around inflicting harm to the body, yet surprisingly little work has tested whether and how disrupted interoceptive processes may contribute to risk for suicide. Given the centrality of the body in suicidal thoughts and behaviors and the unique interoceptive learning and processing that may occur during adolescence, altered interoceptive processing represents a novel risk factor that may advance understanding of suicidal thoughts and behaviors among adolescents. This proposal tests the associations between interoceptive processes and the occurrence of suicidal thoughts and behaviors. Eighty adolescents with and without suicidal thoughts and behaviors will undergo assessments of suicidal thoughts and behaviors, psychophysiological measurement of interoceptive processes, exposure to childhood trauma, and ecological momentary assessments of suicidal thoughts and behaviors and appraisals of body sensations. Aim 1 of this proposal is to test the association between perceptual interoceptive processes (i.e., interoceptive accuracy, sensitivity, and attention) and suicidal thoughts and behaviors. Aim 2 of this proposal is to test the association between appraisals and descriptions of body sensations and suicidal thoughts and behaviors. Aim 3 of this proposal is to test whether interoceptive processes are a potential mediator of the associations between childhood trauma and suicidal thoughts and behaviors. The proposed study’s greatest potential impacts are to use innovative strategies to study a novel potential risk factor for suicidal thoughts and behaviors, identify putative pathways that have clear translational value, and to potentially identify novel targets for intervention to treat suicidal thoughts and behaviors in adolescents.