Introduction
The coronavirus disease 2019 (COVID-19) pandemic has affected the general population, including the hospital medical staff and exposed them to psychological disorders. Many studies have shown the dramatic growth of post-traumatic stress disorder (PTSD) in medical staff during the COVID-19 pandemic. This psychological disorder occur in individuals experienced traumatic events, although many resilient individuals may not have PTSD after experiencing such events. During the COVID-19 pandemic, resilience and higher capability to manage personal and systemic stress are strong protective factors. According to a study, individuals with high anxiety sensitivity (AS) had more scores related to intrusion of disturbing thoughts, avoidance of relevant stimuli, changes in cognitive and emotional symptoms, and severe PTSD. Since few coherent studies have examined the aforementioned variables simultaneously, further detailed studies are needed to detect the variables associated with PTSD during the COVID-19 pandemic to provide a perspective on indigenous and demographic differences. In this regard, the present study aims to determine the relationship between PTSD with AS and resilience in medical staff during the COVID-19 pandemic in north of Iran.
Methods
This is a analytical cross-sectional study. The study population consists of all physicians and nurses with contractual, non-contractual, and permanent employment working in the COVID-19 wards of Razi and Poursina hospitals in Rasht, Iran (n=150). Based on Krejcie and Morgan’s table, the sample size was determined 106, and samples were selected using a convenience sampling method and based on the inclusion criteria. The data collection tools were a demographic form, Weathers et al.’s Post-Traumatic Stress Disorder Checklist, Reiss et al.’s Anxiety Sensitivity Index, and the Connor-Davidson Resilience Scale which were completed online for two months in 2021. Of 106 samples, 94 completed the questionnaires. The collected data was statistically analyzed in SPSS software, version 25 using descriptive statistics, Pearson correlation test, and multiple linear regression analysis.
Results
The participants’ mean age was 34.87 ± 8.56 years, and there were 87.2% female and 12.8% male. Regarding the level of education, 4.2%, 17%, and 78.7% of the participants had PhD degree, master’s degree, and bachelor’s degree, respectively. No significant difference was observed in the mean PTSD scores between male and female staff and between different age groups. The participants in different educational groups had no significantly different PTSD scores, either (P>0.001). However, there were a significant negative relationship between PTSD and resilience scores (r=-0.405, P=0.001) and a significant positive relationship between PTSD and AS scores (r=0.633, P=0.001). 
The summary of the regression analysis results in Table 1 showed that age, gender, and level of education had no significant relationship with PTSD score (P>0.001).


PTSD was significantly decreased by the increase of resilience (B=-0.208; P=0.004) and significantly increased by the increase of AS (B=0.574; P=0.001). Resilience (β=-0.229) and AS (β=0.562) significantly predicted PTSD. According to the β values for these two variables, if other remained constant, one unit of change in resilience and AS would cause a change in PTSD by -0.239 and 0.562, respectively (P 0.05).
Discussion 
The findings revealed that resilience could help the medical staff have psychological stability and adaptability during the pandemic and reduce their vulnerability to PTSD. Resilient individuals may have higher ability to adapt to adverse conditions and overcome threats. Based on spiritual factors, tolerance of negative effects, self-control, acceptance of situations, and self-sufficiency, resilient individuals have psychological safety. During the COVID-19 pandemic, medical staff with high AS are likely to misinterpret their physical symptoms to be COVID-19 symptoms and feel threatened and anxious. They may be preoccupied with catastrophizing or feeling that a disease is imminent. Although each person has a different psychological background, it is important to provide mental health tools with a preventive approach to the public. Longitudinal studies with different samples are recommended to investigate the relationships among the study variables during the pandemic by considering the underlying and causal factors.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of the Guilan University of Medical Sciences (Code: IR.GUMS.REC.1400.039).

Funding
There was no funding from any governmental, private, or non-profit organizations.

Authors' contributions
 The authors contributed equally to designing, writing, and conducting the research.

Conflicts of interest
The authors declare no conflict of interests.

Acknowledgements
The authors would like to thank the managers, supervisors, and all medical staff of Poursina and Razi hospitals in Rasht, Iran for their cooperation, and Ms. Pourhabibi for her guidance on the research findings.

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