Introduction
Narcissism has two major phenotypes: grandiose and vulnerable. Grandiose narcissism is pinned by arrogance and pride, extroversion, jealousy, and exploitation and is well covered by DSM criteria. The vulnerable phenotype embraces characteristics like vulnerability, avoidance, introversion, inadequacy, and avoiding interpersonal relations, which are all rooted in fear of rejection [1].
Pincus and Lukowitsky proposed a model for pathological narcissism. According to this model, grandiose narcissism comprises three elements of grandiose fantasy, exploitative, and self-sacrificing/self-enhancement. Vulnerable Narcissism comprises four elements of contingent self-esteem, hiding the self, devaluating, and entitlement rage [13]. The pathological narcissistic inventory (PNI) evaluates narcissism based on this model.
On the other hand, the short version of PNI (PNI-BF) is compatible with its long version. Moreover, it enhances researchers’ ability to inspect pathological narcissism in a shorter period [13]. A study indicates that the Iranian population has certain characteristics that differentiate it from western and other eastern societies [16, 17]. The research findings also show conflicting information about narcissism among men and women in the Iranian population [16].
Therefore, the present study was conducted to answer two questions: 
1. Does the brief form of pathological narcissistic inventory have validity and reliability in the sample of Iranian students?
2. Do men and women differ significantly from each other based on the personality traits of pathological narcissism?
Methods
The present research is a descriptive study performed on 659 students in different degrees and fields in the 2018-2019 academic year. They were selected using the cluster sampling method. The face validity was calculated by administering the questionnaire to a group of 30 students. The convergent validity was assessed using the test of self-conscious affect (TOSCA-3), the narcissistic personality inventory (NPI), the Beck depression inventory (BDI), and the Rosenberg self-esteem scale (RSE). The reliability was also investigated through testing and retesting in a group of 42 students from the target population at a 1-month interval. The Pearson correlation was used to investigate the convergent validity and reliability. The Cronbach α was also used to investigate the internal consistency of the questions. Confirmatory factor analysis was also implemented to evaluate the 7-factor structure of the inventory. Differences between means regarding features of narcissistic personality in genders were evaluated using multivariate analysis of variance. All data analysis was performed using SPSS v. 20 or LISREL v. 8.8 software. 
Results
To obtain the face validity, the impact score of every item was calculated. Findings indicate that all impact scores of questions were above 1.5. Internal consistency was calculated by obtaining Cronbach α values, and the findings are as follows: 0.75 for exploitative, 0.78 for self-sacrificing/self-enhancement, 0.85 for grandiose fantasy, 0.8 for contingent self-esteem, 0.73 for hiding the self, 0.79 for devaluating and 0.66 for entitlement rage.
The results of the retest with a 1-month interval indicate that the Pearson correlation coefficients are 0.87 for exploitative, 0.89 for self-sacrificing/self-enhancement, 0.81 for grandiose fantasy, 0.87 in contingent self-esteem, 0.81 on hiding the self, 0.9 on devaluating, and 0.86 on entitlement rage which was all significant at P=0.01 level. Also, the correlation calculated between the two general factors of grandiose and vulnerable narcissism with the test of self-conscious affect, Beck’s depression inventory, and Rosenberg’s self-esteem scale was significant and non-significant in relation to the narcissistic personality inventory (Table 1). 


Confirmatory factor analysis was as well run to investigate the 7-factor structure of pathological narcissism. The following model fit indices were obtained on the 7-factor model of PNI-BF: GFI=0.8, IFI=0.94, CFI=0.94, RMSEA=0.09, and AGFI=0.76. The reported index of the Chi-squared divided by the degree of freedom (χ2/df) equaled 6.5, which is more than satisfactory (Table 2, Figure 1). 


Comparison of narcissism scores among different genders showed that the grandiose scale was significantly higher in men (F [1,629] =8.08, ŋ2=0.013, P= 0.005), but there was a non-significant difference between men and women in terms of vulnerability scale (F [1,629]=3.35, ŋ2=0.004, P=0.06).
Discussion
The findings confirm the psychometric characteristics of the PNI in the public university students of the Tehran population. The present research establishes that beta pride negatively correlates with contingent self-esteem and devaluating subscales. Beta pride, based on achievements (I am proud of what I have achieved), is due to internal, controllable, and unstable attribution [30, 40, 41]. As expected, vulnerable narcissistic traits are negatively correlated with beta pride.
Externalization correlates with grandiosity and vulnerability scales. Moreover, shame-proneness correlates with grandiosity and vulnerability scales. Because of multiple instances of externalization of shame-related emotions, there is an extensive overlap between shame-related scales and externalization [42, 43]. Guilt-proneness is also a scale that shows a significant negative correlation with the exploitative subscale [13]. It can be expected that, in case of experiencing guilt, individuals would exploit others to a lesser extent, and chances of using others to reach their goals would be restricted [46]. 
Comparing genders on grandiosity revealed that men scored significantly higher on the construct while there was no significant difference between the genders on vulnerability. This finding is also in line with the study of Ghorbani et al. [18].

Ethical Considerations
Compliance with ethical guidelines
This research was approved by Iran University of Medical Sciences with code of ethics 1395.95-03-185-28539.

Funding
This research was financially supported by the Research Vice-Chancellor of Iran University of Medical Sciences (Faculty of Behavioral Sciences and Mental Health).

Authors contributions
Conceptualization: Afsana Akhani and Ahmad Ashuri; Research and investigation: Ahmad Ashuri, Afshana Akhani and Fatemeh Hassanzadeh; Edited and finalized by: Fateme Hassanzadeh and Afshana Akhani.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
We extend our sincere thanks to Schoenleber as well as Pincus for their scientific help and guidance. We are also grateful for the financial support from the Research Administration of Iran University of Medical Sciences.
 

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