Introduction
People with substance use disorders (SUDs) suffer from many comorbid psychological problems such as externalizing spectrum disorder [7, 8], which include disruptive, impulse-control, and conduct disorders [1]. It seems that SUDs and some personality traits such as high levels of neuroticism, disinhibition, and antagonism and low level of conscientiousness are strongly related to each other due to possible common etiology and spectral relationships [13, 14]. In this regard, the Personality Disorders Work Group of the DSM-5 has provided an alternative model of personality disorders (AMPD) which may have high clinical applicability for explaining the pathological personality traits in people with SUDs [17]. The AMPD is an expanded model of the five-factor model of personality (FFM) that specifically identifies maladaptive variants of personality traits [13, 18, 19], including five higher-order domains: Negative affectivity, detachment, antagonism, disinhibition, and psychoticism), and 25 lower-order domains (facets) that help clarify the higher-order domains [1, 20].
Identifying the common factors in the dimensional link between psychological disorders and pathological personality traits is of great importance. In many studies, transdiagnostic factors have been mentioned the mediators of this dimensional link [21, 22, 23]. In recent studies, impulsivity has been reported as one of the main transdiagnostic risk factors that mediates the relationship between pathological personality traits and externalizing spectrum disorders in people with SUDs [24, 25, 26]. Although various studies have emphasized the relationship between pathological personality traits and externalizing spectrum disorders in people with SUDs, the role of mediators involved in this relationship has been less investigated. Considering the research gap and lack of studies in this field, the present study aimed to explain this relationship with an emphasis on the role of impulsivity as a mediator in men with SUDs, which can have practical implications in treating and preventing SUDs.

Methods
This is a correlational cross-sectional study using the structural equation modeling (SEM). The study population consists of men with a history of SUDs who were outpatients in the drug addiction treatment centers or Ghods Psychiatric Hospital in Sanandaj, Iran, of whom 349 were selected using a convenience sampling method. The inclusion criteria were age 18-55 years, a history of SUDs, at least an elementary school education, and willingness to participate in the study. The exclusion criteria were any physical disability or sever psychiatric disorders such as psychotic disorders that avoid completing the questionnaires, and not answering more than 30% of items. The instruments were the personality inventory for DSM-5 (PID-5), the externalizing spectrum inventory (ESI), and the Barratt impulsivity scale (BIS). Data were analyzed in SPSS software, version 22 and AMOS version 24.

Results
In this study, participants had a mean age of 34.72±7.36 years. The majority of them had elementary school education (43%) and were single (47%), with opioid dependency (35%). The results showed that the PID-5 pathological personality traits of antagonism (β=0.593, P=0.001), detachment (β=0.513, P=0.001), disinhibition (β=0.616, P=0.001), negative affectivity (β=0.565, P=0.001), and psychoticism (β=0.541, P=0.001) had significant and positive correlations with externalizing spectrum disorders (Table 1). 


According to the results in Table 2, the study model had good fit to the data.


The five pathological personality traits had a direct and significant relationship with externalizing spectrum disorders (P=0.001). Furthermore, the bootstrap test results showed that BIS dimensions of attention, motor and non-planning impulsivity mediated the relationship between the pathological personality traits and externalizing spectrum disorders in men with SUDs.

Conclusion
The results showed that the five AMPD pathological personality traits have direct relationship with externalizing spectrum disorders in men with SUDs. Furthermore, the BIS domains of cognitive, motor and non-planning impulsivity can mediate the relationship between the pathological personality traits and externalizing spectrum disorders in men with SUDs. Therefore, more attention to these traits are recommended for prevention and treatment of SUDs.

Ethical Considerations
Compliance with ethical guidelines
All ethical principles, such as obtaining informed consent from the participants, the confidentiality of their information, and their right to leave the study, were considered. Ethical approval was obtained from the Research Ethics Committee of University of Kurdistan (Code: IR.UOK.REC.1400.003).

Funding
This article was extracted from the master’s thesis of Iman Parniani at the Department of Clinical Psychology, University of Kurdistan, Iran. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for profit sectors.

Authors contributions
Supervision, Conceptualization, Methodology, Writing original draft, Review & Editing: Mehdi Zemestani; Investigation, Project administration, Data curation, Formal analysis: Iman Parniani.

Conflicts of interest
The authors declare no conflict of interest. 

Acknowledgments
The authors would like to thank the addiction treatment centers and Ghods Psychiatric Hospital in Sanandaj and all men who participated in this study for their support, cooperation, and assistance.

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