Introduction Psychological stress is considered one of the major factors affecting overall human health, as scientific evidence indicates that chronic stress can negatively influence immune system function. With the increasing pace and demands of modern life, understanding the relationship between stress and immune responses has become an important topic in psychiatry, immunology, and preventive medicine. Definition of Psychological Stress Psychological stress is defined as a physiological and psychological response that occurs when an individual is exposed to situations that exceed their ability to cope. Stress may be acute (short-term) or chronic (long-term), and each type has different effects on body organs and vital functions. Mechanism of Stress Effects on the Immune System When exposed to stress, the hypothalamic–pituitary–adrenal (HPA) axis is activated, leading to the secretion of stress hormones such as: Cortisol Adrenaline and noradrenaline Under normal conditions, cortisol regulates inflammation; however, when its levels remain chronically elevated, it can cause: Suppression of the production of certain white blood cells Reduced activity of natural killer (NK) cells Impaired antibody formation Altered inflammatory cytokine responses As a result, the body’s ability to resist infections and recover from illness declines. Associated Health Effects Studies have shown that chronic stress is associated with: Increased susceptibility to respiratory infections Delayed wound healing Exacerbation of autoimmune diseases Weakened response to vaccines Higher likelihood of relapse in some chronic conditions While short-term acute stress may temporarily stimulate immune activity, prolonged stress leads to long-term functional exhaustion of the immune system. Factors Influencing the Severity of Impact The effect of psychological stress on immunity varies according to several factors, including: Age and overall health status Lifestyle habits (sleep, diet, physical activity) Social and environmental support Genetic predisposition Individual coping strategies and resilience Strategies to Reduce Negative Effects Research indicates that lifestyle improvements can strengthen immunity in individuals exposed to chronic stress. Helpful strategies include: Regular physical activity Relaxation techniques, deep breathing, and meditation Adequate sleep A balanced diet rich in antioxidants Psychological and social support Time management and stress-reduction practices Conclusion It is evident that psychological stress—particularly chronic stress—plays a significant role in weakening immune function through complex hormonal and neural mechanisms. This highlights the importance of adopting preventive programs that promote mental and behavioral well-being, as they contribute directly to maintaining immune balance and protecting against disease. AL_mustaqbal University is the first university in Iraq