1. Introduction
Peer victimization is the experience among children of being a target of the aggressive behavior of other children. Peer victimization is prevalent and can lead to mental health difficulties [4]. Among the outcomes of peer victimization, depression has been reported more; however, not all adolescents who experience victimization develop depression. Thus, identifying the mechanisms through which peer victimization is related to depression is important for development of interventions to reduce the negative impacts of peer victimization. Two potential mechanisms are external shame and self-compassion. External shame refers to how one perceives oneself as unattractive to others and, therefore, has a feelings of being rejected and vulnerable to attacks from others. It has a strong association with depression [19, 20]. Since adolescents are more sensitive to the images they create in others and being victimized by peers is an experience that involves humiliation, this phenomenon can make adolescents vulnerable to external shame and expose them to depression. However, studies have shown that shame has a mediating role which suggests that there are other psychological mechanisms. Another potential mechanism is self-compassion. A self-compassionate person has a realistic awareness of his/her strengths and weaknesses, sees them as part of the common experience in human beings and takes a balanced perspective on them [26, 27]. Peer victimization is associated with emotion dysregulation [32]. Thus, the development of self-compassion as an effective emotion regulation strategy can be impaired in victims. To our knowledge, no study on the role of self-compassion in the context of peer victimization has been conducted so far.
The mediating role of external shame and self-compassion can be well justified based on the compassionate mind theory of Gilbert. According to theory, humans are born with an innate desire to belong to a group and create positive emotions in others. Experiencing hostile environment can activate the threat system in which humans use safety strategies to protect themselves but these strategies may have unintended consequences such as rumination, feeling of unworthiness and depression. What sustain this cycle going is shame, self-attack and reduced self-compassion [40, 41]. Based on this approach, the present study aims to examine the mediating role of external shame and self-compassion in the relationship between peer victimization and depression.

2. Methods
This is a descriptive correlational study. The study population consists of all middle-school students in Shahin Shahr city, Isfahan, Iran during 2018-2019. Samples were selected using a multi-stage cluster sampling method. The sample size was determined 300 considering a sample drop and given that there is need for at least 20 cases for each parameter [43]. To collect the data, Multidimensional Peer-Victimization Scale, Other As Shamer Scale, Self-Compassionate Scale-Short Form, and Mood & Feeling Questionnaire were used [44, 46, 48, 50]. The data were analyzed in SPSS V. 19 and AMOS V. 20 applications.

3. Results
Pearson’s correlation test results showed a significant correlation (Table 1).



The results of path analysis showed that the direct paths between the study variables were significant except between peer victimization and depression; therefore, the path between them was removed (Figure 1).




The evaluation of measurement model by using fit indices demonstrated that the measurement model had a good fitness (Table 2).



To evaluate the mediating effect, the Bootstrap test was used. The results showed that all of the three indirect paths were significant (Table 3).




4. Discussion and Conclusion
The purpose of this study was to investigate the mediating roles of external shame and self-compassion in the relationship between peer victimization and depression. Findings showed that the study model had a good fitness. That is, students experiencing higher levels of peer victimization reported higher levels of external shame, which was associated with lower levels of self-compassion and depression. The results are consistent with the results of Irwin et al. Strom et al. Duarte et al. Jativa and Cerezo, and Zhang et al. [23, 24,25, 35, 37]. Due to the increase in the sense of belonging and metacognitive abilities in adolescence and given that youth feel humiliated by peer victimization, the victim may think that others have a negative perceptions of him/her. According to Gilbert, victimization by peers may create a hostile environment, stimulate the threat system and activate the fear of getting hurt by others [40]. External shame is associated with the secretion of cortisol (a steroid hormone related to the threat system) and accompanied with adopting coping strategies (avoidance, refusing to ask for help) which intensify depression. The victims may learn self-attack from a bully and lead to lack of self-compassion in them. People with low self-compassion are more likely to engage in self-criticism [20] and judge their negative aspects which may be the same aspects targeted in peer victimization. Research has shown that self-criticism is one of important causes of depression, even years after becoming a victim.
These results of this study may help explain why peer victimization does not put anyone in a vulnerable position. In fact, peer victimization is associated with depressive symptoms, through believing in the negative judgment of others and consequently, through a kind and balanced attitude towards one’s shortcomings and weaknesses. The importance of interventions that emphasize on reducing shame and increasing self-compassion in coping with peer victimization and treating depression can be the potential clinical implications of the results of this study.

Ethical Considerations
Compliance with ethical guidelines
This study has been approved by the ethics committee of Iran University of Medical Sciences (Code: IR. IUMS. REC.1398.099). According to research ethics, a written consent must be obtained from the parents, if the subjects are children (under 18 years of age). Also, one of the exclding criteria was the withdrawal of the participant from continuing the research. They were also assured about the confidentiality of their information and were free to leave the study whenever they wished, and if desired, the research results would be available to them.

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors. 

Authors contributions
Conceptualization: All authors; Methodology: Soheila Yaghoubi and Ahmad Ashouri; Date analysis: Soheila Yaghoubi and Ahmad Ashouri; Research: Asma Aqebati and Soheila Yaghoubi; writing – original draft: Behrouz Birshak and Soheila Yaghoubi; Writing – review & editing: Asma Aqebati and Soheila Yaghoubi; Resources: Soheila Yaghoubi and Asma Aqbati; Supervision and coordination: Behrooz Birshak.

Conflicts of interest
The authors declare no conflict of interest.

Acknowledgements
The authors would like to thank the Education Organization of Isfahan and all participants for their cooperation.

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