en روان شناسی تکاملی Evolutionary Psychology پژوهشي Original <div style="text-align: justify;"><span style="color:#3366ff;"><span style="font-size:14px;"><span style="font-family:Times New Roman;"><span style="line-height:2;"><b>Objective</b>: <span lang="EN">This study investigated the effects of brief supportive&ndash;expressive psychotherapy on defense mechanisms and the quality of object relations in patients with borderline personality disorder (BPD) and a history of interpersonal trauma. </span><br> <b>Methods</b>: Using a quasi-experimental pretest&ndash;posttest control group design, the study sampled 60 patients from psychological and psychiatric centers in Tehran in 2026, randomly assigned to an intervention or control group. The intervention group received 16 sessions of therapy, while the control group remained on a waiting list. Multivariate analysis of covariance revealed that, after controlling for pretest scores, group membership significantly impacted the dependent variables.<br> <b>Results</b>: Univariate analyses demonstrated that the intervention significantly reduced maladaptive defense mechanisms and improved the quality of object relations, with moderate-to-large effect sizes. These findings suggest that brief supportive&ndash;expressive psychotherapy addresses not only overt clinical symptoms but also deeper processes, such as defensive strategies and relational organization.<br> <b>Conclusions</b>: Clinically, integrating a focus on emotional stability, defensive patterns, self-other representations, and repetitive relational dynamics is beneficial when treating BPD patients with a history of interpersonal trauma.</span></span></span></span></div> Borderline personality disorder, supportive–expressive psychotherapy, defense mechanisms, object relations, interpersonal trauma, psychodynamic psychotherapy 0 0 http://ieepj.hormozgan.ac.ir/browse.php?a_code=A-10-1244-1&slc_lang=en&sid=1 Nafiseh Alsadat Mousavi Nmousavi70@gmail.com 100319475328460013192 0009-0000-1247-9563 Yes Department of Psychiatry, Research Center of Addiction and Behavioral Sciences, Noncommunicable Diseases Research Institute, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.