Nonsuicidal self-injury (NSSI) is the intentional destruction of one’s body tissue without suicidal intent and for purposes not socially sanctioned. While NSSI has been understudied among Veterans, the lifetime prevalence rate of NSSI in Veterans (16%) is actually three times higher than the general population. NSSI is associated with risk for violence, psychiatric distress, and marked impairment in psychosocial functioning. Although NSSI is distinct from suicidal behaviors in several important ways, NSSI is one of the strongest predictors of a future suicide attempt identified to date. However, current interventions show limited efficacy for NSSI. There is a critical need to identify effective treatments for NSSI to improve functioning and prevent Veteran suicide. The proposed research aims to adapt and enhance a promising new treatment, the Treatment for Self-Injurious Behaviors (T-SIB), to reduce NSSI in Veterans. T-SIB is a nine-session individualized treatment that incorporates evidence-based approaches to replace NSSI with behaviors that improve psychosocial functioning. A core component of T-SIB is functional assessment that tracks antecedents and consequences of NSSI behaviors to identify underlying functions of an individual’s NSSI. In Aim 1, T-SIB will be adapted for use with Veterans and enhanced to incorporate functional assessments administered via ecological momentary assessment (EMA). EMA reduces retrospective recall bias and can capture NSSI behaviors in-vivo. A successive cohort design including two cohorts of Veterans (n = 5 each) will be used to refine the T-SIB protocol. Qualitative and quantitative data will be reviewed after each cohort to make successive modifications. In Aim 2, the feasibility and acceptability of T-SIB will be evaluated with a pilot randomized controlled trial (RCT). Veterans with NSSI (N = 40) will be randomized to T-SIB enhanced with EMA or treatment as usual (i.e., safety planning and referral to mental health services). Primary outcomes will include measures of feasibility and acceptability. Additional measures of NSSI and psychosocial functioning will be administered at baseline, posttreatment, and a three-month follow-up. In Exploratory Aim 3, multilevel modeling will be applied to EMA functional assessments to examine intra- and inter-individual changes in antecedents, consequences, and NSSI functions over a nine-week period. Study aims will support future investigator-initiated research (IIR) applications to conduct a fully powered RCT to test the efficacy of T-SIB for Veterans. The candidate is a postdoctoral fellow in the Mid-Atlantic Mental Illness Research, Education and Clinical Center (MIRECC) at the Durham VA. The training aims associated with this proposal include: 1) gain expertise in treatment development and clinical trial methodology; 2) acquire skills in advanced modeling of longitudinal data; and 3) engage in professional development to prepare for a successful career as a VA clinica...