International Journal of Behavioral Sciences

International Journal of Behavioral Sciences

Effectiveness of Mentalization-Focused Dynamic Interpersonal Therapy on Attachment and Self-Differentiation in Patients with Pathological Narcissism: A Single-Subject Design

Articles in Press

Document Type : Original Article

Authors
Amir Shojaei
Nurallah Mohammadi
Habib Hadianfard
Changiz Rahimi
Department of Clinical Psychology, Faculty of Education and Psychology, Shiraz University, Shiraz, Iran
10.30491/ijbs.2026.596205.2347
Abstract
Background and Objective: Pathological narcissism is a common disorder in clinical populations, characterized by two distinct yet related presentations, namely grandiose and vulnerable narcissism, and is often associated with insecure attachment and poor self-differentiation. The aim of this study was to investigate the effectiveness of Mentalization-focused Dynamic Interpersonal Therapy (DIT) on attachment and self-differentiation in patients with pathological narcissism.
Materials and Methods: The research design was a single-subject with baseline, intervention, and follow-up assessments. Six participants with pathological narcissism received Mentalization-focused DIT in weekly individual sessions. The Experiences in Close Relationships-Revised (ECR-R) and the Differentiation of Self Inventory-Revised (DSI-R) were used to measure the study’s dependent variables. Cohen’s d effect size (ES), the Reliable Change Index (RCI), and Percent of Maximum Possible Improvement (PMPI) were used for data analysis.
Results: The results indicated that Mentalization-focused DIT was effective in reducing insecure attachment and increasing self-differentiation. These effects persisted at follow-up, indicating the lasting effectiveness of Mentalization-focused DIT.
Conclusion: These findings suggest that Mentalization-focused DIT can improve attachment status and self-differentiation in patients with pathological narcissism.
Keywords
Pathological Narcissism
Narcissistic Personality Disorder
Attachment
Self-Differentiation
Mentalization-Focused Dynamic Interpersonal Therapy
International Journal of Behavioral Sciences

Articles in Press, Accepted Manuscript
Available Online from 05 November 2026