Young adults are known to be at elevated risk of self-injurious thoughts and behaviors (SITB), but little is known about the proximal predictors of suicide risk and non-suicidal self-injury (NSSI) urges and behaviors. Ecological momentary assessment (EMA) methods have been used to capture daily life processes related to SITB risk, but methodological questions remain with respect to the best practices to assess SITB. This study will enroll a sample of young adults ages 18-34 (N = 100) who report non-suicidal self-injurious thoughts (urges) or behaviors in the month prior to study participation. Participants will be asked to complete a battery of self-report questionnaires and interviews through a virtual visit, after which they will be invited to participate in a two-week (14-day) EMA protocol. For 7 days, participants will be prompted on a signal-contingent, pseudo-random basis, 6 times per day. For an additional 7 days, participants will be instructed to complete a survey on an event-contingent basis whenever they experience self-injurious thoughts or behaviors (SITB), as many times per day as applicable. The order of these protocols will be randomized across participants to control for time effects. Each survey will take approximately 3 minutes, and will assess SITB, negative and positive affect, interpersonal experiences, and a variety of risk factors for SITB (e.g., hopelessness, loneliness, emotional pain, access to means of self-injury).