Stress is a survival mechanism that evolved to protect us from danger. One familiar stress hormone, adrenaline (that jolt you feel if you fall asleep and drift across your freeway lane,) helps you survive by causing your heart to race, lungs to open, pupils to widen, and by shutting down non-essential functions like digestion.
A second stress hormone is cortisol and it generates high blood pressure, high glucose, salt retention…in short, the physiology of running away from something trying to eat you.
Every night, Telomerase tries to repair your stem cells, but the stress-induced hormone, cortisol, inhibits telomerase activity, as shown in this study, causing your immune function to be ground down, and other stem cells to fail.
Here is a video explaining the link between stress and illness: