Introduction
The physical and functional changes in old age are effective in the social and psychological conditions of the person [1]. Due to issues such as retirement and loneliness, the elderly are prone to suffering from mental problems [2]. Depression is one of the common psychological disorders in old age [3]. Sleep disorders are also one of the most common problems that can cause a decrease in the quality of life, an increase in the risk of mental problems, a decrease in daily performance, and a disturbance in the emotions and motivation of the elderly [4]. Social support is one of the important factors that play a decisive role in improving mental health [5]. People with high social support have higher sense of belonging and self-esteem [6]. Some evidence has shown that a high level of social support encourages people to choose healthier lifestyles [7]. This study aims to examine the relationship between perceived social support and mental health components in the Iranian elderly. 

Methods
This is a descriptive-analytical study that was conducted on the elderly in Tehran, Iran. The inclusion criteria were the ability to complete the questionnaire, the ability to communicate, and not having cognitive impairment. The exclusion criterion was the incomplete return of the questionnaire. Sampling was done by a two-stage cluster method. Using Cochran’s formula, the sample size was estimated to be 420 people at a confidence interval of 95%, considering P=0. 5, d=0. 05, and 10% sample drop. Data were collected using a demographic form, pittsburgh sleep quality index (PSQI), depression anxiety stress scale-21 (DASS-21), and the multidimensional scale of perceived social support (MSPSS). 
The PSQI has 7 items and the total score ranges from 0 to 21; a higher score show the lower sleep quality. The DASS-21 is a self-report tool with 21 items rated on a 4-point scale as 0= Did not apply to me at all, 1= Applied to me to some degree, or some of the time, 2= Applied to me to a considerable degree or a good part of time, and 3= Applied to me very much or most of the time. The total score ranges from 0 to 42, where higher scores indicate higher levels of anxiety, depression, and stress. The MSPSS is a 12-item instrument. This scale measures a person’s perceived level of social support from three sources: family, friends, and significant others. The items are rated on a five-point scale ranging from strongly disagree to strongly agree. The total score ranges from 12 to 60, with a higher score indicating more perceived social support. Data were analyzed using descriptive statistics (frequency, percentage, mean, standard deviation, skewness and kurtosis) in SPSS software, version 25 and inferential statistics (path analysis) in EQS software, version 6.4. In path analysis, stress, anxiety and depression variables were considered as mediating variables. The direct and indirect relationships of social support and the components of mental health (stress, anxiety and depression) with the sleep quality of the elderly were calculated using the path analysis. 

Results
In this study, 69% of the elderly were between 60 and 74 years old (younger elderly), and 31% were between 75 and 90 years old (older elderly). Moreover, 53.8% of the elderly were female and 46. 2% were male; 77.9% were married and 22.1% were unmarried; 12.6% had university education, 19.3% had diploma and 68.1% had lower than high school education; 13.6% had poor economic status, 70.2% had moderate economic status and 16.2% reported good economic status. 
Skewness and kurtosis values for all variables were in the range of -2 to +2; therefore, the data had a normal distribution. The mean scores of depression, anxiety, and stress were 12.9±27.9,11.55±8.8, and 15.05±9.8, respectively. Based on the scores, 19. 3% had mild stress, 10.7% had moderate stress, 16% had severe stress, and 3.3% had very severe stress. Moreover, 6.7% reported mild anxiety, 23.1% moderate anxiety, 14.8% severe anxiety and 19.5% very severe anxiety. Furthermore, 9.5% had mild depression, 20.7% moderate depression, 8.3% severe depression and 6% very severe depression. The mean scores of PSQI and MSPSS were 8.5±2.52 and 47.26±8.5, respectively. Based on the scores, 8. 6% of the elderly had normal sleep quality and 91. 4% had sleep disorders. 
The findings from path analysis showed that social support had an indirect and significant relationship with the sleep quality, while the relationship between the components of mental health (stress, anxiety and depression) with the sleep quality was direct and significant. According to the findings, the direct correlation coefficient between social support and sleep quality was about 0.14 and the indirect correlation coefficient was about 0.48. The total direct and indirect correlation coefficient between social support and sleep quality was about 0.62. In other words, with increasing social support, the amount of change in sleep quality was 62%, and it can lead to better sleep quality. Figure 1 shows the structural model of the study. 
Conclusion
The findings of this study showed a negative and significant relationship between social support and mental health components of the elderly in Tehran, Iran. In other words, higher social support perceived by an elderly person can lead to lower stress, anxiety, and depression and thus better mental health. Social support increases the mental health of the elderly by increasing the sense of intimacy and emotional support. Social support can be effective for subjective assessment of stressors. It can reduce stress and anxiety and promote social adjustment and well-being. By regulating the biological rhythm, it has an effect on maintaining sleep and wakefulness of an elderly person and causes a good quality of sleep in them. 

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the research ethics committee of Shahid Beheshti University of Medical Sciences (Code: R.SBMU.PHNS.REC.1400.070).

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

Authors' contributions
 Implementation of the project, writing the article: Azam Demarchi Lo; design, data analysis, and interpretation: Sakineh Rakhshanderou; Methodology and data interpretation: Mohtsham Ghaffari; Consulting: Masoumeh Sadeghipour Rudsari. All authors reviewed and approved the manuscript.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The authors would like to thank all seniors and their families and the staff of comprehensive health service centers affiliated to Shahid Beheshti University of Medical Sciences for their cooperation in this study.