Answer:
It is because of the link between the brain and the immune system
Explanation:
Psychoneuroimmunology is the study of the effect of the mind on health and resistance to diseases. According to research in the field of psychoneuroimmunology, upsetting thoughts and emotions may have a negative influence on health because of the link between the brain and the immune system. Endocrine glands inside the body is responsible for many important functions and the hormones that this gland secretes have direct link with nervous system.
