Emotions like fear, that weakens our immune system and can cause cardiovascular damage, gastrointestinal problems such as ulcers and irritable bowel syndrome, and decreased fertility and sadness, which increases your risk of a number of diseases and other conditions by, for example, increasing levels of stress hormones such as cortisol or adrenaline, this leads to difficulty to fight infections. Scientists are not sure of how having positive thoughts help the system work very well, but they think this is connected to the prefrontal cortex on the brain.
Emotions that impact the Immune System
Anonymous . (2016). Impact of Fear and Anxiety. April 19, 2020, de University of Minnesota Sitio web: https://www.takingcharge.csh.umn.edu/impact-fear-and-anxiety
Anonymous. (2017). How depression affects your body. April 19, 2020, de WebMd Sitio web: https://www.webmd.com/depression/how-depression-affects-your-body#1