Emotion regulation mediates the effect of insomnia on non-suicidal self-injury in adolescents: The moderating role of mindfulness

Background Non-suicidal self-injury (NSSI) is common among adolescents, yet the role of insomnia in its development remains understudied. This study aims to investigate the association between insomnia and NSSI, focusing on the mediating role of emotion regulation and the moderating effect of mindfulness. Methods A cross-sectional survey was conducted among 4,259 students at a vocational and technical school in China. Participants were stratified into two groups based on the presence or absence of NSSI behaviors within the past year. Demographic data and standardized assessments were collected, including the Insomnia Severity Index (ISI), Difficulties in Emotion Regulation Scale (DERS), Mindful Attention Awareness Scale (MAAS), and the Adolescent Non-Suicidal Self-Injury Assessment Questionnaire (ANSAQ). Structural equation modeling (SEM) was used to test hypothesized relationships. Results Among the participants, 34.7% (n = 1,402) reported NSSI in the past year. Those with NSSI showed significantly higher insomnia severity, greater emotion dysregulation, and lower mindfulness (all p _s < 0.01). Insomnia was indirectly associated with NSSI through increased emotion regulation difficulties ( p  < 0.01). Mindfulness moderated this pathway, attenuating the impact of insomnia on both emotion dysregulation and subsequent NSSI (both p _s < 0.01). Conclusions Insomnia increases NSSI risk by impairing emotion regulation, while mindfulness mitigates this effect. These findings highlight key psychological mechanisms and support mindfulness-based approaches in NSSI prevention, particularly for adolescents with low trait mindfulness.