International Journal of Health Studies2423-65948220211003 Treatment of Automatic Negative Thoughts and Non-suicidal Self-injury (NSSI) Behavior in Borderline Personality Disorder Adolescents: Dialectical Behavior Therapy 3135 10.22100/ijhs.v8i2.900 EN Misagh Norouzi Esfahani MSc in clinical Psychology, Department of Psychology, Isfahan(Khorasgan) Branch, Islamic Azad University, Isfahan,iran . Fatemeh Hasirchaman MSc in counseling, Department of psychology and counseling, kermanshah Branch,islamic Azad university,kermanshah,iran. Vida Shahdadian Naeini Master of science in Positive Psychology, Nain Branch, Islamic Azad university, Iran. Latifeh Sharifpour MSc in General Psychology, Department of Psychology, Faculty of Humanities and Literature, Shahid Bahonar University of Kerman, Kerman, Iran. Nafiseh Boorboor Master of General Psychology, Department of Humanitis، Islamic Azad University Electronic Campus, Tehran, Iran. Javad Seyed Jafari PhD candidate in Psychology, Allameh Tabataba'i University, Tehran, Iran. 20210809 20211003 20210905 Background: About 17 to 80% of borderline personality disorder (BPD) patients suffer repeated NSSI (most frequently, cutting/burning self-injury), while 46 to 92% of BPD patients attempt suicide. This study aimed to investigate the effectiveness of the condensed dialectic behavior in reducing automatic negative thoughts and its positive effects on non-suicidal self-injury (NSSI) behavior in borderline personality disorder (BPD). Methods: A semi-experimental study with pre-and post-tests is going on with both an experimental group and a control group. In 2019, twenty-two BPD adolescents who attended the treatment clinic) Masire Sabz), district 8, Tehran, were divided into two groups. Two questionnaires of automatic negative thoughts and non-suicidal suicide self-injury were administered before and after the intervention. This study employed SPSS 23 with Levene's test, as well as ANOVA to analyze the data. During the intervention group, twelve 90-minute sessions took place with participants in the intervention group, which followed a protocol adapted from a standard DBT protocol for BD participants in the control group waited for a treatment appointment. Results: The results showed that the scores of the intervention group significantly decreased in the Automatic negative thoughts and non-suicidal self-injury after 2 months of the intervention (Pvalue<0.001). Conclusions: It can be concluded that dialectical behavior therapy was effective on automatic negative thoughts and non-suicidal self-injury (NSSI) behavior among borderline personality disorder adolescents. Keywords: Automatic negative thoughts, Non-suicidal self-injury (NSSI) behavior, Borderline personality disorder.