Introduction: Psychological stress is one of the most common health problems in modern life. People experience different types of stress and pressure every day, which may affect their physical and mental health. The effects of stress are not limited to emotional well-being; they can also influence several body functions, especially the immune system, which is the body’s main defense against diseases and infections. The Relationship Between Psychological Stress and the Immune System: When a person experiences psychological stress, the body activates its stress response, leading to the release of hormones such as cortisol and adrenaline. These hormones help the body respond to difficult situations. However, prolonged exposure to high levels of these hormones may negatively affect immune system functions. Chronic stress can influence the activity of immune cells, including white blood cells, which play an important role in fighting viruses and bacteria. It may weaken certain immune responses and increase the body’s susceptibility to infections. Furthermore, long-term stress may increase inflammation in the body by disturbing the normal regulation of immune responses. It may also affect the body’s ability to recover and fight diseases. The Effects of Stress on Human Health: The effects of psychological stress are not limited to the immune system. Stress can also affect sleep quality, appetite, and concentration. It may cause persistent fatigue, headaches, and digestive problems. In addition, poor sleep and unhealthy eating habits caused by stress may have negative effects on immunity because the body needs adequate rest and essential nutrients to maintain normal functions. Prevention and Stress Management: The negative effects of psychological stress can be reduced by following a healthy lifestyle.This includes regular physical exercise, getting enough sleep, and eating a balanced diet rich in vitamins and minerals. Deep breathing exercises, meditation, and relaxation techniques can also help reduce stress and improve mental health. Spending time with family and friends and receiving social support are also important factors in maintaining psychological well-being. Conclusion: In conclusion, chronic psychological stress is one of the factors that may negatively affect the immune system and overall human health. Therefore, taking care of mental health, managing daily stress, and following a healthy lifestyle can help support immune function and reduce the risk of diseases. This relationship highlights the importance of mental health as an essential part of overall health. References Alotiby, A. (2024). Immunology of Stress: A Review Article. Journal of Clinical Medicine, 13(21), 6394. Segerstrom, S. C., & Miller, G. E. (2004). Psychological Stress and the Human Immune System: A Meta-Analytic Study of 30 Years of Inquiry. Psychological Bulletin, 130(4), 601–630. Morey, J. N., Boggero, I. A., Scott, A. B., & Segerstrom, S. C. (2015). Current Directions in Stress and Human Immune Function. Current Opinion in Psychology, 5, 13–17.