Introduction: The tourism industry, as one of the most important pillars of economic, social, and cultural development, plays a key role in creating job opportunities, strengthening local infrastructure, and improving the quality of life in communities. This industry, which ranks as the third-highest revenue-generating sector globally after oil and gas and chemical industries, has particularly garnered the attention of policymakers and planners in developing countries. Among its various branches, health tourism holds a special place due to its combined medical, economic, and social benefits. This branch of tourism, encompassing three main subcategories—wellness tourism, therapeutic tourism, and medical tourism—aims to improve individuals' physical and mental health while attracting foreign exchange revenues, presenting itself as an effective tool for sustainable development.
Iran, with its diverse natural resources such as hot springs and mud therapy sites, advanced medical infrastructure, affordable healthcare costs, and highly skilled medical professionals, possesses significant potential to become one of the leading hubs for health tourism in the world. Additionally, Iran's excellent geographical position and historical and natural attractions further enhance its appeal as a health tourism destination. However, challenges such as the lack of coherent management, weaknesses in international advertising, and insufficient infrastructure development have hindered the optimal utilization of these capacities. Meanwhile, regional competitors like the United Arab Emirates, Turkey, and Jordan have captured a significant share of the global health tourism market through extensive investments and targeted marketing. This regional competition underscores the urgency of designing operational strategies and macro-policies in Iran.

Methodology: The main purpose of this research is to identify the factors influencing the sustainable development of health tourism in Iran and to present a comprehensive model based on the system dynamics approach. This applied study analyzes causal relationships and mutual feedback among key variables, utilizing dynamic modeling to simulate system behavior and predict various scenarios.
In this study, key variables such as healthcare infrastructure, the number of health tourists, service quality, investment, and international advertising are identified and analyzed using causal-loop diagrams. The stock-and-flow model was designed and implemented with Vensim software. Various scenarios are simulated to analyze system behavior. Model validation is conducted through sensitivity analysis, structure testing, extreme condition examination, and comparison of predicted results with real data. Additionally, expert feedback from the health tourism sector was utilized to refine and improve the model.

Results and Discussion: In this study, the scenarios of increasing investment in security and welfare facilities, increasing the advertising budget, and enhancing medical services and facilities have been presented.The dynamic hypothesis of the study suggests that increasing investment in healthcare infrastructure, improving service quality, and effective advertising lead to the development of health tourism, economic growth, and strengthened infrastructure. However, negative factors such as environmental pressure and a shortage of specialized personnel may hinder this process. This modeling facilitates the analysis of system complexities and the identification of optimal policies for sustainable development.

Conclusion: In this paper a stock-and-flow model was designed, enabling the simulation of system behavior over different time periods. In the simulation phase, various tests, including sensitivity analysis, comparison with real-world data, and boundary condition analysis, were conducted. The results of these tests demonstrated high accuracy and validity of the model. Using this model, three key policy scenarios were defined and simulated to analyze different impacts on the system. The findings indicated that focusing on improving medical facilities and investing in international advertising are among the most effective strategies for enhancing Iran's position in health tourism.
The study's findings highlighted that the sustainable development of health tourism is significantly influenced by variables such as investment in infrastructure, the quality of medical services, international advertising, and interdepartmental coordination. Feedback loop analysis revealed that positive feedback loops, such as increased revenue from tourists and reinvestment in infrastructure, play a crucial role in achieving sustainability. In contrast, negative feedback loops, such as declining service quality due to reduced investment, can limit the development of this industry.
Sensitivity analysis showed that targeted advertising and revenue per tourist are the most influential variables in attracting health tourists. Moreover, a comparison of findings with previous research indicated that the results of this study are consistent with prior studies. For instance, the research by Figueiredo et al. (2024) also confirmed the impact of advertising on attracting health tourists. Similarly, the findings of Tsakouropoulos et al. (2023) regarding the importance of medical service quality align with the results of this study.