Psychoneuroimmunology is the study of the interaction between psychological processes, the nervous system, and the immune system. A study led by Professor Shamgar Ben-Eliyahu found that psychological and physiological stress throughout surgery impairs immune system functioning, which can promote cancer recurrence. Blocking stress hormones before and after surgery through drugs was shown in animal models to reduce cancer metastases and potentially increase long-term survival rates in cancer patients by up to 300% by boosting the immune system.