en Anxiety and Stress پژوهشي Research Article <span style="font-size:12px;"><span style="font-family:Tahoma;"><span style="line-height:normal"><span style="unicode-bidi:embed"><b><span lang="FR"><span style="color:black">Background and Objective: </span></span></b><span lang="FR">Borderline Personality Disorder (BPD) is characterized by significant challenges in emotion regulation, interpersonal relationships, and self-image, often accompanied by high anxiety sensitivity and difficulties in self-differentiation. The present study aimed to investigate the effectiveness of transdiagnostic treatment on anxiety sensitivity and self-differentiation in individuals exhibiting symptoms of BPD.</span></span></span><br> <span style="line-height:normal"><span style="unicode-bidi:embed"><b><span lang="FR">Materials and Methods: </span></b><span lang="FR">The research employed a quasi-experimental design with pre-test, post-test, and follow-up assessments, incorporating a control group. The statistical population for this study comprised all patients diagnosed with BPD who sought psychiatric consultation in District 4 of Tehran, Iran, in 2024. A targeted sample of 30 participants (15 in each group) was selected based on the inclusion criteria and randomly assigned to either the experimental or control group. The research instruments included the Anxiety Sensitivity Index and Self-Differentiation Questionnaire. The experimental group received 10 ninety-minute sessions of transdiagnostic treatment. Data analysis was performed using repeated measures analysis of variance (ANOVA).<span style="font-family:"Myriad Pro",sans-serif"></span></span></span></span><br> <span style="line-height:normal"><span style="unicode-bidi:embed"><b><span lang="FR">Results:</span></b><span lang="FR"> <span style="letter-spacing:-.2pt">Results indicated that transdiagnostic treatment significantly reduced anxiety sensitivity (F=192.45, P<0.001, &eta;p&sup2;=0.88) and increased self-differentiation (F=201.67, P<0.001, &eta;p&sup2;=0.89) at the post-test stage. This positive effect persisted into the follow-up phase, demonstrating the enduring effectiveness of transdiagnostic treatment.</span></span></span></span><br> <span style="line-height:normal"><span style="unicode-bidi:embed"><b><span lang="FR">Conclusion:</span></b><span lang="FR"> These findings suggest that transdiagnostic treatment can substantially alleviate anxiety sensitivity and improve self-differentiation in individuals with BPD symptoms.</span><span dir="RTL" lang="FA"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span><br> &nbsp; Anxiety, Borderline personality disorder, Self-differentiation, Transdiagnostic therapy 103 109 http://ajnpp.umsha.ac.ir/browse.php?a_code=A-10-1520-1&slc_lang=en&sid=1 Elham Souri sourielhm@gmail.com 10031947532846008743 0009-0007-4412-3044 No Department of Psychology, Ahv.C., Islamic Azad University, Ahvaz, Iran. Fariba Hafezi dr.fariba.hafezi@iau.ac.ir 10031947532846008744 10031947532846008744 Yes Department of Psychology, Ahv.C., Islamic Azad University, Ahvaz, Iran. Amal Sharifi Fard amalsharififard@gmail.com 10031947532846008745 10031947532846008745 No Department of psychology, Ramh.C., Islamic Azad University, Ramhormoz, Iran. Rezvan Homaei rzhomaei@gmail.com 10031947532846008746 0009-0002-8642-1182 No Department of Psychology, Ahv.C., Islamic Azad University, Ahvaz, Iran.