Predicting Non-Suicidal Self-Injury in Young Adults with and without Borderline Personality Disorder: a Multilevel Approach Combining Ecological Momentary Assessment and Self-Report Measures.

Non-suicidal self-injury (NSSI) is an increasingly prevalent phenomenon associated with many detrimental outcomes, ranging from poor academic performance to suicide attempts. Research on self-harming behaviors has identified emotion dysregulation, negative affect, and borderline pathology as strong risk factors of NSSI, whereas the potential protective effects of metacognitive skills such as decentering have not yet been explored. The current study combined ecological momentary assessment (EMA) and self-report measures to explore potential risk and protective factors of NSSI in a clinical group of Borderline Personality Disorder (BPD) patients with NSSI (N = 22), a subclinical group of college students with NSSI (N = 19), and a non-clinical healthy control group (N = 23). Participants completed self-report measures of borderline pathology, emotion dysregulation, decentering ability, and negative emotional symptoms, and they used the Sinjur App (EMA instrument) at least three times a day for 15 days to capture negative affect and NSSI in daily life. A multilevel mixed-effect regression analysis with both self-report and EMA measures was conducted to identify predictors of NSSI. The multilevel analysis showed that only momentary frustration directly predicted NSSI. Momentary guilt and anger only predicted NSSI when interacting with more stable traits of borderline pathology and negative emotional symptoms. Most importantly, greater decentering capacity protected against self-injury and attenuated the association between momentary sadness and NSSI. Findings contribute novel knowledge about NSSI, documenting the protective effects of decentering and highlighting the benefit of interventions that target metacognitive emotion regulation skills.