The Effectiveness of Acceptance and Commitment Therapy on Non-Suicidal Self-Injury and Executive Functions in Patients with Borderline Personality Disorder

Abstract

Borderline personality disorder (BPD) is a complex clinical condition characterized by affective instability, impulsivity, interpersonal dysregulation, identity disturbance, and recurrent self-harming behaviors. Non-suicidal self-injury (NSSI) is particularly important in BPD because it is often used as a short-term strategy for regulating painful emotions, yet it is associated with considerable clinical risk and functional impairment. Executive functions, including inhibition, planning, self-organization, emotional self-regulation, and self-motivation, are also frequently impaired in this population. Acceptance and Commitment Therapy (ACT) may be clinically useful because it targets experiential avoidance and promotes psychological flexibility, values-based action, and acceptance of difficult internal experiences. This quasi-experimental study used a pretest-posttest-follow-up design with a control group. The statistical population included patients diagnosed with BPD who attended psychological and psychiatric treatment centers in Shahrood, Iran, in 2022. Forty participants were selected by convenience sampling and were then randomly assigned to an ACT group (n = 20) or a waiting-list control group (n = 20). The ACT group received eight intervention sessions, while the control group received no psychological intervention during the study period. Outcomes were assessed using the Barkley Deficits in Executive Functioning Scale and the Inventory of Statements About Self-Injury. Assessments were conducted at pretest, posttest, and two-month follow-up. Repeated-measures analysis was used to examine group, time, and group-by-time effects. ACT significantly reduced both intrapersonal and interpersonal NSSI functions. Significant group-by-time effects were found for intrapersonal NSSI (F = 11.55, p < .001, partial η² = .23) and interpersonal NSSI (F = 15.02, p < .001, partial η² = .28). ACT also significantly improved executive-function domains, including time self-management, self-organization/problem-solving, self-restraint/inhibition, self-motivation, and emotional self-regulation. Pairwise comparisons showed significant improvements from pretest to posttest and from pretest to follow-up, whereas posttest-to-follow-up differences were not significant, suggesting maintenance of treatment gains. The findings suggest that ACT may be an effective psychological intervention for reducing NSSI behaviors and improving executive-function difficulties in patients with BPD. The results support the use of ACT as an adjunctive clinical approach for targeting emotional dysregulation, maladaptive self-injury functions, and executive dysfunction in this population. Further randomized clinical trials with larger samples and longer follow-up periods are recommended.