Separation anxiety disorder is one of the most common mental disorders in teenagers that causes severe physical and mental disorders. The aim of this study was investigated effect of Intensive Dovanlo's short-term Daynamic Psychotrapy on The Quality of Object Relations and Defense Mechanisms in Adolescents White Separation Anxiety Disorder. This study was experimental method with pre-test-post-test design with a control group. The study’s population consisted of all male students of the second High school with separation anxiety disorder from khalkhal city during the academic year 2021-2022. Among these, 30 number of students with separation anxiety disorder based on March et al.'s separation anxiety questionnaire (1997) and the structured clinical interview and other inclusion criteria the research were selected and random assignment and placed in two experimental and control groups (15 people in each group).The experimental group was trained 10 sessions of 60 minutes under a short-term in Dovanlo's short-term Daynamic Psychotrapy. Bell's (1995) thematic relationship questionnaires and Andrews et al.'s (1993) defense mechanisms questionnaires were used for both groups in the pre- and post-test stages. Research data were analyzed by multivariate covariance analysis. The results showed that Dovanlo's short-term Daynamic Psychotrapy can significantly improve the quality of Object relationships and reduce Defense Mechanisms in Adolescents. Based on this, the using of Dovanlo's short-term Daynamic Psychotrapy can help students with separation anxiety disorder in reducing psychological problems and increasing the quality of relationships. Keywords: Dovanlo's short-term Daynamic Psychotrapy, Object Relations, Defense Mechanisms, Separation Anxiety Disorder. Extended Abstract Introduction Separation anxiety disorder is considered to be one of the most common mental disorders in adolescence, which affects 6-20% of children and adolescents in developed countries (Hannesdottir, 2018). Among the factors related to the phenomenon of anxiety, two important cases can be mentioned. One is object relations, which means the person's representations of himself and others and the factors associated with these representations (Handelzalts et al., 2014) or the person's capacity to establish relationships in the early years of life (Kelly, 2014). Another variable is the defense mechanisms that the adolescent with separation anxiety disorder resorts to underdeveloped and maladaptive defense mechanisms in order to control his anxiety due to the experience of rejection from parents and great anxiety in interpersonal situations (Giuseppe et al., 2019; Ciocca, et al., 2017; Abbasi et al., 2014). Findings suggest that Intensive Dovanlo's short-term dynamic psychotherapy is an effective treatment for adolescents with anxiety disorders who did not respond adequately to previous standard treatments (Çitak et al., 2021; Bosh & Miler, 2015; Keefe et al., 2014). In this treatment, it is on the unconscious that by breaking the resistance and by producing mental images and vivid memories of the unconscious content, light shines on the core structure of the unconscious (Glisson et al., 2018). Despite the importance of thematic relationships and defense mechanisms in separation anxiety and the effect of intensive short-term dynamic psychotherapy, researches about these two variables in adolescents with separation anxiety disorder are few, and on the other hand, the effectiveness of this treatment method in the society of men with addiction, borderline personality disorder, Obsessive Compulsive Disorder, Depression, Social Anxiety, Generalized Anxiety and Separation Anxiety. This is while teenagers also suffer from separation anxiety disorder and experience many problems in family relationships, school, social functioning, isolation, and lack of motivation. Research Question Does Intensive Dovanlo's short-term dynamic psychotherapy have an effect on the quality of object relations and defense mechanisms of adolescent boys with separation anxiety disorder? Literature Review Mikaili and Moulai (2019) stated that there is a significant negative relationship between separation anxiety disorder and developed defense mechanisms, and a significant positive relationship between neurotic and underdeveloped defense mechanisms. As a result, underdeveloped defense mechanisms were confirmed as predictors of separation anxiety disorder. The results of Meskarian et al.'s research findings (2015) indicated that through short-term intensive dynamic psychotherapy, with a focus on communication patterns, while improving the quality of thematic relationships, anxiety decreased, which shows the usefulness of this treatment method. Prout et al. (2019), stated that psychodynamic therapy can target maladaptive defense mechanisms and improve self-regulation capacity, increase flexibility, and improve interpersonal relationships. Parisuz et al. (2019), observed that short-term intensive dynamic psychotherapy reduces negative emotions and improves interpersonal processes. Methodology The current research is an experimental