Introduction
Due to medical progress, the number of elderly people in Iran is increasing rapidly worldwide [1]. In addition to being physically prone to various disabilities, the elderly are also among vulnerable groups regarding mental health. Investigating the factors related to depression as a critical pathogenic factor in late life is essential [2]. This research studied spiritual and social capital and anxiety caused by death. In addition to the direct effect of death anxiety in the elderly, spiritual and social capital also affects their depression [3, 4]. In this research, using the path analysis method to investigate the relationship with depression in the elderly, the appropriateness of the model of the causal relationship of spiritual and social capital with depression through death anxiety was tested, and the model of two groups of elderly with a spouse and without a spouse was compared.
Methods
The statistical population of this research included all elderly men over 60 years old in Tehran in 2019. According to the number of observable variables (4 variables) and data analysis in two groups of elderly people with spouses and those without spouses, 400 elderly people were selected for sampling, a much higher than sufficient volume. Due to the COVID-19 pandemic, traffic restrictions, and the impossibility of filling out the questionnaires in person, the subjects participated in the research online. 
The criteria for entering the study were over 60 years old, being a resident of Tehran City, having good memory and consciousness, having at least fifth-grade education, and consent to participate in the research. After explaining the online questionnaire about how to complete the questionnaires and obtaining informed consent from the subjects to participate in the study, as well as gaining their trust regarding the confidentiality of their information, the questionnaires, which include the Beck Depression Test, the Pajak Social Capital Questionnaire, and the Golparvar Spiritual Capital Questionnaire of the elderly, it was completed by the subjects, and 371 questionnaires were analyzed. The Mean±SD age of the participants in the research was 71.19±8.4, respectively. The current study is correlation type and uses the statistical path analysis method and group comparison. Data collected and analyzed using SPSS software and Amos, v. 23.
The current research is taken from the doctoral dissertation on health psychology, which was reviewed by the ethics committee of the Islamic Azad University of Ahvaz branch and approved (Code: IR.IAU.AHVAZ.REC.1399.106).
Results
The results of the Pearson correlation test show that all research variables have a significant correlation. This indicates the appropriate selection of variables in this research based on the research background and studies conducted in the past. Assumptions of multivariate normality, linearity, multiple collinearities, and independence of errors were tested and confirmed. According to the obtained values, the fit of the overall proposed model tested for all the subjects based on the fit indices of the comprehensive proposed model did not have a good fit after checking the direct and indirect paths of the modified model, and the fit index of the modified model was re-evaluated. Based on the coefficients of the standard parameter and the corresponding level of significance, one of the direct paths of the model was not significant (the direct path of spiritual capital to depression), which was removed from the model, and the suitability of the modified model was re-evaluated. According to the obtained values, the modified model had a good fit and was accepted as the final model (Table 1).


The multi-group analysis method compared two models in two groups of elderly people with and without a spouse. This research investigated the immutability of measurement models through the comparison test of models without restrictions and models with limited weights. The results did not confirm the moderating role of marital status; in other words, in this model, there is no difference between any of the different paths, and the marital status of the elderly does not adjust the paths. Regarding the indirect effect of spiritual capital on depression through death anxiety, due to the non-significance of the direct path, despite the overall significant impact of this relationship, it is fully mediated. Also, for the indirect effect of social capital on depression through death anxiety, due to the significance of the direct path, it can be said that this relationship is partially mediated.
Discussion
Social capital is a source of social relations between family members and society, the increase of which can improve depression in the elderly. Spiritual capital is the strength and influence of attachment to the superhuman force that causes peace, purposeful effort, and hope. The stronger the devotion to spiritual and religious principles, the more hopeful the elderly are when faced with problems, and the less depression occurs [5]. Spirituality answers all the questions related to death, which prevents the anxiety caused by facing death [6]. As a result, reducing this anxiety is less depressive in the elderly. Also, social capital affects people’s approach to death, and having high social capital reduces death anxiety and depression. Online sampling requires particular caution in generalizing the results to all elderly people. Planning to improve the spiritual and social capital of the elderly is recommended.

Ethical Considerations
Compliance with ethical guidelines
The current research is taken from the doctoral thesis of health psychology of Amir Hossein Sharifi, which was reviewed by the ethics committee of the Islamic Azad University of Ahvaz branch and approved with the ethics (Code: IR.IAU.AHVAZ.REC.1399.106).

Funding
The current research is derived from a doctoral thesis and its cost was provided by the authors of the article and it did not receive any funding.

Authors' contributions
All authors contributed equally in preparing all parts of the research.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The authors thank all the elderly who participated in this study


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