Introduction
It is important to understand the patient’s personality organization when planning psychotherapy and observing its results. Kernberg recognized three levels of personality organization: neurotic, borderline, and psychotic. Borderline personality disorder (BPD) is a common mental disorder that is associated with high rates of suicide, severe functional impairment, high rates of comorbid mental disorders, high use of treatment, high use of defense mechanisms, and high cost burden on the healthcare system. Defense mechanisms are automatic regulatory processes that act to reduce cognitive abnormalities and minimize sudden changes in reality and perception of threatening events. Studies have indicated the effectiveness of psychotherapy methods for BPD patients, including the transference-focused psychotherapy (TFP), whose goal is to change symptoms and interpersonal problems through structured psychological care that corrects mental representations of self and others. This process leads to behavior conduction. Another treatment option for these patients is acceptance and commitment therapy (ACT). ACT begins with fundamental research on human distress and establishes a general psychological model, collecting related interventions. 
There are several organized psychotherapies for BPD, but none of them have priority over the others in reducing symptoms. It is essential to explore why TFP and ACT are unique. In fact, we choose these types of treatment because their goals are beyond symptom reduction. The main question is whether TFP and ACT are effective in addressing personality organization and defensive styles in people with BPD.

Method
In this randomized clinical trial, the study population consisted of all individuals with BPD referred to Zare Psychiatric Hospital and Khaney-e Ma’na Clinic in Sari, north of Iran, in 2020 (n=32). Those who met the entry criteria were selected using a convenience sampling method (n=11) and were randomly assigned to TFP (n=4), ACT (n=4), and control (n=3) groups using a lottery method. The questionnaires included Kernberg’s Inventory of Personality Organization (IPO) and Defense Styles Questionnaire. The TFP and ACT interventions were provided for one year, two sessions per week, each for 48 minutes, following the formal treatment protocols, done by trained therapists. Data were collected before the interventions, at the first session, during the 40th session, during the 80th session, at the 100th session (after intervention), and six months after interventions (follow-up). The TFP sessions were conducted under the supervision of two experts—one from Iran and one from Sweden. For ACT, another supervisor from Iran was also involved. Both therapy sessions adhered to the official guidelines established for these treatments.

Results
Figures 1, 2, 3, and 4 show the mean scores of the study variables for three groups. There was a statistically significant difference in the total IPO score among the groups (P=0.023). Regarding the IPO domains, the difference was also significant in primitive psychological defences, reality testing, and identity diffusion (P<0.05). There was no significant difference in the immature defensive style (P=0.603), but a significant difference was found in the mature defensive style (P=0.041) and neurotic defensive style (P=0.366).










Conclusion
The findings demonstrated that both TFP and ACT were effective in improving personality organization in patients with BPD. Additionally, both TFP and ACT have a significant impact on the defense styles of these patients. For TFP, the effectiveness is observed in mature, neurotic, and immature defensive styles. In contrast, ACT only affects immature and mature defensive styles. It is recommended that future studies combine TFP and ACT and use larger samples to obtain more generalizable results.

Ethical Considerations

Compliance with ethical guidelines
This study was approved by the committee of Birjand University of Medical Science (Code: IR.BUMS.REC.1399.245) and was registered by the Iranian Registry of Clinical Trails (ID: IRCT20131007014928N7).

Funding
This article was extracted from the PhD thesis of Fatemeh Fathi at Islamic Azad University Birjand, Birjand. This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

Authors contributions
Conceptualization and initial draft preparation: Fatemeh Fathi; Supervision: Shahram Vaziri and Mehdi PourasghR. Methodology: Maryam Nasri.

Conflicts of interest
The authors declare no conflict of interest

Acknowledgments
The authors would like to thank all participants for their cooperation in this study.