study with a pre-test-post-test and control group design in terms of practical purpose and in terms of research design. The statistical population of the research included all male students of the second secondary school with separation anxiety disorder in Khalkhal city in the academic year of 1400-1401. Multi-stage cluster random sampling method was used to collect data after obtaining a code of ethics (IR.GULAN.REC.1401.007) from the University of Guilan. Thus, firstly, all secondary schools of Khalkhal city (8 high schools and conservatories) were selected, and in the next step, 3 classes of 10th, 11th, and 12th grades were randomly selected from each school. Then the members of these classes (480 students) were examined with the Multidimensional Anxiety Scale (March et al., 1997) and 34 people who obtained a cutoff score ≥ 60 were identified, then a structured clinical interview of anxiety symptoms was conducted with them. A structured Clinical Interview for Separation Anxiety Symptoms (Shear et al., 2002) was conducted and among them, 30 teenagers with separation anxiety disorder were randomly placed in two experimental and control groups (15 people in each group) and the experimental group had 10 sessions and each session lasted for 90 minutes one by one and according to a predetermined schedule, they were subjected to Intensive Dovanlo's short-term dynamic psychotherapy. After that, the Bell Object Relations Inventory (1995) and the Defense Style Questionnaire (Andrews et al., 1993) were conducted for both groups. It is necessary to explain that at the beginning, in a briefing meeting and stating the objectives of the research, consent was received from the students and their parents to participate in the research, and the researcher assured the participants that all the materials presented in the therapy sessions and the results of the questionnaires will be confidential. In this research, the treatment program was carried out by the researcher who received the necessary training in this field. Results Table 1. The results of MANCOVA of the sub-scales of object relationship OP Eta P F MS DF SS variables 1 813/0 001/0 21/104 13/139 1 13/139 Egocentricity group 52/0 156/0 046/0 43/4 03/9 1 03/9 Alienation 1 541/0 001/0 24/28 06/41 1 06/41 Insecure Attachment 77/0 246/0 010/0 83/7 44/7 1 44/7 Social Incompetence Table 2. The results of MANCOVA of subscales of defense mechanisms OP Eta P F MS DF SS variables 1 591/0 001/0 05/36 60/1472 1 60/1472 Mature styles group 1 778/0 001/0 69/87 53/1975 1 53/1975 Neurotic styles 1 566/0 001/0 64/32 18/1495 1 18/1495 Immature styles Discussion The results showed that Intensive Dovanlo's short-term dynamic psychotherapycan significantly improve the quality of object relationships and reduce the maladaptive defense mechanisms of adolescents with separation anxiety disorder.The studies of Meskarian et al. (2015), Parisuz et al. (2019), and Prout et al. (2019) are in line with the findings of this research.In explaining this finding, it can be said that in this method, the therapist by establishing a sincere and safe environment, building capacity, and rebuilding primitive defenses, stimulates the unconscious therapeutic alliance, which is an antidote to alienation, insecure attachment, social incompetence, and self-centeredness.Also, in the treatment sessions, with the experience of intimate relationships, the capacity of emotional insight into past problems is acquired, and it reduces self-centeredness and social incompetence caused by previous bitter experiences.Dynamic psychotherapy creates more adaptive defense styles and the patient's pathological symptoms improve due to the change in his defense styles.In this way, in this therapeutic method, the teenager learns to experience his feelings and becomes aware of the defenses and behavior that cause the suppression of feelings, therefore, he does not see the need to use inappropriate defenses in various situations to hide his feelings. Conclusion In general, it can be said that since adolescents with separation anxiety disorder, due to the fear of rejection and loss of loved ones, experience problems in recognizing and describing emotions and communicating emotions according to the conditions, in short-term intensive dynamic psychotherapy, the capacity for insight is acquired regarding past problems and it reduces self-centeredness and improves subject relationships. On the other hand, in this therapeutic approach, people face their feelings and learn more logical ways to cope with their experiences and feelings, which reduces incompatible mechanisms. Due to time limitations, the follow-up period was omitted, which can lead to the generalization of the results with caution, therefore, it is suggested that future researches be conducted with the follow-up period in order to determine the effect of this intervention on the considered variables more precisely. Acknowledgments The authors of the article sincerely thank and appreciate the cooperation and assistance of all education officials of Khalkhal City and especially the patient students participating in this research.