Abstract
OBJECTIVES: Non-suicidal self-injury (NSSI) is highly prevalent among adolescents and young adults with mood disorders. This study aims examine the occurrence and motivation of NSSI behavior in real-life contexts, as well as the dynamic characteristics of associated emotional changes. METHODS: An observational study was conducted among 135 adolescents and young adults with a history of NSSI urges and/or behaviors. Participants completed a 14-day ecological momentary assessment (EMA), with 3 random assessments per day capturing NSSI behavior, environmental factors, and mood states through a WeChat-based EMA mini-program, yielding a total of 3 976 assessments. According to whether NSSI behavior occurred during the EMA monitoring period, the participants were divided into the NSSI behavior (NSSI+) group and the non-NSSI behavior (NSSI-) group. Linear mixed-effects models were used to analyze trajectories of emotional change. RESULTS: A total of 31.9% of participants engaged in at least 1 episode of NSSI during the study period. Among NSSI behaviors, cutting was the most common (56.8%), followed by biting (15.2%). Regarding settings, most (68.6%) behaviors occurred at home, primarily during rest or inactivity (38.1%), and 44.9% of behaviors occurred when alone. Approximately 74.6% of behaviors followed non-interpersonal life events. The primary motivation was self-induced negative reinforcement. The NSSI group had a significantly younger age of first self-injury than the non-NSSI group (14.0 years vs 16.0 years, P<0.001). Linear mixed-effects analyses revealed that prior to NSSI episodes, negative affect increased significantly (P<0.05), while positive affect decreased significantly (P<0.05). Following NSSI, negative affect gradually declined, and positive affect progressively rebounded. The overall emotional trajectory resembled a quadratic curve. CONCLUSIONS: NSSI behavior is closely associated with fluctuations in negative affect, and the accumulation of negative emotions may serve as a critical precursor to NSSI. Emotion regulation is the primary motivation for engaging in NSSI, suggesting that interventions targeting emotional processes may help reduce the occurrence of NSSI.