Nonsuicidal self-injury (NSSI) and borderline personality disorder (BPD) are serious mental health problems that may have common developmental pathways. Adverse childhood environments coupled with trait impulsivity and emotion dysregulation purportedly increase the risk of NSSI and BPD. The primary aim of this study was to examine the association of these risk factors with NSSI and BPD over a 1-year period among young adults (N = 229; aged 18-35; 75.5% female). Participants completed measures of relevant variables at baseline and every 3 months over 12 months. Hypotheses were that emotion regulation difficulties would mediate the association of childhood maltreatment with NSSI and BPD and that impulsivity would moderate the association of childhood maltreatment with ERD. Findings from multilevel modelling analyses indicated that emotion regulation difficulties mediated the association of childhood maltreatment with both NSSI and BPD. Contrary to hypotheses, impulsivity did not moderate the association of childhood maltreatment with emotion regulation difficulties. These findings highlight the importance of emotion regulation difficulties in NSSI and BPD among young adults.

Keywords: borderline personality disorder; childhood maltreatment; emotion regulation; nonsuicidal self‐injury; trait impulsivity.

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